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Review ArticleNanocomposite-Based Bulk Heterojunction Hybrid Solar Cells

Bich Phuong Nguyen12 Taehoon Kim12 and Chong Rae Park12

1 Carbon Nanomaterials Design Laboratory Global Research Laboratory Research Institute of Advanced MaterialsSeoul National University Seoul 151-744 Republic of Korea

2Department of Materials Science and Engineering Seoul National University Seoul 151-744 Republic of Korea

Correspondence should be addressed to Chong Rae Park crparksnuackr

Received 30 August 2013 Accepted 20 November 2013 Published 8 January 2014

Academic Editor Sung Jin Kim

Copyright copy 2014 Bich Phuong Nguyen et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Photovoltaic devices based on nanocomposites composed of conjugated polymers and inorganic nanocrystals show promise forthe fabrication of low-cost third-generation thin film photovoltaics In theory hybrid solar cells can combine the advantages of thetwo classes of materials to potentially provide high power conversion efficiencies of up to 10 however certain limitations on thecurrent within a hybrid solar cell must be overcome Current limitations arise from incompatibilities among the various intradeviceinterfaces and the uncontrolled aggregation of nanocrystals during the step in which the nanocrystals are mixed into the polymermatrix Both effects can lead to charge transfer and transport inefficiencies This paper highlights potential strategies for resolvingthese obstacles and presents an outlook on the future directions of this field

1 Introduction

Hybrid solar cells combine both organic and inorganic semi-conductors in an active layer such that the organic or polymersemiconductor serves as the electron donor and transportsphotogenerated holes whereas the inorganic semiconductoraccepts and transports electrons [1ndash6] Theoretically the hy-brid photovoltaic devices (HPVs) are expected to achieve ahigh power conversion efficiency (PCE) because they com-bine the advantageous characteristics of polymers and nano-crystals (NCs) including the flexibility light weight and lowfabrication costs of polymer materials [7ndash9] and the highelectron mobility size-dependent optical properties [10 11]and physical and chemical stability of inorganicNCs [12] Un-fortunately the PCE values obtained thus far in hybrid devi-ces have not exceeded 4 under simulated air mass (AM) 15illumination [13] The main barriers to a higher PCE arethought to be an inefficient exciton dissociation at the donoracceptor (DA) interface [14ndash16] inhibition of recombination[17 18] and poor charge transport to the electrodes [19ndash21]Therefore the design of compatible surfaces accounting forthe different chemical properties of the organic and inorganicmaterials and control over the phase separation of the com-posites are crucial for achieving rapid and high-yield charge

separation at the DA interface and for promoting chargetransport and collection at the electrodesThree distinct strat-egies have been explored toward improving the interfacedesign in the nanocomposite materials to enable hybrid solarcells to achieve highPCEThefirst approach ligand exchangeuses amix of polymers and inorganicNCsprepared via colloi-dal synthesis approaches The second strategy grafting uti-lizes the grafting of a polymer fromonto the NCs yieldingpolymerNCs nanocomposites with improved grafting den-sity The third strategy direct NC growth involves the use ofa molecular precursor to the inorganic semiconductor dis-solved together with the polymer in a common solvent andthis solution may then be used to deposit the photoactivelayer

Improving the photovoltaic efficiency requires a clearunderstanding of the structure-properties relationship there-fore we focus here on one type of hybrid solar cell hybridbulk heterojunction solar cellsThis paper provides the readerwith insight into the basic principles underlying these devi-ces and discusses the current state-of-the-art in the threesynthetic strategies mentioned above A goal in this field is tounderstand the crucial parameters that are responsible forHPVs performance Motivated by the rapid growth and de-velopment of this field this review describes the recent

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2014 Article ID 243041 20 pageshttpdxdoiorg1011552014243041

2 Journal of Nanomaterials

advances and progress toward device improvement An out-look is provided on the futurematerials and technologies thatare likely to guide the future directions of research

2 Hybrid Solar Cells

21 Definitions ldquoHybridrdquo refers to the association of at leasttwo components of distinctly different chemical natures themolecular-level distribution of which components areachieved either through simplemixing or through linking thecomponents together via specific interactions such as cova-lent coordination ionic or hydrogen bonds Each hybridcomponent possesses its chemical identity and can exist inde-pendently of the hybrid material [22]

A bulk heterojunction is by definition a homogeneousblend of a p-type and an N-type semiconductor (donoracceptor) Organic photovoltaic devices (OPVs) based onblends of conjugated polymers and fullerenes form interpen-etrating donoracceptor networks and have been used in pro-totype bulk heterojunction geometry applications Bulk het-erojunctions in polymer-inorganic hybrid solar cells may beformed by replacing the fullerenes which act as organicnanoparticles (NPs) with inorganic semiconductors as elec-tron acceptors for dispersal in the polymermatrix NCs basedon metal oxides (ZnO [23ndash25] TiO

2[26ndash28]) group IIndashVI

(ZnS [29 30] ZnSe [31] CdTe [32ndash34] CdS [35ndash37]) groupIIIndashV (GaAs [38 39] InP [40]) group IVndashVI (PbSe [41] PbS[42ndash44]) group IV (Si [45 46]) CuInS

2[47 48] CuInSe

2

[49] have been tested for their utility as electron acceptors

22 Device Structure and Working Principle NCspolymerbulk heterojunction hybrid solar cells usually have devicearchitecture similar to those of organic solar cells (Figure 1)Anodes are often prepared by depositing indium tin oxide(ITO) which is conductive and transparent and which dis-plays a highwork function onto a flexible plastic or glass sub-strateThe conducted polymer poly(34-alkenedioxythiophe-nes)poly(styrenesulfonate) (PEDOTPSS) provides an anodebuffermaterial that enables efficient hole extraction Photoac-tive layers may be prepared by spin-coating a NCpolymerblend solution onto an ITO substrate to form a thin film 100ndash200 nm thick A top metal electrode (eg Al Ag and Ca)is then vacuum-deposited onto the photoactive layer as thecathode

As with OPVs the conversion of light energy into elec-tricity takes place in fourmain steps photon absorption exci-ton diffusion charge transfer and charge carrier transportand collection (Figure 2) Both organic semiconductor mate-rials and inorganic NCs can absorb incident light and createbound electron-hole pairs called excitons The excitons dif-fuse to the DA interface and then dissociate into free-chargecarriers The excitons dissociate at the interface if the energylevels of the NCs and the polymer are properly aligned Thischarge transfer process is necessary for creating a free-chargercarrier After charge separation the electrons and holes aretransported to their respective electrodes through percolatingpathways The holes are transported through the conjugated

PEDOTPSSITO substrate

NCspolymer

Metal cathode

NCs

Polymer

+ minus

C6H13

S n

Figure 1 Schematic diagram showing the structure of a typicalNCpolymer hybrid solar cell

Polymer phase

NCs phaseh

minusminus

minus

1

2

34

4

+

+

+

Figure 2 Schematic diagram showing the photocurrent generationmechanism in a bulk heterojunction hybrid solar cell excitongeneration (1) exciton diffusion (2) charge transfer (3) chargecarrier transport and collection (4)

polymer and the electrons are transported through theinorganic semiconductor (Figure 2)

The mechanism can be broken down into a number ofsteps each of whichmay be characterized by an efficiency (120578)which is defined on a scale of 0 to 1 The successful operationof a photovoltaic device requires that most or all of the stepsare characterized by 120578 close to 1 The overall efficiency of theconversion of incident photons to current that is the externalquantum efficiency (EQE) can be written as

EQE (120582 119881) = 120578119860(120582) times 120578diff times 120578diss (119881) times 120578tr (119881) times 120578cc (119881)

(1)

where 120582 is the wavelength of the incident light and 119881 is thevoltage across the cell120578119860(120582) is the photon absorption yield Most polymers have

a bandgap larger than 2 eV which limits the light absorptionrange As such materials with a complementary absorptionspectrum in the near-infrared range [42] or ultraviolet range[57 58] could be conjugated to the inorganic NCs120578diff is the exciton diffusion yieldThe fraction of excitons

that reach the DA interface is determined by the exciton dif-fusion length and the location at which an exciton is createdwith respect to the nearest dissociation center The excitondiffusion length in both anOPVand anHPV is in the range of10ndash20 nm for a conjugated polymer [59ndash61]

Journal of Nanomaterials 3

120578diss is the exciton dissociation yield which is the ratio ofthe number of excitons that dissociate to free charges at a DAinterface to the total number of excitons that reach the DAinterface In a well-designed HPV the donor and acceptormaterials must have suitably been aligned with energy bandsthat enable exciton dissociation and provide a high overallelectrochemical potential These requirements constrain thetype and range of suitable donor and acceptor materials aswell as the interactions between these materials at the DAinterface [2 5]120578tr is the charge transport yield which is the ratio of the

number of free charge carriers transported to the collectingelectrode to the number of excitons dissociated at the het-erojunction interface Donor and acceptor materials are bothrequired for a highly efficient percolated network that spansthe entire active layer to provide efficient charge transportStructural defects impurities and the crystallinity of both thedonor and acceptor materials in the active layer can cause thecharge carriers to become trapped and recombine whichreduces the transport efficiency [2] Device architecture alsorequire that each phase is continuous throughout the activelayer to provide a pathway for rapid carrier transport to therespective electrodes120578cc is the charge collection yield This parameter repre-

sents the ability of the charges to transfer from the photoac-tive layer to the electrodes 120578cc depends on the energy levels ofthe active layer and the electrode as well as the interface pro-perties between them [2]

A lowphotocurrent in anHPV results from limitations onthe parameters 120578diss and 120578tr Our research group has appliedsignificant efforts toward exploiting the high internal surfacearea and nanoscale dimensions of inorganicorganic nano-composites as a means for overcoming the limitations of cur-rent HPVs

The power conversion efficiency is one of themost impor-tant parameters for characterizing the solar cell performanceFigure 3 shows a schematic diagram of the current density-voltage (119869-119881) characteristics of a typical hybrid solar cell inthe dark and under illumination The PCE is given by

PCE =119875119898

119875in=119869SC times 119881OC times FF119875in

(2)

where 119875119898is the maximum power point 119875in is the incident

light density and FF is the fill factor which is defined as theratio of 119875

119898to the product of 119869SC and 119881OC

FF =119875119898

119869SC times 119881OC (3)

The 119869SC and 119881OC are two basic factors to determine the solarcell efficiency An understanding of the physical processesgoverning these two parameters is needed for the design ofnew materials and device configurations that would yield ahigh conversion efficiency [3]119869SC the short-circuit current density depends on the inci-

dent light intensity and the absorption spectrum of the activematerials 119869SC is given by [62]

119869SC = 119890intinfin

119864119892

119873ph (119864) times EQE (119864) times 119889119864 (4)

Curr

ent d

ensit

y

Voltage

Dark

Under illumination

Pmax VOC

JSC

Figure 3 Current density-voltage (119869-119881) characteristics of a typicalsolar cell in the dark (dashed line) and under illumination (solidline)

where 119873ph is the spectral photon flux of the incident light119864119892is the bandgap of the active layer and 119864 is the photon

energy Although inorganic acceptors can absorb light at cer-tain wavelengths the majority of light absorption usuallytakes place in the donor polymer Dayal et al [13] reportedthat the contribution of light absorption from CdSe in apoly[26-(44-bis-(2-ethylhexyl)-4H-cyclopenta[21-b34-b1015840]dithiophene)-alt-47-(213-benzothiadiazole)] (PCPDTBT)CdSe hybrid containing about 90wt CdSe nanotetrapodwas only 34 Similarly TiO

2and ZnO only absorb sunlight

in theUVrangewhich is characterized by a lower photonfluxthan the visible or IR ranges The calculations may thereforebe simplified by assuming that light absorption only occurs inthe polymer119881OC is the open-circuit voltage119881OC in polymer inorganic

hybrid solar cells was found to depend on the difference bet-ween the polymerrsquos highest occupied molecular orbital(HOMO) and the inorganic acceptor conduction band [71]Due to the quantum confinement effect the bandgap of inor-ganic semiconductors varies as a function of particle sizeleading to a shift in the conduction band energy level [72]which can also affect the 119881OC The 119881OC of a hybrid solar cellcan be increased by either moving the polymer HOMO far-ther away from the vacuum level or pushing the inorganicacceptor conduction band closer to the vacuum level whileretaining an energy offset between the polymerrsquos lowest unoc-cupied molecular orbital (LUMO) and acceptor conductionband larger than the exciton binding energy (119864

119887) [3] In a bulk

heterojunction solar cell the theoretical maximum 119881OC canbe described as

119881OCmax = 119864119892DA = 119864119892D minus (LUMOD minus LUMOA) (5)

The conversion efficiencymay be increased by optimizing thebalance between the donor gap (which mainly determines119869SC) and the donor conduction band (which mainly deter-mines 119881OC)


Table 1 Overview of hybrid solar cells prepared using nanocomposites comprising organic and inorganic materials

Hybrid system Aim of the work Strategyapproach PCE () Summary of findings Reference

ITOPEDOT PSSCdSe PCPDTBT (9 1 wtratio)LiFAl

Characterize the propertiesof an HPV prepared usingCdSe tetrapods and a lowbandgap polymer

Ligandexchange 319

Low bandgap polymersplayed an important role inimproving the solarharvesting efficiency andthe contribution of the NCstowards the PCE

Dayal et al(2010) [13]

ITOPEDOT PSSCdSe PCPDTBTCaAg

Demonstrating chargetransport enhancementusing CdSe nanorods (NRs)and quantum dots (QDs)

Ligandexchange 36

A NR network incombination with smallQDs produced highlyinterconnected pathwaysfor electron transportwithin the polymer matrixThis structure enhancedcharge transport andreduced recombination

Jeltsch et al(2012) [20]

ITOPEDOT PSSTiO2 MEH-PPVAl

Characterize the propertiesof an HPV prepared usingMEH-PPV TiO2 incombination with theligands oleic acid (OA)n-octyl-phosphonic acid(OPA) or thiophene (TP)

Ligandexchange 0157

TiO2 capped withthiophenol yielded a higherPCE and proved to be oneof the best ligands forfabricating HPVs

Liu et al (2008)[50]

ITOPEDOT PSSCdS P3HTAl

Carrier mobilityenhancements could beaccomplished by improvingthe blend interface withoutthe use of a surfactant

In situ growth 29

P3HT acts as a moleculartemplate for CdS NCgrowth The aspect ratios ofCdS NRs were controlledaccording to the cosolvent(dichlorobenzene (DCB)and dimethyl sulfoxide(DMSO)) which inducedconformational variationsinto the P3HT chainsEnhanced chargeseparation at the interfacesuggested electroniccoupling between theP3HT and CdScomponents The highlyinterpenetrating networkincreased charge transport

Liao et al(2009) [51]

ITOPEDOT PSSZnO P3HTAl

Characterize the nanoscaleP3HT ZnO bulkheterojunction 3Dmorphologies usingelectron tomography

In situ growth 2

The 3D exciton diffusionequation was solvedphotophysical data werecollected and the 3Dmorphology wascharacterized as a functionof film thickness Chargegeneration and chargetransport were identified aslimiting the deviceperformance

Oosterhout et al(2009) [52]

FTOPEDOT PSSP3HT CdSeP3HTAl

A P3HT CdSe compositewas prepared using theP3HT ligand as a CdSesurface cap The quantity ofP3HT in the precursorsolution was found to affectthe optical properties

In situ growth 132

The quantity of P3HT inthe reaction did not affectthe shape or phase of theCdSe superstructuresamples although it didaffect the photoabsorptionand photoluminescenceemission intensities

Peng et al(2013) [53]


Table 1 Continued


ITOPEDOT PSSCdSe P3HTAl

HPVs were fabricated bygrafting P3HT onto theCdSe nanoparticles (NPs)

Grafting 11

The end functional P3HTenhanced the performanceof the P3HT CdSe HPV byincreasing the dispersion ofCdSe without the need for asurfactant

Liu et al (2004)[54]

A device was fabricatedusing pristine ZnOZnO P3HT compositesand ZnO didodecyl-quaterthiophene (QT)composites

HPVs were prepared usingP3HT and single ZnOnanowires (NWs) graftedQT

Grafting 0036

Oligothiophene andpolythiophene were graftedonto the ZnO NWs toproduce p-nheterojunctions Theefficiencies of theZnO P3HT compositeswere high (0036)compared with theefficiencies of other devices

Briseno et al(2010) [55]

ITOPEDOT PSSCdS P3HTBCPMgAgwhere BCP isbathocuproine

Solvent-assisted chemicalgrafting and ligandexchange were used tocontrol the P3HTCdSinterface and the CdS QDinterparticle distances

Grafting 41

P3HTCdS-grafted NWstructures prepared bysolvent assistance(dichlorobenzene andoctane) can increase theelectronic interactionsbetween the CdS QDs andthe P3HT NWsLigand exchange reducesthe distances among CdSQDs leading to efficientlyseparated charge transfer

Ren et al (2011)[56]

3 State-of-the-Art in HybridPhotovoltaic Materials

Bulk heterojunction hybrid solar cells lag behind the fullerenederivative-based OPVs with respect to device performancedue to the limits of the current Enhanced PCEs in bulk het-erojunction HPVs may be achieved by increasing the DAinterface area which improves the efficiency of exciton disso-ciation and charge transfer and by creating interpenetratingbicontinuous percolating pathways for effective charge trans-port to the corresponding electrodes Therefore interfacialbehavior and nanoscale morphology of an active layer arethese critical performance factors for HPVs Increase of DAinterface and control over the nanoscalemorphology of com-posite layer are required however many issues must be over-come First blending inorganic NCs and organic conjugatedpolymers remains challenging Dispersing inorganicNCs in apolymer matrix requires the presence of a capping agent thatprevents particle aggregation but usually suppresses excitondissociation and charge transport Another issue is thatcharge transport through the composite phase is both highlysensitive to the NCs structure and to the presence of trapstates within the NCs Fortunately significant progresstoward enhancing the PCEs of HPVs has been made by opti-mizing colloid synthesis [73ndash76] and self-assembly [77 78]procedures for preparing the NCs as well as by tuning theshapes of the NCs (dots [79ndash81] rods [82ndash84] tetrapods

[13 85 86] hyperbranched structures [87] wires [56] etc)These approaches seek to prepare continuous pathways forcharge transport and reduce the prevalence of carrier traps onNCsMoreover quantum size effects [72]may be harnessed totune the device performance by designing the relative align-ment of the energy levels in the donor and acceptor materials[84 88]

In this review we focus on three strategies for improvingthe PCE in an HPV ligand exchange grafting and direct NCgrowth These methods have been used to improve the poly-mersNC interface properties and to control the blend mor-phology The characteristics of bulk heterojunction HPVdevices are summarized in Table 1

31 Nanocomposites Prepared by Ligand Exchange ChemistryTwo distinct routes may be taken to produce NCs physicalapproaches in which the NCs are fabricated by lithographicmethods ion implantation ormolecular beam deposition orchemical approaches in which the NCs are synthesized bycolloidal chemistry in solutionThe unique optical and electr-ical properties of colloidal semiconductor NCs have attractedsignificant interest and have been explored in a variety ofapplications such as optoelectronic devices [89] sensors[90] and photovoltaics [2 6] Colloidal NCs synthesized inorganic media (eg alkyl thiol amines phosphines or phos-phine oxides) are usually soluble in common organic solvents


and can be mixed together with conjugated polymers whichtend to be soluble in the same solvents Most organic surfact-ants and ligands tend to be insulated which impedes chargetransfer between the polymers and theNCs and impedes elec-tron transport between adjacent NCs In the absence of passi-vating ligands it is difficult to control the composite mor-phology because the inorganic NCs tend to be poorly solublein polymer matrices The performances of such devices aresignificantly reduced

In 1996 Greenham et al investigated the effects of a QDcapping ligand on the initial charge transfer process betweena polymer and the CdSe QDs by simply and physically mix-ing the polymer and NCs [91] By considering effective lumi-nescence quenching as amanifestation of the exciton dissoci-ation these authors observed that the quenching of the pho-toluminescence (PL) of poly[2-methoxy-5-(2-ethylhexy-loxy)-14-phenylenevinylene] (MEH-PPV) did not occurwhen 4 nmdiameter CdSeNCs were capped with a long alkylchain such as trioctylphosphine oxide (TOPO) but that PLquenching was efficient after treatment with pyridine Theauthors proposed that the lack of PL quenching was due tothe ligand-covered NCs creating a barrier layer that preven-ted the NCs from approaching the polymer (reducing theinterfacial area)The 11 A thick TOPO alkyl barrier surround-ing the CdSe NCs was sufficient to prevent charge transfer[91] Long chain ligand-cappedNCs could be exchanged withshort chain ligands to enhance the interface area

Pyridine ligand exchange is commonly used to improvethe efficiency of hybrid solar cell performance Long alkylchain-capped NCs are generally washed with methanol sev-eral times and then refluxed in pure pyridine at the boilingpoint of pyridine for 24ndash48 h Pyridine treatment appears toreplace the insulating ligand and the effects of pyridine ex-change have been examined in the context of poly(3-hexyl-thiophene) (P3HT)CdSe [79 92] PCPDTBTCdSe [13] andMEH-PPVCdSe [81] bulk heterojunction devices Thesestudies indicated that replacing the insulating ligands on theNCs with pyridine favored electron transport between NCsby reducing the insulating effects of the ligand andmore inti-mated the contact with NCs and polymer leading to impro-ved 119869SC 120578diss and 120578tr Pyridine ligand exchange is a standardtechnique for preparing NPs suitable for polymerCdSe solarcells It is not universally suitable however because somepolymers (such as P3HT) are not soluble in pyridine and themechanism of ligand exchange process is still unclear [92]

The identity of the capping ligand strongly affects thedegree of phase separation and the morphology of a NCpolymer thin film A series of capping ligands (tributylamineoleic acid pyridine stearic acid and butylamine) [63 93]have been tested in a study of their effects on the morphol-ogy and 119869-119881 characteristics of a P3HTCdSe HPV deviceThehighest PCE (up to 18) was obtained by using butylamine-capped CdSe NPs with a ww mixing ratio of 12 1(CdSe P3HT) and a posttreatment temperature of 110∘CButylamine has the advantage of providingNCs that are solu-ble in typical polymer solvents and of inducing the formationof a composite phase with small domains on the order of theexciton diffusion length (Figure 4) Therefore there is con-siderable room for engineering ligands that can improve

101

100

10minus1

10minus2

10minus3

10minus4

10minus5

minus10 minus05 00 05 10

Voltage (V)

Curr

ent d

ensit

y (m

(e) Tributylamine(d) Oleic acid(a) Butylamine

(b) Stearic acid(c) Pyridine

(a)

(b)

(c)

(d)

(e)

A cm

minus2)

Figure 4 AFM images and 119869-119881 characteristics of CdSe NCsP3HTfilms prepared using various capping ligands (a) butylamine (b)stearic acid (c) pyridine (d) oleic acid and (e) tributylamineReprinted from [63] with permission from Elsevier

exciton separation enhance the charge transfer efficiency atthe polymerNC interface and form percolating electrontransport pathways to the cathode [94]

After ligand exchange with short chain ligand NCs tendto aggregate and precipitate out of organic solvents whichcomplicate the preparation of stable mixtures of NCs andpolymers Zhou et al applied a novel postsynthetic treatmentmethod to spherical CdSe QDs in which the NCs werewashed with hexanoic acid without inducing ligand exchange[64] The PL quenching TEM and dynamic light scattering(DSL) measurements suggested that the ligand sphere hadbeen reduced during the washing step thereby improving thephotovoltaic device efficiency (Figure 5) One advantage ofthis approach is that the QDs retained their solubility afteracid treatment which allows a high concentration of theCdSeQDs in P3HT (increasing 120578diss)The large amount of CdSe ledto the formation of efficient percolation networks duringannealing of the photoactive composite film Solar cellsachieved efficiencies of 20 which is the highest value yetreported for devices prepared using quasispherical CdSe NPsconjugated with a polymer

Another strategy for reducing the insulating properties ofthe ligand in a polymerNC hybrid material involves theapplication of a thermal treatment to remove weakly boundligands [43 65] Seo et al [65] replaced the TOPO ligand onCdSe NCs with tert-butyl N-(2-mercaptoethyl) carbamateligands for the preparation of a P3HTCdSe BHJ device byusing a solvent exchange reactionThemixture in a blend sol-vent was then coated onto the substrate After heating above200∘C the ligand was thermally cleaved with isobutene andcarbon dioxide evaporated from the film The remaining 2-mercaptoethylamine ligands were considerably smaller thanthe original ligand and the electrical characteristics of thedevice improved due to enhanced contact between the CdSeparticles and the polymer (Figure 6) These processes in-creased 120578tr and 120578diss by forming better contact with the donorThe PCE could be increased from 021 to 044 by increas-ing the heat treatment temperature from 150∘C to 250∘C


Curr

ent d

ensit

y (m

Ac

m2)

6

3

0

minus3

minus60 200 400 600

Voltage (mV)

(d)

VOC = 623mV

JSC = 58mAcm2

FF = 056

Eff = 20

(c)

H

HHN

N

O

O

OAcid

salt+

H2N

(a) (b)

100nm 100nm

OHNH2

NH2

HDA ligand sphere

H2 QDΔ

QD

CH3(CH2)3CH2

CH3(CH2)3CH2

Figure 5 TEM images of hexadecylamine (HAD)-capped CdSe NCs before (a) and after washing with hexanoic acid (b) Proposed processfor surface ligand removal (c) 119869-119881 characteristics of a device prepared with 87 CdSe NPs (d) Reprinted from [64] with permission fromthe American Institute of Physics

QDS

S SS

S

SS S

SS

SSS

NH2

NH2

NH2

NH2H2N

H2N

H2N

H2NHNHN

HN

H

HN N O

OO

O

OO

OO

O

O

SO

ONHSO

ONH

S

OO NH

Δ

+ carbon dioxideand isobutene

(a)

100∘C (photo)

100∘C (dark)

200∘C (photo)

200∘C (dark)

Curr

ent d

ensit

y (m

Ac

m2)

Curr

ent d

ensit

y (m

Ac

m2)15

10

05

00

minus05

minus10

minus1500 02 04 06 08 10

Voltage (V)

00 02 04 06 08 10Voltage (V)

100

10minus1

10minus2

10minus3

(b)

Figure 6 (a) Schematic illustration of the thermally induced deprotection of the tert-butyl N-(2-mercaptoethyl) carbamate ligand linked tothe surface of a CdSe NC (b) 119869-119881 characteristics of a device containing 90 CdSe NPs The inset shows the photocurrent characteristics ona semilogarithmic scale Reprinted from [65] with permission from the American Institute of Physics

which increased 119869SC and FFThis approach was generally lesssuccessful than the replacement of TOPO with pyridine be-cause the glass transition temperature 119879

119892of P3HT is below

200∘C [95] The use of ligands with a low boiling point andweak attachment properties to NCs could potentially lead tothe facile preparation of multilayer devices

The side chains of the conjugated polymers play an impor-tant role in regulating charge transfer [96] Enhanced chargetransfer at the interface of a composite may be achieved bypreparing a polymerNC blend via ligand exchange in which

the insulating capping ligand on theNC surfaces is exchangedwith a functionalized polymer This exchange process relieson the use of polymers having strongly coordinating func-tional groups that can anchor directly on theNC surfaces Liuet al prepared hybrid materials comprising NCs and a P3HTpolymer matrix using an end-functional amino group [54](Figure 7) The original surface ligands capped onto the NCsurface were replaced with pyridine The CdSe nanorods(NRs) were then mixed with either a nonfunctionalizedP3HT polymer (polymer 1) or an amino end-functionalized


S CNS CNSn

CNSS

H

C6H13

CH2NH2SS

C6H13

Hn n

(1) LDA(2) (CH3)3SnCl

(2) H2O

tolueneDMF (Pd(PPh3)4 120∘C

4 1)

SH Br

C6H13

n

1

2

3 4

(1) LiAlH4THF reflux

(a)

100nm 100nm

(b)

Figure 7 (a) Synthesis of P3HT using an amino end-functionalized polymer 4 (b) TEM images of CdSe (40wt)polymer 1 (left) and CdSe(40wt)polymer 4 (right) Reprinted with permission from [54] Copyright 2004 ACS

P3HT polymer (polymer 4) Interestingly the amine-func-tionalized P3HT provided a PCE of 15 whereas the devicefabricated using the nonfunctionalized P3HT yielded a PCEof 05 These results suggested that the temporary pyridineligands were exchanged with the polymeric ligands throughcovalent interactions that enhanced themiscibility of theNRsin the P3HT Chemical linkages between the polymer and theNCs offer a route to improving the NP dispersion in solventsand the electronic interactions between the polymer andNCs

However the amine-terminated P3HT is not a sufficientlystrong functional group to fully passivate the CdSe surfacecapped with TOPOwithout the need for pyridine as an inter-mediate ligand To avoid the intermediate step which mayaffect the quality of the final compositematerial a strong typeof functional group polymer was used to directly be ex-changed with the original ligand In fact the hybrid TOPO-capped CdSe NPs were successfully embedded in the phos-phoric acid-terminated P3HT by simply mixing the compo-nents in chloroform and permitting the reaction to proceedovernight [97] The success of bonding between P3HT andCdSe was confirmed by 1H NMR A total of 50 P3HT chainswere estimated as being present on one CdSe NP based on ananalysis of the absorption spectrumThe PL quenching of thegrafted P3HT and CdSe NPs clearly indicated the occurrence

of charge transfer at the interface suggesting that the elec-tronic interactions between the functional components couldbe facilitated by the end-functionalizing polymers havingstrong binding groups

In addition to theCdSeNCsmetal oxides such as ZnOorTiO2 were tested as candidate materials in green solar cell

devices TiO2NRs covered with TOPO ligands were synthe-

sized for use in a hybrid solar cell Although the PCEs of thesedevices were 114 for the pyridine ligand-capped NRs [98]or 003 for the dye-cappedNRs [57 99 100] the charge sep-aration and transport efficiency improved upon the removalof the insulating surfactant in the hybrid materials

In 2004 Beek et al [101] reported the performance of bulkheterojunction hybrid solar cells fabricated based on ZnONCs and poly[2-methoxy-5-(3101584071015840-dimethyloctyloxy)-14-phenylenevinylene] (MDMO-PPV) These cells yielded aPCE of 14 at AM 15 The ZnO NPs could be dispersed indichloromethane chloroform or chlorobenzene up to a con-centration of 70mgmLminus1 without the need for additional lig-ands or surfactants However the PCEs of the metal oxidesremained low due to the presence of surface defects and largeZnONCaggregates which increased the recombination Twoyears later Beek et al reported their work on ZnO NPP3HTbulk heterojunction HPVs The highest PCE of these deviceswas 120578 = 09 [102] The measured PCE was lower than that


obtained for MDMO-PPVZnO although the hole mobilityof P3HTwas expected to be higher than that ofMDMO-PPVThe presence of ZnO may have influenced the crystallizationof P3HT because the ZnO surface was hydrophilic and thesmall number of ZnO clusters could not form charge trans-port pathways to the electrodes [103] Many approaches toZnO surface modification such as using surfactants [104ndash106] anchoring molecules [107ndash109] dipolar molecules[110 111] and dyes [112] are available to improve the dis-persion of ZnO in a polymer matrix However surface-modified ZnO does not necessarily lead to a higher PCE be-cause the poor phase separation can hinder charge transportControl over particle solubility and the blendmorphology re-mains a key requirement for improving ZnOpolymer deviceperformances

Further extension of the absorption spectrum into theinfrared regime could be achieved using PbS or PbSe NCsZhang et al [113] demonstrated HPVs based on PbS andMEH-PPV They compared the photovoltaic performance ofMEH-PPV composite device containing eitherOA-capped oroctylmaine-capped nanocrystals after postannealing thecomposite layer at 220∘C The improvement in the photovol-taic performance of device using octylamine ligand-cappedPbS NCs showed an 200-fold increase in J

119878119862 while devices

using OA-capped NCs do not The thermogravimetric ana-lysis (TGA) data showed a 5 weight loss after heating to200∘C for octylamine-capped NCs while no appreciableweight loss was observed for OA-capped NCs below 300∘CThese results suggested that a certain amount of octyl-amine ligand is removed from the film during the annealingprocess (the boiling point of actylamine is 175∘C) thus im-proving the efficiency of the charge transfer at the interfaceUnfortunately the device efficiency was very low because ofthe large ligand which is still surrounding the PbS NPs andunsuitable relative alignment of the energy levels in the donorand acceptor Noone et al [114] utilized a new polymer poly(23-didecyl-quinoxaline-58-diyl-alt-N-octyldithieno[32-b2101584031015840-d]pyrrole) (PDTPQx) and the OA ligands of PbSNCs were replaced by butyl amine ligand This device ofPDTPQxPbS (1090 ww) exhibited PCE of sim055 Morerecently the blending OA-capped PbS NCs with a low band-gap polymer poly(26-(N-(1-octylnonyl)dithieno[32-b2030-d]pyrrole)-alt-47-(213-benzothiadiazole)) (PDTPBT)was directly exchanged with a short length cross-linkermole-cule 12-ethanedithiol Seo et al significantly improved thedevice efficiency to a high value of 378 [115]

In spite of the improvement in PbS-based hybrid solarcells the device engineering on PbSe-based HPVs has beendifficult with a low PCE of sim01 to date [41] Although theefficiency of HPVs based on PbSe is low it has been demon-strated that Pb(SeS) NCs based quantum dot solar cells showpromising efficiency up to 7 [116 117]

32 Nanocomposites Prepared via a Grafting Process Hybridmaterials may be prepared by grafting macromolecules ontoNC surfaces via specially designed linker ligands containingan anchor functionality (for NC binding) and an additionalreactive group capable of reacting with side- or end-func-tionalizedmacromoleculesThe grafting process was realized

as follows first the original NC surface ligands were replacedwith the linker ligands the grafting reaction was then carriedout according to the reactive group type in the linker ligandand in the grafting macromolecule An example of this proc-ess was discussed by Zhang et al [66] CdSe NRs were graftedto vinyl group-terminated P3HT groups via a p-bromo-benzyl-di-n-octylphosphine oxide (DOPO-Br) linker group(Figure 8) In the first step the original TOPO ligands wereexchanged with pyridine The pyridine ligands were then re-placed with arylbromide-functionalized phosphine oxidesThe grafting reaction was then carried out via Heck couplingbetween the vinyl-terminated P3HT The solid state PL mea-surement of the thin nanocomposite films revealed PL quen-ching of the P3HT which was indicative of charge transferbetween the P3HT and CdSe NRs

Bifunctional linker ligands have recently been tested fortheir utility as original NC ligands This strategy reduces thecosts and time needed for preparing hybrid materials by per-forming the grafting in a single stepwithout a ligand exchangestep The bifunctional ligand (ie DOPO-Br) contains aphosphine oxide group at one end similar to the phosphinegroup on the TOPO which anchors the linker to the QD sur-face and an arylbromide is present at the other end to enablegrafting to a macromolecule [118] CdSe QDs were grown inDOPO-Br to directly yield the DOPO-Br capped CdSe QDsThe PPV derivatives were synthesized by polymerizing 14-divinyl benzene with 14-dibromobenzene derivatives Poly(p-phenylene vinylene) (PPV) derivatives have been directlygrafted onto a DOPO-Br functionalized CdSe QD surface viaPd-catalyzedHeck coupling [67] (Figure 9) By replacing PPVderivatives the success obtained from grafting the vinyl-ter-minated P3HT to the DOPO-Br functionalized CdSe QDswas expected to apply for photovoltaic devicesThe end groupP3HT contacted the CdSe QDs and interacted with themdirectly to facilitate charge transfer from the P3HT to theCdSe at the interface PL quenching and the short fluores-cence lifetime of the P3HTCdSe composite compared to thecorresponding values obtained from P3HT alone confirmedthat the charge transfer was effective This system sufferedfrom someunfortunate drawbacks theDOPOcopolymeriza-tion conditions were difficult to be controlled and this strat-egy cannot be extended to the synthesis of CdSe NRs becausethe DOPO-Br capping group is not suitable for inducing thegrowth of CdSe NCs

Briseno et al reported a convenient method for directlyattaching end-functionalized polymers to NCs with bare sur-faces without the need for ligand exchange andor direct bi-functional ligand growth processes [55] P3HT and didode-cylquaterthiophene (QT) terminated with phosphonic esterand phosphonic acid respectively were chemically graftedonto an N-type ZnO nanowire (NW several micrometers inlength and 30ndash100 nm in diameter) via self-assembly of thesemiconductors onto the ZnO surface in the solution phase toyield an organic shell with a thickness of about 5ndash20 nm(Figure 10) A single NW solar cell was successfully preparedusing p-n coreshell NWs Although the PCE of the singleNW solar cell was low 0036 this device permitted the iso-lation and study of the parameters that affect bulk hybrid solarcell performance Increasing the P3HT layer thickness on


BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N

N Pd2(dba)3 P(tBu)3methyldicyclohexylamine

Ligand exchange

n

Poly(3-hexylthiophene)

Figure 8 Synthesis of the P3HT-CdSe NR composites by grafting with bifunctional ligands (thiol or phosphine oxide) followed by couplingof the vinyl-terminated P3HT to the arylbromide-functionalized CdSe NRs Reprinted with permission from [66] Copyright 2007 ACS

Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O

N-methyldicyclohexylamine tri-t-butylphosphine Pd(0) THF 50∘C

Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n

Figure 9 Grafting of PPV onto [(4-bromophenyl)methyl]dioctylphosphine oxide (DOPO-Br)-functionalized CdSe QDs by polymerizingfrom the crystal surface Reprinted with permission from [67] Copyright 2004 ACS

the ZnO surface significantly improved the performance ofthe NW device however the 119881OC in the single wire devices(119881OC = 04V) was larger than the value reported in the litera-ture 119881OC = 017V for a P3HTZnO bulk NW array devicesuggesting that the P3HTZnO interface in the grafted poly-mer was superior to the bulk spin-coated counterpart

To date the grafting approach offers a high grafting cov-erage density that increases the effective organicinorganicinterface to enable rapid charge separation The grafting ap-proach relies on the design of bifunctional ligands and func-tioned polymers that facilitate the controlled growth of NCsand the efficient grafting of NCs respectively However the


(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT

(1) nBuLi minus78∘C

(b)

Figure 10 Synthesis of end-functionalized (a) P3HT and (b) QT bearing a phosphonic ester or a phosphonic acid respectively Thesepolymers were subsequently self-assembled onto the ZnO NWs Reprinted with permission from [55] Copyright 2010 ACS

surface grafting and polymerization steps are usually com-plicated Excessive grafting reduces the efficiency of electrontransport between adjacent NCs thus controlling the surfacegrafting processes remains a challenge

33 Nanocomposites Prepared via an In Situ Process A newstrategy was developed for inducing NC growth in a polymermatrix in an effort to avoid organic capping ligands and im-prove charge transfer between the NCs and the organicmatrixThis approach relies on the dissolution of the NC pre-cursors in a solution containing the polymer and the NCs arethen grown in the polymer template This strategy has beenapplied to a variety of semiconductor NCs including TiO

2

[119] ZnO [120 121] PbS [44 70] CdSe [122] and CdS[51 69 94]

The in situ NC growth method was first tested by prepar-ing a TiO

2MDMO-PPV HPV in which titanium isopropox-

ide was used as the precursor A BHJ device was expected toprovide a higher efficiency than a bilayer device however theresults of the initial test did not confirm this assumption [123]

The low efficiency of the in situ blended devices could beexplained by the noncrystalline structure of the TiO

2semi-

conductor High-temperature annealing can produce crys-talline TiO

2 but the high temperatures are not compatible

with organic semiconductorsThis strategy was applied to the fabrication of ZnO

polymer HPVs because crystalline ZnO can be formed at lowtemperatures The work of Beek et al provides an instructiveexample of this approachThe photoactive layer composed ofZnOMDMO-PPV composites was prepared by spin-coatinga mixed solution containing the precursor diethylzinc andMDMO-PPV [120] During spin-coating diethylzinc wasexposed to moisture and formed Zn(OH)

2upon undergoing

spontaneous hydrolysis The thin film was then annealed at110∘C to yield an interpenetrating network of ZnO inside theMDMO-PPV These devices offered a PCE of 11 less thanthe value obtained for ZnO NPs mixed with MDMO-PPV(PCE = 16) however the 119881OC reached a high voltage of114 V Such a high voltage has not previously been reportedDegradation through breakage of the transvinyl bonds inthe PPV polymer upon mixing with the ZnO precursors


100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)

Figure 11 TEM images of blend layers composed of ZnOP3HT (a) or ZnOP3HT-E (b) Reconstructed volumes based on the electrontomography of the ZnOP3HT (c) and ZnOP3HT-E layers (d) Reprinted from [68] with permission fromWinley-VCHVerlag GmBHampCo

produced large undesirable effects on the charge carrier [121]Themore stable P3HT did not display changes in the absorp-tion spectra and hole transport properties during processingproviding a PCE of up to 14 for the ZnOP3HT deviceTheimproved photovoltaic performances mainly resulted fromthe large increase in the 119869SCThe highest PCE yet obtained foran ZnOP3HTHPV fabricated using this precursormethod is2 [52]

Oosterhout et al investigated the use of an ester-function-alized P3HT-E that was more compatible toward the hydro-philic ZnO NCs [68] The P3HT-E produced a much finerphase separation and a higher surface area upon blendingwith ZnO (Figure 11) 119869SC increased due to the enhanced 120578dissand 120578tr however better mixing in the ZnOP3HT-E compos-ite appeared to reduce the ZnO connectivity and hole mobil-ity in the polymer due to the lower degree of crystallinity inthe P3HT-E phase Only thin devices displayed current andPCE enhancements

HPVs fabricated using small bandgap poly(3-hexylselen-ophene) (P3HS) in combination with ZnO were expected toyield a higher PCE [124] however the PCE of ZnOP3HSwas04 due to the lower 119869SC The spectrally resolved externalquantumefficiencywas comparedwith the optical absorptionspectrum revealing that the amorphous P3HS regions werein direct contact with the ZnO NCs whereas the semicrys-talline P3HS phase contributed negligibly to the photocur-rent 119869SC therefore decreased due to a reduction in 120578diss Theauthors indicated that the interface in ZnOP3HS was disor-dered similar to the P3HT disorder observed in ZnOP3HT

devices The polymers rapidly degraded when mixed withdiethylzinc in solution [124]

Leventis et al introduced another in situ method for fab-ricating metal sulfide NPpolymer films [69] Metal xanthateprecursors were selected because they decompose at low tem-peratures into a metal sulfide generating only volatile sideproducts (eg H

2S COS C

2H4) The decomposition process

enabled the in situ growth of inorganic NCs in a relative fra-gile polymer host The CdS centers formed an extended net-work rather than particles which would have increased 120578trhad the materials not also vertically segregated thereby re-ducing 120578diss (Figure 12) The length scale of the phase seg-regation process depended strongly on the annealing temper-ature [125] An increase in the annealing temperature from105∘C to 160∘C led to a reduction in the sizes of CdS domainsembedded in the P3HTmatrix from 100 nm to below 40 nmA highly mesoporous structure formed to include intercon-nected CdS NP aggregates approximately 30ndash50 nm in diam-eter The resulting photovoltaic devices exhibited a PCE of217 The in situ thermal decomposition of a single sourceprecursor within a solid-state polymer showed promiseexcept that aggregates formed and reduced the effective poly-merNC interface area

Another approach to directly growing NCs involvedusing the polymer as a template for NC growth The qualityof the obtained NCs depended on the electrostatic and stericeffects imposed by this polymer [51] Cadmium acetate dihy-drate and P3HT were dissolved in mixed solvents containingdichlorobenzene (DCB) and dimethyl sulfoxide (DMSO)


(a) (b)

Figure 12 TEM images of the CdSP3HT composite layers (a) TEM image of the cross section of a 2 1 weight ratio CdSP3HT blend filmEDS was used to confirm the presence of Cd within region A whereas Cd was absent from region B (b) Top-down TEM image of a 2 1weight ratio CdSP3HT blend film Reprinted with permission from [69] Copyright 2010 ACS

Sulfur in DCB solution was then injected into the conjugatedpolymer and precursor solution at 180∘C for 30min to formCdS NCs in the P3HT matrix The purification of CdSpolymer composite was achieved by removing excess cad-mium sulfur ions and DMSO via adding anhydrous meth-anol to form the precipitate After centrifugation the super-natant was then removed and the composite redissolvedin DCB The solar cells with a device architecture of ITOPEDOTPSSP3HTCdSAl with an active layer preparedfollowing the redissolution composite solution In this ap-proach the CdS single crystal NRs having different aspectratios were easily obtained by controlling the cosolvent mix-ture ratio In fact the cosolvent ratio could be used to mod-ify the architecture of the polymer templates because thephysical conformations of the P3HT chains were affected bythe solvation propertiesThe planar P3HT conformation pro-vided a stacked molecular architecture (Figure 13(a)) TheCd2+ ions may have been confined within the networkthrough dipole-dipole or ion-dipole interactions between theCd2+ ions and the S atoms leading to the formation of uni-formly and randomly distributed CdS NCs and NRs withinthe P3HTmatrix At low concentrations of theCd2+ ions CdSNRs could not be formed (Figure 13(b)) although NR mor-phologies started to form at higher concentrations (Fig-ure 13(c)) ImprovedPLquenchingwas demonstrated forCdSNRs having a high aspect ratio as a result of the high interfacearea which formed pathways for electron transport A devicecomposed of P3HT and CdS NRs with an aspect ratio of 16showed a PCE of 29

First reports on the synthesis of PbS NCs in the solutioncontaining a conjugated polymer were from Watt et al in2004 [126] They describe the in situ preparation of PbS NCsin the presence of a conjugated polymer either MEH-PPV[126] or P3HT [127] by heating a solution of lead acetate ele-mental sulfur and the polymer in a solventmixture of DMSOand toluene to 160∘C for 15min Removing excess lead andsulfur ions by precipitation and redissolution followed bycoating on substrates completes the preparation of the nano-composite layers An advantage of this synthesis route is thatsize and shape of the NPs can be tuned quite easily A con-trolled formation of nanosized PbS particles in the presenceof the conjugated polymer was shown and attributed to steric

Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+

Figure 13 Schematic diagram showing the proposed CdSP3HTcomposite synthesis scheme The Cd2+ ions were assumed to becoupled to the unpaired S atoms along the P3HT planar chainnetwork Proposed mechanism for the growth of (b) CdS NCs and(d)NRs Reprintedwith permission from [51] Copyright 2009ACS

effects of the long polymer chains Without the polymerldquobulkrdquo PbSwas formed in the reaction solution FurthermoreStavrinadis et al [70] showed that nanorod-like structurescan be formed in aMeH-PPVmatrix by a post synthetic treat-ment (Figure 14) A precipitation of spherical PbS NPs inMEH-PPV solution using alcohol with the appropriate polar-ity like ethanol propanol or hexanol led to dipole-inducedoriented strings of PbSNPs although a precipitation inmeth-anol led to PbS nanocubes

The solar cell prepared PbS NPs exhibited a119881OC of 1 V an119869SC of 013 mAcmminus2 and a FF of 028 which leads to a PCE of07 under 5mWcmminus2 illumination [128] The moderate 119868SCand FF were ascribed to a high series resistance A possiblereason could have a relation large particle-particle distance ofthe PbS NPs

Unlike the nanocomposites crafted by ligand exchangeand direct grafting the NC size and shape the polymerNCsinterface and the dynamics of NC growth in the in situ-pre-pared hybrid materials were complex and the interactionsbetween the polymer and theNCs are poorly understoodThein situ approach has received significant attention due to itssimplicity and its potential for producing high-efficiency


20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)

Figure 14 TEM images of PbSMEH-PPV composites synthesis at 178∘C before precipitation (a) cubic colloidal particle formed afterprecipitation with methanol (b) rod structure after precipitation of the 175∘C composites with ethanol (c) 1-hexanol (d) The rectanglesemphasize areas with clearly distinguishable nanorods Many neighboring nanorods are aligned parallel to each other indicated by arrowsReprinted with permission from [70] Copyright 2008 Winley-VCH Verlag GmBH amp Co

hybrid solar cells however additional work may be requiredto optimize the in situ growth approach

4 Outlook and Conclusions

The polymer and inorganic components in hybrid photo-voltaic devices offer complementary advantages although thePCEs of these devices are currently low (sim38)The fabrica-tion of hybrid layers that yield both a high charge generationefficiency and a high charge collection efficiency faces severalchallenges The efficiency of charge generation may be im-proved by improving the extent of mixing between the donorand acceptor semiconductors by providing efficient excitondissociation at the donoracceptor interface The controllednanoscale morphology of the hybrid layer is required for theformation of an interpenetrating network for efficient chargetransportThis review discusses three strategies for preparingHPVs ligand exchange grafting and direct NC growthThese approaches are widely used to improve the compatibil-ity of polymers and inorganic NCs of various types and di-mensions in an effort to improve the photovoltaic perfor-mances of hybrid solar cells

Modifying the surfaces of NCs or polymers is a commonapproach to improving the quality of the hybrid active layerin an HPVThemodifier group can help passivate the surfacecharge traps suppress aggregation of the NCs in the polymermatrix and tune the energy level offset between the semicon-ductor and organic layer Nevertheless most ligands form an

insulating barrier that prevents charge transfer between thepolymers and the NCs and prevents electron transport bet-ween adjacent NCs The properties of the NC surface ligandsare the principle factors limiting the efficiencies of these lay-ers The ligands must be removed or exchanged with moreefficient surface modification molecules to improve phaseseparation facilitate charge transfer and hinder back recom-bination Ligand exchange effects are not yet well understoodand precise control over certain factors such as the exchangerate has proven to be difficult For the time being the use ofldquosmallrdquomolecules that reduce the interface surface energy hasbeen used to replace the original ligands containing long in-sulating alkyl chains The small molecules improve the effi-ciency of charge transfer and charge transport For exampleZnO-modified fullerene carboxylic acid (PCBA) has beentested [108 110] Modifications to the ZnO NP surfaces in-crease the device performance from 059 to 120 Elec-tronic coupling between the ZnO and C

60derivatives in-

creased 119869SC to 539mAcmminus2 by enhancing charge separationand improving the compatibility of the materials at theinterface

Grafting strategies are promising because they offer a highgrafting density that increases charge separation The devel-opment of controlled surface grafting processes is still neededto avoid excessive grafting which reduces the efficiency ofelectron transport between adjacent NCs Although muchwork can be done to optimize this approach controlling thegrafting density and the location is complicated The useof polymerinorganic nanocomposites blended with carbon


nanotubes (CNTs) [129ndash131] or graphene [132 133] has beenextremely attractive for improving the PCEs of HPVs Semi-conducting CNTs have a high absorbance in the visible andnear infrared (NIR) region and a high charge mobility (upto 105 cm2Vminus1sminus1 in individual nanotubes [94]) CNTs dopedor functionalized can formnano-assemblies with othermole-cules and polymers to provide the efficient photoinducedcharge transfer or to tune the Fermi levels and to improve thepositioning of the CNTs in the heterojunction region near thesemiconductor [71] In the recent study Derbal-Habak et al[134] demonstrated that the incorporation of 02 of func-tionalized SWCNTs into P3HTPCBM conventional OPVimproves the PCE of sim37 Fortunately Wang et al [135]created a P3HT-PbS QDs-MWCNT nanohybrid This deviceexhibited a large enhanced conversion efficiency of 303 ascompared with 257 for standard P3HTPCBM OPV Thecritical role of semiconducting CNTs may improve chargetransport by forming continuous pathways directly from theNCs to the electrodes that avoid the inefficient hopping path-ways along the NC networks Interestingly a high PCE ofsim14 in CNT Si hybrid solar cells has been reported [136]These results suggest that flexible solar cells may potentiallybe prepared by replacing p-type Si wafers with amorphous Sithin films

Finally the direct in situ growth of NCs in a polymermatrix offers an interesting approach to obtaining blendsof NCs and conjugated polymers due to its simplicity andrecent advances in NC synthesis This strategy still facesseveral challenges The NP size shape and distributionwithin the polymer matrix significantly influence the dielec-tric electronic optical and structural properties of thecomposite layer and the quality of NCs synthesized insitu has been rather low This problem can be resolved bycontrolling the growth of NCs within the polymer matrixA template approach employing diblock copolymers hasbeen considered as a means for guiding the growth of NCs[137ndash139] Rod-like ZnO NCs composed of ZnO NPs havebeen formed through templated self-assembly using a poly(3-hexylthiophene)-b-pol(zinc methacrylate acetate) (P3HT-b-PZnMAAc) diblock copolymer containing rigid thiophenechains and flexible chains [139] The dipole-induced inter-actions between adjacent ZnO NPs promoted the assemblyof rod-like ZnO NCs from ZnO NPs by aligning the crystalorientations and forming an interpenetrating network thatoffered efficient charge separation and transport Rod-likeZnO NCs were homogeneously dispersed in the polymermatrix without the need for a surfactant and the lengthsof the rod-like ZnO NCs could be controlled by adjustingthe hydrolysis time The PCEs of the P3HTZnO compositedevices were 019 although the weight fraction of ZnO wasvery low (10) A polymer having both electron acceptingand electron donating building blocks has been used for thepurpose of controlling the morphology in an HPV A hybridsolar cell prepared using a liquid crystal donoracceptorcopolymer poly[3-(6-(cyanobiphenyoxy)thiophene)-alt-47-(benzothiadiazole) (P3HbpT-BTD) and ZnO NPs yielded aPCE as high as 198 [138]

Hybrid solar cells are still lagging behind PCBM-basedOPV technologies with respect to device performance and

commercial applicability HPVs are currently under develop-ment and evaluation at the basic research level and they havethe potential to undergo further significant improvementsNovel device structures the implementation of nanostructur-ing methods and the development of low bandgap materialswill probably lead to PCE values on the order of 10 Progresstoward the development of organic-inorganic hybrid materi-als will benefit the development of hybrid solar cells as well asa variety of other applications such as light emitting diodesphotodiodes photodetectors fuel cells catalysts and sensors

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This research was supported by the Mid-career ResearcherProgram and Global Research Laboratory Program throughthe National Research Foundation of Korea funded by theMinistry of Science ICT amp Future Planning (No 2010-0029244)

References

[1] B R Saunders ldquoHybrid polymernanoparticle solar cells pre-paration principles and challengesrdquo Journal of Colloid andInterface Science vol 369 no 1 pp 1ndash15 2012

[2] B R Saunders andM L Turner ldquoNanoparticle-polymer photo-voltaic cellsrdquo Advances in Colloid and Interface Science vol 138no 1 pp 1ndash23 2008

[3] T Xu and Q Qiao ldquoConjugated polymer-inorganic semicon-ductor hybrid solar cellsrdquo Energy and Environmental Sciencevol 4 no 8 pp 2700ndash2720 2011

[4] L Zhao and Z Lin ldquoCrafting semiconductor organic-inorganicnanocomposites via placing conjugated polymers in intimatecontact with nanocrystals for hybrid solar cellsrdquoAdvancedMat-erials vol 24 pp 4353ndash4368 2012

[5] A J Moule L Chang C Thambidurai R Vidu and P StroeveldquoHybrid solar cells basic principles and the role of ligandsrdquo Jour-nal of Materials Chemistry vol 22 no 6 pp 2351ndash2368 2012

[6] R Zhou and J Xue ldquoHybrid polymer-nanocrystal materials forphotovoltaic applicationsrdquo Chemphyschem vol 13 pp 2471ndash2480 2012

[7] S A Gevorgyan A J Medford E Bundgaard et al ldquoAn inter-laboratory stability study of roll-to-roll coated flexible polymersolar modulesrdquo Solar Energy Materials and Solar Cells vol 95no 5 pp 1398ndash1416 2011

[8] F C Krebs T D Nielsen J Fyenbo M Wadstroslashm and M SPedersen ldquoManufacture integration and demonstration of pol-ymer solar cells in a lamp for the ldquolighting Africardquo initiativerdquoEnergy and Environmental Science vol 3 no 5 pp 512ndash5252010

[9] F Tong K Kim D Martinez et al ldquoFlexible organicinorganichybrid solar cells based on conjugated polymer and ZnO nano-rod arrayrdquo Semiconductor Science and Technology vol 27 Arti-cle ID 105005 2012


[10] C B Murray D J Norris and M G Bawendi ldquoSynthesis andcharacterization of nearlymonodisperseCdE (E S Se Te) semi-conductor nanocrystallitesrdquo Journal of the American ChemicalSociety vol 115 no 19 pp 8706ndash8715 1993

[11] T Ling M Wu and X Du ldquoTemplate synthesis and photovol-taic application of CdS nanotube arraysrdquo Semiconductor Scienceand Technology vol 27 Article ID 055017 2012

[12] J Boucle P Ravirajan and J Nelson ldquoHybrid polymer-metaloxide thin films for photovoltaic applicationsrdquo Journal of Mate-rials Chemistry vol 17 no 30 pp 3141ndash3153 2007

[13] S Dayal N Kopidakis D C Olson D S Ginley and G Rum-bles ldquoPhotovoltaic devices with a low band gap polymer andCdSe nanostructures exceeding 3 efficiencyrdquo Nano Lettersvol 10 no 1 pp 239ndash242 2010

[14] H Hoppe and N S Sariciftci ldquoMorphology of polymerfulle-rene bulk heterojunction solar cellsrdquo Journal ofMaterials Chem-istry vol 16 no 1 pp 45ndash61 2006

[15] M Pientka V Dyakonov D Meissner et al ldquoPhotoinducedcharge transfer in composites of conjugated polymers and semi-conductor nanocrystalsrdquoNanotechnology vol 15 no 1 pp 163ndash170 2004

[16] E Martınez-Ferrero J Albero and E Palomares ldquoMaterialsnanomorphology and interfacial charge transfer reactions inquantum dotpolymer solar cell devicesrdquo Journal of PhysicalChemistry Letters vol 1 no 20 pp 3039ndash3045 2010

[17] M D Heinemann K Von Maydell F Zutz et al ldquoPhoto-induced charge transfer and relaxation of persistent charge car-riers in polymernanocrystal composites for applications in hy-brid solar cellsrdquo Advanced Functional Materials vol 19 no 23pp 3788ndash3795 2009

[18] KMNoone S SubramaniyanQ Zhang G Cao S A Jenekheand D S Ginger ldquoPhotoinduced charge transfer and polarondynamics in polymer and hybrid photovoltaic thin filmsorganic vs inorganic acceptorsrdquo Journal of Physical Chemistry Cvol 115 no 49 pp 24403ndash24410 2011

[19] D S Ginger and N C Greenham ldquoCharge injection and trans-port in films of CdSe nanocrystalsrdquo Journal of Applied Physicsvol 87 no 3 pp 1361ndash1368 2000

[20] K F Jeltsch M Schadel J-B Bonekamp et al ldquoEfficiency en-hanced hybrid solar cells using a blend of quantum dots andnanorodsrdquo Advanced Functional Materials vol 22 no 2 pp397ndash404 2012

[21] K Kumari S Chand V D Vankar and V Kumar ldquoEnhance-ment in hole current density on polarization in poly(3- hexylth-iophene)cadmium selenide quantum dot nanocomposite thinfilmsrdquo Applied Physics Letters vol 94 no 21 Article ID 2135032009

[22] P Reiss E Couderc J De Girolamo and A Pron ldquoConjugatedpolymerssemiconductor nanocrystals hybrid materialsmdashpre-paration electrical transport properties and applicationsrdquoNanoscale vol 3 no 2 pp 446ndash489 2011

[23] S R Ferreira R J Davis Y-J Lee P Lu and JW P Hsu ldquoEffectof device architecture on hybrid zinc oxide nanoparticlepoly(3-hexylthiophene) blend solar cell performance and stabilityrdquoOrganic Electronics vol 12 no 7 pp 1258ndash1263 2011

[24] O Stenzel L J A Koster RThiedmann S D Oosterhout R AJ Janssen and V Schmidt ldquoA new approach to model-basedsimulation of disordered polymer blend solar cellsrdquo AdvancedFunctional Materials vol 22 no 6 pp 1236ndash1244 2012

[25] H E Unalan P Hiralal D Kuo B Parekh G Amaratunga andM Chhowalla ldquoFlexible organic photovoltaics from zinc oxide

nanowires grown on transparent and conducting single walledcarbonnanotube thin filmsrdquo Journal ofMaterials Chemistry vol18 no 48 pp 5909ndash5912 2008

[26] Y-CHuangW-C Yen Y-C Liao et al ldquoBand gap aligned con-ducting interface modifier enhances the performance of ther-mal stable polymer- TiO

2nanorod solar cellrdquo Applied Physics

Letters vol 96 no 12 Article ID 123501 2010[27] S Lu S-S Sun X Jiang J Mao T Li and K Wan ldquoIn situ 3-

hexylthiophene polymerization onto surface of TiO2based hy-

brid solar cellsrdquo Journal of Materials Science vol 21 no 7 pp682ndash686 2010

[28] M-CWuH-C LiaoH-H Lo et al ldquoNanostructured polymerblends (P3HTPMMA) inorganic titania hybrid photovoltaicdevicesrdquo Solar Energy Materials and Solar Cells vol 93 no 6-7pp 961ndash965 2009

[29] M Bredol K Matras A Szatkowski J Sanetra and A Prodi-Schwab ldquoP3HTZnS a new hybrid bulk heterojunction photo-voltaic systemwith very high open circuit voltagerdquo Solar EnergyMaterials and Solar Cells vol 93 no 5 pp 662ndash666 2009

[30] E Maier A Fischereder W Haas et al ldquoMetal sulfide-polymernanocomposite thin films prepared by a direct formation routefor photovoltaic applicationsrdquo Thin Solid Films vol 519 no 13pp 4201ndash4206 2011

[31] D Yun W Feng H Wu and K Yoshino ldquoEfficient conjugatedpolymer-ZnSe and -PbSe nanocrystals hybrid photovoltaic cellsthrough full solar spectrum utilizationrdquo Solar Energy Materialsand Solar Cells vol 93 no 8 pp 1208ndash1213 2009

[32] Y Kang N-G Park and D Kim ldquoHybrid solar cells with ver-tically aligned CdTe nanorods and a conjugated polymerrdquoApplied Physics Letters vol 86 no 11 Article ID 113101 pp 1ndash32005

[33] D Verma A Ranga Rao and V Dutta ldquoSurfactant-free CdTenanoparticles mixed MEH-PPV hybrid solar cell deposited byspin coating techniquerdquo Solar Energy Materials and Solar Cellsvol 93 no 9 pp 1482ndash1487 2009

[34] H C Chen C W Lai I C Wu et al ldquoEnhanced performanceand air stability of 32 hybrid solar cells how the functionalpolymer andCdTe nanostructure boost the solar cell efficiencyrdquoAdvanced Materials vol 23 pp 5451ndash5455 2011

[35] H-C Liao N Chantarat S-Y Chen and C-H Peng ldquoAnneal-ing effect on photovoltaic performance of hybrid P3HTIn-situgrown CdS nanocrystal solar cellsrdquo Journal of the Electrochemi-cal Society vol 158 no 7 pp E67ndashE72 2011

[36] L X Reynolds T Lutz S Dowland A MacLachlan S Kingand S A Haque ldquoCharge photogeneration in hybrid solar cellsa comparison between quantum dots and in situ grown CdSrdquoNanoscale vol 4 pp 1561ndash1564 2012

[37] V Resta AM Laera E Piscopiello M Schioppa and L TapferldquoHighly efficient precursors for direct synthesis of tailored CdSnanocrystals in organic polymersrdquo Journal of Physical ChemistryC vol 114 no 41 pp 17311ndash17317 2010

[38] H Bi and R R LaPierre ldquoA GaAs nanowireP3HT hybrid pho-tovoltaic devicerdquo Nanotechnology vol 20 no 46 Article ID465205 2009

[39] S Ren N Zhao S C Crawford M Tambe V Bulovic andS Gradecak ldquoHeterojunction photovoltaics using GaAs nano-wires and conjugated polymersrdquo Nano Letters vol 11 no 2 pp408ndash413 2011

[40] C J Novotny E T Yu and P K L Yu ldquoInP nanowirepolymerhybrid photodioderdquo Nano Letters vol 8 no 3 pp 775ndash7792008


[41] D Cui J Xu T Zhu G Paradee S Ashok and M GerholdldquoHarvest of near infrared light in PbSe nanocrystal-polymer hy-brid photovoltaic cellsrdquo Applied Physics Letters vol 88 no 18Article ID 183111 2006

[42] J Seo M J Cho D Lee A N Cartwright and P N PrasadldquoEfficient heterojunction photovoltaic cell utilizing nanocom-posites of lead sulfide nanocrystals and a low-bandgap poly-merrdquo Advanced Materials vol 23 no 34 pp 3984ndash3988 2011

[43] J Seo S J Kim W J Kim et al ldquoEnhancement of the photo-voltaic performance in PbS nanocrystalP3HT hybrid compos-ite devices by post-treatment-driven ligand exchangerdquo Nan-otechnology vol 20 no 9 Article ID 095202 2009

[44] Z Wang S Qu X Zeng et al ldquoSynthesis of MDMO-PPVcapped PbS quantum dots and their application to solar cellsrdquoPolymer vol 49 no 21 pp 4647ndash4651 2008

[45] L He C Jiang H Wang D Lai and R Rusli ldquoSi nanowiresorganic semiconductor hybrid heterojunction solar cells toward10 efficiencyrdquo ACS Applied Materials and Interfaces vol 4 no3 pp 1704ndash1708 2012

[46] C -Y Liu Z C Holman and U R Kortshagen ldquoHybrid solarcells from P3HT and silicon nanocrystalsrdquo Nano Letters vol 9no 1 pp 449ndash452 2009

[47] N Radychev D Scheunemann M Kruszynska et al ldquoInvestig-ation of the morphology and electrical characteristics of hybridblends based on poly(3-hexylthiophene) and colloidal CuInS

2

nanocrystals of different shapesrdquoOrganic Electronics vol 13 pp3154ndash3164 2012

[48] E Maier T Rath W Haas et al ldquoCuInS2Poly(3-(ethyl-4-buta-

noate)thiophene) nanocomposite solar cells preparation by anin situ formation route performance and stability issuesrdquo SolarEnergy Materials and Solar Cells vol 95 no 5 pp 1354ndash13612011

[49] E Arici HHoppe F Schaffler DMeissnerMAMalik andNS Sariciftci ldquoMorphology effects in nanocrystalline CuInSe

2-

conjugated polymer hybrid systemsrdquo Applied Physics A vol 79no 1 pp 59ndash64 2004

[50] J Liu W Wang H Yu Z Wu J Peng and Y Cao ldquoSurface lig-and effects in MEH-PPVTiO

2hybrid solar cellsrdquo Solar Energy

Materials and Solar Cells vol 92 no 11 pp 1403ndash1409 2008[51] H-C Liao S-Y Chen and D-M Liu ldquoIn-situ growing CdS

single-crystal nanorods via P3HT polymer as a soft template forenhancing photovoltaic performancerdquoMacromolecules vol 42no 17 pp 6558ndash6563 2009

[52] S D Oosterhout MMWienk S S Van Bavel et al ldquoThe effectof three-dimensional morphology on the efficiency of hybridpolymer solar cellsrdquoNatureMaterials vol 8 no 10 pp 818ndash8242009

[53] Y Peng G Song X Hu et al ldquoIn situ synthesis of P3HT-cappedCdSe superstructures and their application in solar cellsrdquoNano-scale Research Letters vol 8 article 106 2013

[54] J Liu T Tanaka K Sivula A P Alivisatos and J M J FrechetldquoEmploying end-functional polythiophene to control the mor-phology of nanocrystalmdashpolymer composites in hybrid solarcellsrdquo Journal of the American Chemical Society vol 126 no 21pp 6550ndash6551 2004

[55] A L Briseno T W Holcombe A I Boukai et al ldquoOligo- andpolythiopheneZnO hybrid nanowire solar cellsrdquo Nano Lettersvol 10 no 1 pp 334ndash340 2010

[56] S Ren L-Y Chang S-K Lim et al ldquoInorganic-organic hybridsolar cell bridging quantum dots to conjugated polymer nano-wiresrdquo Nano Letters vol 11 no 9 pp 3998ndash4002 2011

[57] Y-Y Lin T-H Chu S-S Li et al ldquoInterfacial nanostructuringon the performance of polymerTiO

2nanorod bulk heterojunc-

tion solar cellsrdquo Journal of the American Chemical Society vol131 no 10 pp 3644ndash3649 2009

[58] P V Kamat ldquoQuantum dot solar cells Semiconductor nano-crystals as light harvestersrdquo Journal of Physical Chemistry C vol112 no 48 pp 18737ndash18753 2008

[59] A Haugeneder M Neges C Kallinger et al ldquoExciton diffusionand dissociation in conjugated polymerfullerene blends andheterostructuresrdquo Physical Review B vol 59 no 23 pp 15346ndash15351 1999

[60] J E Kroeze T J Savenije M J W Vermeulen and J MWarman ldquoContactless determination of the photoconductivityaction spectrum exciton diffusion length and charge separa-tion efficiency in polythiophene-sensitized TiO

2bilayersrdquo Jour-

nal of Physical Chemistry B vol 107 no 31 pp 7696ndash7705 2003[61] T J Savenije JMWarman andAGoossens ldquoVisible light sen-

sitisation of titanium dioxide using a phenylene vinylene poly-merrdquoChemical Physics Letters vol 287 no 1-2 pp 148ndash153 1998

[62] T Ameri G Dennler C Lungenschmied and C J BrabecldquoOrganic tandem solar cells a reviewrdquo Energy and Environmen-tal Science vol 2 no 4 pp 347ndash363 2009

[63] J D Olson G P Gray and S A Carter ldquoOptimizing hybridphotovoltaics through annealing and ligand choicerdquo SolarEnergy Materials and Solar Cells vol 93 no 4 pp 519ndash5232009

[64] Y Zhou F S Riehle Y Yuan et al ldquoImproved efficiency ofhybrid solar cells based on non-ligand-exchanged CdSe quan-tum dots and poly(3-hexylthiophene)rdquo Applied Physics Lettersvol 96 no 1 Article ID 013304 2010

[65] J SeoW J Kim S J Kim K-S Lee A N Cartwright and P NPrasad ldquoPolymer nanocomposite photovoltaics utilizing CdSenanocrystals capped with a thermally cleavable solubilizingligandrdquoApplied Physics Letters vol 94 no 13 Article ID 1333022009

[66] Q Zhang T P Russell and T Emrick ldquoSynthesis and charac-terization of CdSe nanorods functionalized with regioregularpoly(3-hexylthiophene)rdquo Chemistry of Materials vol 19 no 15pp 3712ndash3716 2007

[67] H Skaff K Sill and T Emrick ldquoQuantum dots tailored withpoly(para-phenylene vinylene)rdquo Journal of the American Chem-ical Society vol 126 no 36 pp 11322ndash11325 2004

[68] S D Oosterhout L J A Koster S S Van Bavel et al ldquoCon-trolling the morphology and efficiency of hybrid ZnO poly-thiophene solar cells via side chain functionalizationrdquoAdvancedEnergy Materials vol 1 no 1 pp 90ndash96 2011

[69] H C Leventis S P King A Sudlow M S Hill K C Molloyand S A Haque ldquoNanostructured hybrid polymer Inorganicsolar cell active layers formed by controllable in situ growth ofsemiconducting sulfide networksrdquo Nano Letters vol 10 no 4pp 1253ndash1258 2010

[70] A Stavrinadis R Beal J M Smith H E Assender and A A RWatt ldquoDirect formation of PbS nanorods in a conjugated poly-merrdquo Advanced Materials vol 20 no 16 pp 3105ndash3109 2008

[71] C Goh S R Scully and M D McGehee ldquoEffects of molecularinterfacemodification in hybrid organic-inorganic photovoltaiccellsrdquo Journal of Applied Physics vol 101 no 11 Article ID114503 2007

[72] C B Murray D J Norris and M G Bawendi ldquoSynthesis andcharacterization of nearly monodisperse CdE (E = S Se Te)semiconductor nanocrystallitesrdquo Journal of the AmericanChemical Society vol 115 no 19 pp 8706ndash8715 1993


[73] J Park J Joo G K Soon Y Jang and T Hyeon ldquoSynthesis ofmonodisperse spherical nanocrystalsrdquo Angewandte Chemievol 46 no 25 pp 4630ndash4660 2007

[74] C de Mello Donega P Liljeroth and D VanmaekelberghldquoPhysicochemical evaluation of the hot-injection method asynthesis route formonodisperse nanocrystalsrdquo Small vol 1 no12 pp 1152ndash1162 2005

[75] X Peng ldquoMechanisms for the shape-control and shape-evolu-tion of colloidal semiconductor nanocrystalsrdquo Advanced Mate-rials vol 15 no 5 pp 459ndash463 2003

[76] H AMacpherson and C R Stoldt ldquoIron pyrite nanocubes sizeand shape considerations for photovoltaic applicationrdquo ACSNano vol 6 pp 8940ndash8949 2012

[77] L-S Li and A P Alivisatos ldquoSemiconductor nanorod liquidcrystals and their assembly on a substraterdquoAdvanced Materialsvol 15 no 5 pp 408ndash411 2003

[78] K M Ryan A Mastroianni K A Stancil H Liu and A PAlivisatos ldquoElectric-field-assisted assembly of perpendicularlyoriented nanorod superlatticesrdquo Nano Letters vol 6 no 7 pp1479ndash1482 2006

[79] W U Huynh J J Dittmer W C Libby G L Whiting and A PAlivisatos ldquoControlling the morphology of nanocrystal-poly-mer composites for solar cellsrdquo Advanced Functional Materialsvol 13 no 1 pp 73ndash79 2003

[80] S Gunes N Marjanovic J M Nedeljkovic and N S SariciftcildquoPhotovoltaic characterization of hybrid solar cells using sur-face modified TiO

2nanoparticles and poly(3-hexyl)thiophenerdquo

Nanotechnology vol 19 no 42 Article ID 424009 2008[81] L Han D Qin X Jiang et al ldquoSynthesis of high quality zinc-

blende CdSe nanocrystals and their application in hybrid solarcellsrdquo Nanotechnology vol 17 no 18 pp 4736ndash4742 2006

[82] M-C Wu C-H Chang H-H Lo et al ldquoNanoscale morphol-ogy and performance of molecular-weight-dependent poly(3-hexylthiophene)TiO

2nanorod hybrid solar cellsrdquo Journal of

Materials Chemistry vol 18 no 34 pp 4097ndash4102 2008[83] B Sun and N C Greenham ldquoImproved efficiency of photovol-

taics based on CdSe nanorods and poly(3-hexylthiophene)nanofibersrdquo Physical Chemistry Chemical Physics vol 8 no 30pp 3557ndash3560 2006

[84] J E Brandenburg X JinMKruszynska et al ldquoInfluence of par-ticle size in hybrid solar cells composed of CdSe nanocrystalsand poly(3-hexylthiophene)rdquo Journal of Applied Physics vol 110no 6 Article ID 064509 2011

[85] Y Zhou Y Li H Zhong et al ldquoHybrid nanocrystalpolymersolar cells based on tetrapod-shaped CdSe

119909Te1minus119909

nanocrystalsrdquoNanotechnology vol 17 no 16 article no 008 pp 4041ndash40472006

[86] H Lee S KimW-S Chung K Kim andD Kim ldquoHybrid solarcells based on tetrapod nanocrystals the effects of compositionsand type II heterojunction on hybrid solar cell performancerdquoSolar Energy Materials and Solar Cells vol 95 no 2 pp 446ndash452 2011

[87] I Gur N A Fromer C-P Chen A G Kanaras and A P Ali-visatos ldquoHybrid solar cells with prescribed nanoscale mor-phologies based on hyperbranched semiconductor nanocrys-talsrdquo Nano Letters vol 7 no 2 pp 409ndash414 2007

[88] J Yang A Tang R Zhou and J Xue ldquoEffects of nanocrystalsize and device aging on performance of hybrid poly(3-hex-ylthiophene)CdSe nanocrystal solar cellsrdquo Solar Energy Mate-rials and Solar Cells vol 95 no 2 pp 476ndash482 2011

[89] S-J Ko H Choi W Lee et al ldquoHighly efficient plasmonicorganic optoelectronic devices based on a conducting polymerelectrode incorporated with silver nanoparticlesrdquo Energy ampEnvironmental Science vol 6 p 1949 2013

[90] R Rajesh T Ahuja and D Kumar ldquoRecent progress in the de-velopment of nano-structured conducting polymersnanocom-posites for sensor applicationsrdquo Sensors and Actuators B vol136 no 1 pp 275ndash286 2009

[91] N C Greenham X Peng and A P Alivisatos ldquoCharge sep-aration and transport in conjugated-polymersemiconductor-nanocrystal composites studied by photoluminescence quench-ing and photoconductivityrdquo Physical Review B vol 54 no 24pp 17628ndash17637 1996

[92] I Lokteva N Radychev F Witt H Borchert J Parisi and JKolny-Olesiak ldquoSurface treatment of cdse nanoparticles forapplication in hybrid solar cells the effect of multiple ligand ex-change with pyridinerdquo Journal of Physical Chemistry C vol 114no 29 pp 12784ndash12791 2010

[93] N Radychev I Lokteva F Witt J Kolny-Olesiak H Borchertand J Parisi ldquoPhysical origin of the impact of different nano-crystal surface modifications on the performance of CdSeP3HT hybrid solar cellsrdquo Journal of Physical Chemistry C vol115 no 29 pp 14111ndash14122 2011

[94] J F Lin G Y Tu C C Ho et al ldquoMolecular structure effectof pyridine-based surface ligand on the performance of P

3HT

TiO2hybrid solar cellrdquo ACS Appl Mater Interfaces vol 5 pp

1009ndash1016 2013[95] Y ZhaoGYuan P Roche andM Leclerc ldquoA calorimetric study

of the phase transitions in poly(3-hexylthiophene)rdquo Polymervol 36 no 11 pp 2211ndash2214 1995

[96] D S Ginger and N C Greenham ldquoPhotoinduced electrontransfer from conjugated polymers to CdSe nanocrystalsrdquo Phys-ical Review B vol 59 no 16 pp 10622ndash10629 1999

[97] D J Milliron A P Alivisatos C Pitois C Edder and J M JFrechet ldquoElectroactive surfactant designed to mediate electrontransfer between CdSe nanocrystals and organic semiconduc-torsrdquo Advanced Materials vol 15 no 1 pp 58ndash61 2003

[98] C-H Chang T-K Huang Y-T Lin et al ldquoImproved chargeseparation and transport efficiency in poly(3- hexylthiophene)-TiO2nanorod bulk heterojunction solar cellsrdquo Journal of Mate-

rials Chemistry vol 18 no 19 pp 2201ndash2207 2008[99] J Boucle S Chyla M S P Shaffer J R Durrant D D C

Bradley and J Nelson ldquoHybrid bulk heterojunction solar cellsbased on blends of TiO

2nanorods and P3HTrdquo Comptes Rendus

Physique vol 9 no 1 pp 110ndash118 2008[100] J Weickert F Auras T Bein and L Schmidt-Mende ldquoCharac-

terization of interfacial modifiers for hybrid solar cellsrdquo Journalof Physical Chemistry C vol 115 no 30 pp 15081ndash15088 2011

[101] W J E Beek M M Wienk and R A J Janssen ldquoEfficienthybrid solar cells from zinc oxide nanoparticles and a conju-gated polymerrdquo Advanced Materials vol 16 no 12 pp 1009ndash1013 2004

[102] W J E Beek M M Wienk and R A J Janssen ldquoHybrid solarcells from regioregular polythiophene and ZnO nanoparticlesrdquoAdvanced FunctionalMaterials vol 16 no 8 pp 1112ndash1116 2006

[103] P A C Quist W J E Beek M M Wienk R A J Janssen T JSavenije and L D A Siebbeles ldquoPhotogeneration and decay ofcharge carriers in hybrid bulk heterojunctions of ZnO nanopar-ticles and conjugated polymersrdquo Journal of Physical Chemistry Bvol 110 no 21 pp 10315ndash10321 2006

[104] I Park Y Lim S Noh et al ldquoEnhanced photovoltaic perfor-mance of ZnO nanoparticlepoly(phenylene vinylene) hybrid


photovoltaic cells by semiconducting surfactantrdquo Organic Elec-tronics vol 12 no 3 pp 424ndash428 2011

[105] H-P Fang I-H Chiang C-W Chu C-C Yang andH-C LinldquoApplications of novel dithienothiophene- and 27-carbazole-based conjugated polymers with surface-modified ZnO nano-particles for organic photovoltaic cellsrdquo Thin Solid Films vol519 no 15 pp 5212ndash5218 2011

[106] S Shao F Liu G Fang B Zhang Z Xie and L Wang ldquoEn-hanced performances of hybrid polymer solar cells with p-methoxybenzoic acid modified zinc oxide nanoparticles as anelectron acceptorrdquo Organic Electronics vol 12 no 4 pp 641ndash647 2011

[107] K Yuan F Li L Chen Y Li and Y Chen ldquoLiquid crystal helpsZnO nanoparticles self-assemble for performance improve-ment of hybrid solar cellsrdquo Journal of Physical Chemistry C vol116 no 10 pp 6332ndash6339 2012

[108] D I Son B W Kwon J D Yang D H Park B Angadi andWK Choi ldquoHigh efficiency ultraviolet photovoltaic cells based onZnO-C

60core-shell QDs with organic-inorganic multilayer

structurerdquo Journal ofMaterials Chemistry vol 22 no 3 pp 816ndash819 2012

[109] C-T Chen F-C Hsu S-W Kuan and Y-F Chen ldquoThe effect ofC60

on the ZnO-nanorod surface in organicinorganic hybridphotovoltaicsrdquo Solar Energy Materials and Solar Cells vol 95no 2 pp 740ndash744 2011

[110] K Yao L Chen Y Chen F Li and P Wang ldquoInterfacial nano-structuring of ZnO nanoparticles by fullerene surface function-alization for ldquoAnnealing-Freerdquo hybrid bulk heterojunction solarcellsrdquo Journal of Physical Chemistry C vol 116 no 5 pp 3486ndash3491 2012

[111] B Park J-H Lee M Chang and E Reichmanis ldquoExciton dis-sociation and charge transport properties at a modified donoracceptor interfacepoly(3-hexylthiophene)Thiol-ZnO bulk het-erojunction interfacesrdquo Journal of Physical Chemistry C vol 116no 6 pp 4252ndash4258 2012

[112] A J Said G Poize C Martini et al ldquoHybrid bulk heterojunc-tion solar cells based on P3HT and porphyrin-modified ZnOnanorodsrdquo Journal of Physical Chemistry C vol 114 no 25 pp11273ndash11278 2010

[113] S Zhang PW Cyr S A McDonald G Konstantatos and E HSargent ldquoEnhanced infrared photovoltaic efficiency in PbSnanocrystalsemiconducting polymer composites 600-foldincrease in maximum power output via control of the ligandbarrierrdquoApplied Physics Letters vol 87 no 23 Article ID 2331013 pages 2005

[114] K M Noone E Strein N C Anderson P-TWu S A Jenekheand D S Ginger ldquoBroadband absorbing bulk heterojunctionphotovoltaics using low-bandgap solution-processed quantumdotsrdquo Nano Letters vol 10 no 7 pp 2635ndash2639 2010


[116] W Ma S L Swisher T Ewers et al ldquoPhotovoltaic performanceof ultrasmall PbSe quantum dotsrdquo ACS Nano vol 5 no 10 pp8140ndash8147 2011

[117] A H Ip S MThon S Hoogland et al ldquoHybrid passivated col-loidal quantum dot solidsrdquo Nat Nano vol 7 pp 577ndash582 2012

[118] J Xu J Wang M Mitchell et al ldquoOrganic-inorganic nanocom-posites via directly grafting conjugated polymers onto quantumdotsrdquo Journal of the American Chemical Society vol 129 no 42pp 12828ndash12833 2007

[119] P A van Hal M M Wienk J M Kroon et al ldquoPhotoinducedelectron transfer and photovoltaic response of a MDMO-PPVTiO

2bulk-heterojunctionrdquoAdvancedMaterials vol 15 no

2 pp 118ndash121 2003[120] W J E Beek L H SlooffMMWienk JM Kroon and R A J

Janssen ldquoHybrid solar cells using a zinc oxide precursor and aconjugated polymerrdquoAdvanced FunctionalMaterials vol 15 no10 pp 1703ndash1707 2005

[121] D J D Moet L J A Koster B De Boer and P W M BlomldquoHybrid polymer solar cells from highly reactive diethylzincMDMO-PPV versus P3HTrdquo Chemistry of Materials vol 19 no24 pp 5856ndash5861 2007

[122] S Dayal N Kopidakis D C Olson D S Ginley and GRumbles ldquoDirect synthesis of CdSe nanoparticles in poly(3-hexylthiophene)rdquo Journal of the American Chemical Society vol131 no 49 pp 17726ndash17727 2009

[123] L H Slooff JM Kroon J LoosMM Koetse and J SweelssenldquoInfluence of the relative humidity on the performance of poly-merTiO

2photovoltaic cellsrdquo Advanced Functional Materials

vol 15 no 4 pp 689ndash694 2005[124] SDOosterhoutMMWienkMAl-HashimiMHeeney and

R A J Janssen ldquoHybrid polymer solar cells from zinc oxide andpoly(3-hexylselenophene)rdquo Journal of Physical Chemistry C vol115 no 38 pp 18901ndash18908 2011

[125] S Dowland T Lutz A Ward et al ldquoDirect growth of metalsulfide nanoparticle networks in solid-state polymer films forhybrid inorganic-organic solar cellsrdquo Advanced Materials vol23 no 24 pp 2739ndash2744 2011

[126] A Watt E Thomsen P Meredith and H Rubinsztein-DunlopldquoA new approach to the synthesis of conjugated polymer-nano-crystal composites for heterojunction optoelectronicsrdquo Chemi-cal Communications vol 10 no 20 pp 2334ndash2335 2004

[127] J H Warner and A A R Watt ldquoMonodisperse PbS nanocrys-tals synthesized in a conducting polymerrdquoMaterials Letters vol60 no 19 pp 2375ndash2378 2006

[128] A A R Watt D Blake J H Warner et al ldquoLead sulfide nano-crystal conducting polymer solar cellsrdquo Journal of Physics Dvol 38 no 12 pp 2006ndash2012 2005

[129] L Chen X Pan D Zheng et al ldquoHybrid solar cells based onP3HT and SiMWCNT nanocompositerdquo Nanotechnology vol21 no 34 Article ID 345201 2010

[130] J M Lee B H Kwon H I Park et al ldquoExciton dissociation andcharge-transport enhancement in organic solar cells with quan-tum-DotN-doped CNT hybrid nanomaterialsrdquo AdvancedMaterials vol 25 no 14 pp 2011ndash2017 2013

[131] T-H Kim S-J Yang andC-R Park ldquoCarbon nanomaterials inorganic photovoltaic cellsrdquo Carbon Letters vol 12 pp 194ndash2062011

[132] Q Zheng G Fang F Cheng et al ldquoHybrid graphenendashZnOnanocomposites as electron acceptor in polymer-based bulk-heterojunction organic photovoltaicsrdquo Journal of Physics D vol45 Article ID 455103 2012

[133] C X Guo H B Yang Z M Sheng Z S Lu Q L Song and CM Li ldquoLayered graphenequantum dots for photovoltaic dev-icesrdquo Angewandte Chemie vol 49 no 17 pp 3014ndash3017 2010

[134] H Derbal-Habak C Bergeret J Cousseau and J M NunzildquoImproving the current density Jsc of organic solar cells P3HTPCBM by structuring the photoactive layer with functionalizedSWCNTsrdquo Solar Energy Materials and Solar Cells vol 95 no 1pp S53ndashS56 2011


[135] D Wang J K Baral H Zhao et al ldquoControlled fabrication ofpbs quantum-dotcarbon-nanotube nanoarchitecture and itssignificant contribution to near-infrared photon-to-currentconversionrdquo Advanced Functional Materials vol 21 no 21 pp4010ndash4018 2011

[136] Y Jia A Cao X Bai et al ldquoAchieving high efficiency silicon-car-bon nanotube heterojunction solar cells by acid dopingrdquo NanoLetters vol 11 no 5 pp 1901ndash1905 2011

[137] F Li Y Shi K Yuan and Y Chen ldquoFine dispersion and self-assembly of ZnO nanoparticles driven by P3HT-b-PEO di-blocks for improvement of hybrid solar cells performancerdquoNewJournal of Chemistry vol 37 article 195 2013

[138] F LiWChen andYChen ldquoMesogen induced self-assembly forhybrid bulk heterojunction solar cells based on a liquid crystalD-A copolymer and ZnO nanocrystalsrdquo Journal of MaterialsChemistry vol 22 no 13 pp 6259ndash6266 2012

[139] K Yuan F Li Y Chen X Wang and L Chen ldquoIn situ growthnanocomposites composed of rodlike ZnO nanocrystalsarranged by nanoparticles in a self-assembling diblock copoly-mer for heterojunction optoelectronicsrdquo Journal of MaterialsChemistry vol 21 no 32 pp 11886ndash11894 2011

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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advances and progress toward device improvement An out-look is provided on the futurematerials and technologies thatare likely to guide the future directions of research

2 Hybrid Solar Cells

21 Definitions ldquoHybridrdquo refers to the association of at leasttwo components of distinctly different chemical natures themolecular-level distribution of which components areachieved either through simplemixing or through linking thecomponents together via specific interactions such as cova-lent coordination ionic or hydrogen bonds Each hybridcomponent possesses its chemical identity and can exist inde-pendently of the hybrid material [22]

A bulk heterojunction is by definition a homogeneousblend of a p-type and an N-type semiconductor (donoracceptor) Organic photovoltaic devices (OPVs) based onblends of conjugated polymers and fullerenes form interpen-etrating donoracceptor networks and have been used in pro-totype bulk heterojunction geometry applications Bulk het-erojunctions in polymer-inorganic hybrid solar cells may beformed by replacing the fullerenes which act as organicnanoparticles (NPs) with inorganic semiconductors as elec-tron acceptors for dispersal in the polymermatrix NCs basedon metal oxides (ZnO [23ndash25] TiO

2[26ndash28]) group IIndashVI

(ZnS [29 30] ZnSe [31] CdTe [32ndash34] CdS [35ndash37]) groupIIIndashV (GaAs [38 39] InP [40]) group IVndashVI (PbSe [41] PbS[42ndash44]) group IV (Si [45 46]) CuInS

2[47 48] CuInSe

2

[49] have been tested for their utility as electron acceptors

22 Device Structure and Working Principle NCspolymerbulk heterojunction hybrid solar cells usually have devicearchitecture similar to those of organic solar cells (Figure 1)Anodes are often prepared by depositing indium tin oxide(ITO) which is conductive and transparent and which dis-plays a highwork function onto a flexible plastic or glass sub-strateThe conducted polymer poly(34-alkenedioxythiophe-nes)poly(styrenesulfonate) (PEDOTPSS) provides an anodebuffermaterial that enables efficient hole extraction Photoac-tive layers may be prepared by spin-coating a NCpolymerblend solution onto an ITO substrate to form a thin film 100ndash200 nm thick A top metal electrode (eg Al Ag and Ca)is then vacuum-deposited onto the photoactive layer as thecathode

As with OPVs the conversion of light energy into elec-tricity takes place in fourmain steps photon absorption exci-ton diffusion charge transfer and charge carrier transportand collection (Figure 2) Both organic semiconductor mate-rials and inorganic NCs can absorb incident light and createbound electron-hole pairs called excitons The excitons dif-fuse to the DA interface and then dissociate into free-chargecarriers The excitons dissociate at the interface if the energylevels of the NCs and the polymer are properly aligned Thischarge transfer process is necessary for creating a free-chargercarrier After charge separation the electrons and holes aretransported to their respective electrodes through percolatingpathways The holes are transported through the conjugated

PEDOTPSSITO substrate

NCspolymer

Metal cathode

NCs

Polymer

+ minus

C6H13

S n

Figure 1 Schematic diagram showing the structure of a typicalNCpolymer hybrid solar cell

Polymer phase

NCs phaseh

minusminus

minus

1

2

34

4

+

+

+

Figure 2 Schematic diagram showing the photocurrent generationmechanism in a bulk heterojunction hybrid solar cell excitongeneration (1) exciton diffusion (2) charge transfer (3) chargecarrier transport and collection (4)

polymer and the electrons are transported through theinorganic semiconductor (Figure 2)

The mechanism can be broken down into a number ofsteps each of whichmay be characterized by an efficiency (120578)which is defined on a scale of 0 to 1 The successful operationof a photovoltaic device requires that most or all of the stepsare characterized by 120578 close to 1 The overall efficiency of theconversion of incident photons to current that is the externalquantum efficiency (EQE) can be written as

EQE (120582 119881) = 120578119860(120582) times 120578diff times 120578diss (119881) times 120578tr (119881) times 120578cc (119881)

(1)

where 120582 is the wavelength of the incident light and 119881 is thevoltage across the cell120578119860(120582) is the photon absorption yield Most polymers have

a bandgap larger than 2 eV which limits the light absorptionrange As such materials with a complementary absorptionspectrum in the near-infrared range [42] or ultraviolet range[57 58] could be conjugated to the inorganic NCs120578diff is the exciton diffusion yieldThe fraction of excitons

that reach the DA interface is determined by the exciton dif-fusion length and the location at which an exciton is createdwith respect to the nearest dissociation center The excitondiffusion length in both anOPVand anHPV is in the range of10ndash20 nm for a conjugated polymer [59ndash61]







PCE =119875119898


(2)




FF =119875119898

119869SC times 119881OC (3)




119864119892


Curr

ent d

ensit

y

Voltage

Dark

Under illumination

Pmax VOC

JSC







119887) [3] In a bulk









Ligandexchange 319





Ligandexchange 36





Ligandexchange 0157


Liu et al (2008)[50]



In situ growth 29


Liao et al(2009) [51]



In situ growth 2





In situ growth 132


Peng et al(2013) [53]


Table 1 Continued




Grafting 11


Liu et al (2004)[54]



Grafting 0036





Grafting 41


Ren et al (2011)[56]











101

100

10minus1

10minus2

10minus3

10minus4

10minus5


Voltage (V)

Curr

ent d

ensit

y (m



(a)

(b)

(c)

(d)

(e)

A cm

minus2)






Curr

ent d

ensit

y (m

Ac

m2)

6

3

0

minus3

minus60 200 400 600

Voltage (mV)

(d)

VOC = 623mV

JSC = 58mAcm2

FF = 056

Eff = 20

(c)

H

HHN

N

O

O

OAcid

salt+

H2N

(a) (b)

100nm 100nm

OHNH2

NH2

HDA ligand sphere

H2 QDΔ

QD

CH3(CH2)3CH2

CH3(CH2)3CH2


QDS

S SS

S

SS S

SS

SSS

NH2

NH2

NH2

NH2H2N

H2N

H2N

H2NHNHN

HN

H

HN N O

OO

O

OO

OO

O

O

SO

ONHSO

ONH

S

OO NH

Δ


(a)

100∘C (photo)

100∘C (dark)

200∘C (photo)

200∘C (dark)

Curr

ent d

ensit

y (m

Ac

m2)

Curr

ent d

ensit

y (m

Ac

m2)15

10

05

00

minus05

minus10

minus1500 02 04 06 08 10

Voltage (V)

00 02 04 06 08 10Voltage (V)

100

10minus1

10minus2

10minus3

(b)








S CNS CNSn

CNSS

H

C6H13

CH2NH2SS

C6H13

Hn n


(2) H2O


4 1)

SH Br

C6H13

n

1

2

3 4


(a)

100nm 100nm

(b)




















BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









PCE =119875119898


(2)




FF =119875119898

119869SC times 119881OC (3)




119864119892


Curr

ent d

ensit

y

Voltage

Dark

Under illumination

Pmax VOC

JSC







119887) [3] In a bulk









Ligandexchange 319





Ligandexchange 36





Ligandexchange 0157


Liu et al (2008)[50]



In situ growth 29


Liao et al(2009) [51]



In situ growth 2





In situ growth 132


Peng et al(2013) [53]


Table 1 Continued




Grafting 11


Liu et al (2004)[54]



Grafting 0036





Grafting 41


Ren et al (2011)[56]











101

100

10minus1

10minus2

10minus3

10minus4

10minus5


Voltage (V)

Curr

ent d

ensit

y (m



(a)

(b)

(c)

(d)

(e)

A cm

minus2)






Curr

ent d

ensit

y (m

Ac

m2)

6

3

0

minus3

minus60 200 400 600

Voltage (mV)

(d)

VOC = 623mV

JSC = 58mAcm2

FF = 056

Eff = 20

(c)

H

HHN

N

O

O

OAcid

salt+

H2N

(a) (b)

100nm 100nm

OHNH2

NH2

HDA ligand sphere

H2 QDΔ

QD

CH3(CH2)3CH2

CH3(CH2)3CH2


QDS

S SS

S

SS S

SS

SSS

NH2

NH2

NH2

NH2H2N

H2N

H2N

H2NHNHN

HN

H

HN N O

OO

O

OO

OO

O

O

SO

ONHSO

ONH

S

OO NH

Δ


(a)

100∘C (photo)

100∘C (dark)

200∘C (photo)

200∘C (dark)

Curr

ent d

ensit

y (m

Ac

m2)

Curr

ent d

ensit

y (m

Ac

m2)15

10

05

00

minus05

minus10

minus1500 02 04 06 08 10

Voltage (V)

00 02 04 06 08 10Voltage (V)

100

10minus1

10minus2

10minus3

(b)








S CNS CNSn

CNSS

H

C6H13

CH2NH2SS

C6H13

Hn n


(2) H2O


4 1)

SH Br

C6H13

n

1

2

3 4


(a)

100nm 100nm

(b)




















BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








Ligandexchange 319





Ligandexchange 36





Ligandexchange 0157


Liu et al (2008)[50]



In situ growth 29


Liao et al(2009) [51]



In situ growth 2





In situ growth 132


Peng et al(2013) [53]


Table 1 Continued




Grafting 11


Liu et al (2004)[54]



Grafting 0036





Grafting 41


Ren et al (2011)[56]











101

100

10minus1

10minus2

10minus3

10minus4

10minus5


Voltage (V)

Curr

ent d

ensit

y (m



(a)

(b)

(c)

(d)

(e)

A cm

minus2)






Curr

ent d

ensit

y (m

Ac

m2)

6

3

0

minus3

minus60 200 400 600

Voltage (mV)

(d)

VOC = 623mV

JSC = 58mAcm2

FF = 056

Eff = 20

(c)

H

HHN

N

O

O

OAcid

salt+

H2N

(a) (b)

100nm 100nm

OHNH2

NH2

HDA ligand sphere

H2 QDΔ

QD

CH3(CH2)3CH2

CH3(CH2)3CH2


QDS

S SS

S

SS S

SS

SSS

NH2

NH2

NH2

NH2H2N

H2N

H2N

H2NHNHN

HN

H

HN N O

OO

O

OO

OO

O

O

SO

ONHSO

ONH

S

OO NH

Δ


(a)

100∘C (photo)

100∘C (dark)

200∘C (photo)

200∘C (dark)

Curr

ent d

ensit

y (m

Ac

m2)

Curr

ent d

ensit

y (m

Ac

m2)15

10

05

00

minus05

minus10

minus1500 02 04 06 08 10

Voltage (V)

00 02 04 06 08 10Voltage (V)

100

10minus1

10minus2

10minus3

(b)








S CNS CNSn

CNSS

H

C6H13

CH2NH2SS

C6H13

Hn n


(2) H2O


4 1)

SH Br

C6H13

n

1

2

3 4


(a)

100nm 100nm

(b)




















BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Table 1 Continued




Grafting 11


Liu et al (2004)[54]



Grafting 0036





Grafting 41


Ren et al (2011)[56]











101

100

10minus1

10minus2

10minus3

10minus4

10minus5


Voltage (V)

Curr

ent d

ensit

y (m



(a)

(b)

(c)

(d)

(e)

A cm

minus2)






Curr

ent d

ensit

y (m

Ac

m2)

6

3

0

minus3

minus60 200 400 600

Voltage (mV)

(d)

VOC = 623mV

JSC = 58mAcm2

FF = 056

Eff = 20

(c)

H

HHN

N

O

O

OAcid

salt+

H2N

(a) (b)

100nm 100nm

OHNH2

NH2

HDA ligand sphere

H2 QDΔ

QD

CH3(CH2)3CH2

CH3(CH2)3CH2


QDS

S SS

S

SS S

SS

SSS

NH2

NH2

NH2

NH2H2N

H2N

H2N

H2NHNHN

HN

H

HN N O

OO

O

OO

OO

O

O

SO

ONHSO

ONH

S

OO NH

Δ


(a)

100∘C (photo)

100∘C (dark)

200∘C (photo)

200∘C (dark)

Curr

ent d

ensit

y (m

Ac

m2)

Curr

ent d

ensit

y (m

Ac

m2)15

10

05

00

minus05

minus10

minus1500 02 04 06 08 10

Voltage (V)

00 02 04 06 08 10Voltage (V)

100

10minus1

10minus2

10minus3

(b)








S CNS CNSn

CNSS

H

C6H13

CH2NH2SS

C6H13

Hn n


(2) H2O


4 1)

SH Br

C6H13

n

1

2

3 4


(a)

100nm 100nm

(b)




















BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








101

100

10minus1

10minus2

10minus3

10minus4

10minus5


Voltage (V)

Curr

ent d

ensit

y (m



(a)

(b)

(c)

(d)

(e)

A cm

minus2)






Curr

ent d

ensit

y (m

Ac

m2)

6

3

0

minus3

minus60 200 400 600

Voltage (mV)

(d)

VOC = 623mV

JSC = 58mAcm2

FF = 056

Eff = 20

(c)

H

HHN

N

O

O

OAcid

salt+

H2N

(a) (b)

100nm 100nm

OHNH2

NH2

HDA ligand sphere

H2 QDΔ

QD

CH3(CH2)3CH2

CH3(CH2)3CH2


QDS

S SS

S

SS S

SS

SSS

NH2

NH2

NH2

NH2H2N

H2N

H2N

H2NHNHN

HN

H

HN N O

OO

O

OO

OO

O

O

SO

ONHSO

ONH

S

OO NH

Δ


(a)

100∘C (photo)

100∘C (dark)

200∘C (photo)

200∘C (dark)

Curr

ent d

ensit

y (m

Ac

m2)

Curr

ent d

ensit

y (m

Ac

m2)15

10

05

00

minus05

minus10

minus1500 02 04 06 08 10

Voltage (V)

00 02 04 06 08 10Voltage (V)

100

10minus1

10minus2

10minus3

(b)








S CNS CNSn

CNSS

H

C6H13

CH2NH2SS

C6H13

Hn n


(2) H2O


4 1)

SH Br

C6H13

n

1

2

3 4


(a)

100nm 100nm

(b)




















BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Curr

ent d

ensit

y (m

Ac

m2)

6

3

0

minus3

minus60 200 400 600

Voltage (mV)

(d)

VOC = 623mV

JSC = 58mAcm2

FF = 056

Eff = 20

(c)

H

HHN

N

O

O

OAcid

salt+

H2N

(a) (b)

100nm 100nm

OHNH2

NH2

HDA ligand sphere

H2 QDΔ

QD

CH3(CH2)3CH2

CH3(CH2)3CH2


QDS

S SS

S

SS S

SS

SSS

NH2

NH2

NH2

NH2H2N

H2N

H2N

H2NHNHN

HN

H

HN N O

OO

O

OO

OO

O

O

SO

ONHSO

ONH

S

OO NH

Δ


(a)

100∘C (photo)

100∘C (dark)

200∘C (photo)

200∘C (dark)

Curr

ent d

ensit

y (m

Ac

m2)

Curr

ent d

ensit

y (m

Ac

m2)15

10

05

00

minus05

minus10

minus1500 02 04 06 08 10

Voltage (V)

00 02 04 06 08 10Voltage (V)

100

10minus1

10minus2

10minus3

(b)








S CNS CNSn

CNSS

H

C6H13

CH2NH2SS

C6H13

Hn n


(2) H2O


4 1)

SH Br

C6H13

n

1

2

3 4


(a)

100nm 100nm

(b)




















BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




S CNS CNSn

CNSS

H

C6H13

CH2NH2SS

C6H13

Hn n


(2) H2O


4 1)

SH Br

C6H13

n

1

2

3 4


(a)

100nm 100nm

(b)




















BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials














BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




BrP O

Br

Br

P

P

O

O

C8H17

C8H17

C8H17

C8H17

Br

Br

SH

C8H17

C8H17

Br SH

C8H17

C8H17

Br SH

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

C8H17

C8H17

BrHS

H S

C6H13

OPBr

OPBrO P Br

O P Br

CdSe nanorodsHS

ligands

N N

N N

N

N N


Ligand exchange

n



Br

Br

Br

Br Br

P

P

P P

P

OO

O O

O


Br

BrC8H17 C8H17

C8H17C8H17

Br

P

P

P

P

O

OO

O

C8H17

C8H17

C8H17

C8H17

Br

C8H17

C8H17

C8H17

C8H17

Br

PO

C8H17 C8H17

C8H17 C8H17

Br

C8H17C8H17

C8H17 C8H17

Br

C8H17

C8H17

C8H17

C8H17

n

n

n

n

n





(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(1) nBuLi toluene

(2)PO

OO

Cl

C6H5

nSH Br

P3HTcoreshell

ZnO

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

C6H5

C6H5

OO

OO

O

O

P

P

n

n

SH

SH

equivSelf-assemble

on ZnO NWs

C6H5

PnO

O

OSH

P3HT

(a)

PO

OO Cl

(2)SS

SS

H25C12

C12H25

PO

OO

SS S

S

H25C12

C12H25

QTcoreshell

ZnOPO

OHOH

SS S

S

H25C12

C12H25

Self-assemble

on ZnO NWs

(1) TMS-Br

(2) H2O

QT


(b)




2






2semi-





2upon undergoing



100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




100nm

(a)

100nm

(b)

200nm

(c)

100nm

(d)







2S COS C





(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)




Growing

S2+(b)

(c)

(a)

SS

SS

Cd2+ Cd2+

Cd2+ Cd2+






20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




20nm

(a)

50nm

(b)

40nm

(c)

40nm

(d)







60derivatives in-










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










Acknowledgments


References






















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials















































2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











2





2-

















































119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





















119909Te1minus119909











3HT




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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Review Article Nanocomposite-Based Bulk Heterojunction ...downloads.hindawi.com/journals/jnm/2014/243041.pdf · Review Article Nanocomposite-Based Bulk Heterojunction Hybrid ... nanoparticles