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Photovoltaics - Electricity from Sunlight UNSW
““The Future of ThinThe Future of Thin--film Solarfilm SolarCellsCells””
Martin A. GreenMartin A. GreenUniversity of New South WalesUniversity of New South Wales
SydneySydney
UNSW Photovoltaics Centre of Excellence - supported by the Australian Research Council
Photovoltaics - Electricity from Sunlight UNSW
Photovoltaics boomingPhotovoltaics booming20
00
2002
2004
2006
2008
2010
0
2
4
6
8
10
New
Cap
acity
, GW
Source: Photon International
ThinThin--filmfilm
BulkBulk
Photovoltaics - Electricity from Sunlight UNSW
First generation cellsFirst generation cells
p-type
n ++
p +
metal
150-200 µm2-3 m m
Larger Si wafer area than ICsLarger Si wafer area than ICs
IssuesIssues
. thinner cells. thinner cells
. simpler Si purification. simpler Si purification
. higher conversion efficiency. higher conversion efficiency
Photovoltaics - Electricity from Sunlight UNSW
Second Generation: thinSecond Generation: thin--filmfilm
AdvantagesAdvantages. low materials cost. low materials cost. large manufacturing unit. large manufacturing unit. fully integrated modules. fully integrated modules. aesthetics, ruggedness?. aesthetics, ruggedness?
ThinThin--film Technologiesfilm Technologies. . SiliconSilicon
. amorphous. amorphous
. microcrystalline. microcrystalline
. polycrystalline. polycrystalline. . ChalcogenideChalcogenide (polycrystalline)(polycrystalline)
. CIS, CIGS [Cu (. CIS, CIGS [Cu (In,GaIn,Ga) (Se,S)) (Se,S)22]]
. . CdTeCdTe. . Dye sensitisedDye sensitised, , OrganicsOrganics
Photovoltaics - Electricity from Sunlight UNSW
Silicon ThinSilicon Thin--FilmFilm
aa--Si, Si, µµcc--Si, cSi, c--SiSiamorphous, microcrystalline, (polyamorphous, microcrystalline, (poly--)crystalline)crystalline
Photovoltaics - Electricity from Sunlight UNSW
ChalcogenidesChalcogenides: CdTe and CIGS: CdTe and CIGS
. easily deposited . easily deposited
. Cd toxic, Te scarce. Cd toxic, Te scarce
. highest efficiency. highest efficiency
. tricky to deposit . tricky to deposit
. Cd toxic, In scarce. Cd toxic, In scarceCdTeCdTe
CIGSCIGS
glassTCO
windowalloy layer
absorbermetal contact
SnO2CdS
CdSxTe1-x
CdTe
contact Mo
TCOwindow
absorber
ZnO
glass
Cu (Ga,In) (Se,S)2
CdS
substrate
CuInGaSeSCuInGaSeS
Photovoltaics - Electricity from Sunlight UNSW
Other Advanced ThinOther Advanced Thin--Films:Films:DyeDye--sensitised; Organicsensitised; Organic
Photovoltaics - Electricity from Sunlight UNSW
Cost reductionCost reduction
20000
10000
5000
2000
1000
500
2000.01 0.1 1.0 10.0 100.0
Gas turbines (USA)(~20%, ~10%)
1980
1963
1982
19871993
2001
Wind turbines 2002
Cumulative GW installed
1981
Photovoltaics(learning ~20%)
USA (~20%)
World (~5%)
2003
US$
/kW
Adapted from Adapted from GrGrüüblerbler et al.,1999et al.,1999
Photovoltaics - Electricity from Sunlight UNSW
ThinThin--filmfilm
Cost reductionCost reduction
20000
10000
5000
2000
1000
500
2000.01 0.1 1.0 10.0 100.0
Gas turbines (USA)(~20%, ~10%)
1980
1963
1982
19871993
2001
Wind turbines 2002
Cumulative GW installed
1981
Photovoltaics(learning ~20%)
USA (~20%)
World (~5%)
2003
US$
/kW
““ThinThin--filmfilm”” PhotovoltaicsPhotovoltaics
Adapted from Adapted from GrGrüüblerbler et al.,1999et al.,1999
Photovoltaics - Electricity from Sunlight UNSW
The 3 generationsThe 3 generations
II
100
80
60
20
0 100 200 300 400 500
US$0.50/W
US$1.00/W
US$3.50/W
Cost, US$/m2
US$0.10/W US$0.20/W
Present limitIII
Thermodynamiclimit
40
I
Effic
ienc
y,%
BulkBulk
Photovoltaics - Electricity from Sunlight UNSW
The 3 generationsThe 3 generations
II
100
80
60
20
0 100 200 300 400 500
US$0.50/W
US$1.00/W
US$3.50/W
Cost, US$/m2
US$0.10/W US$0.20/W
Present limitIII
Thermodynamiclimit
40
I
Effic
ienc
y,%
Includes dye, organicIncludes dye, organic
ThinThin--filmfilm
Photovoltaics - Electricity from Sunlight UNSW
Thermodynamic efficiency limitsThermodynamic efficiency limits
Tc
EsSs
Ec
Sc
SG>0
TA
W
Q
S = Q/TA
η ≤ (1-TASs/Es) = 93.3% (direct) = 73.7% (global)
Photovoltaics - Electricity from Sunlight UNSW
The 3 generationsThe 3 generations
?
II
100
80
60
20
0 100 200 300 400 500
US$0.50/W
US$1.00/W
US$3.50/W
Cost, US$/m2
US$0.10/W US$0.20/W
Present limitIII
Thermodynamiclimit
40
I
Effic
ienc
y,%
. high. high--efficiencyefficiency
. thin. thin--filmfilm
. abundant. abundant
. non. non--toxictoxic
. durable. durable
Photovoltaics - Electricity from Sunlight UNSW
UNSW approachUNSW approach
II
Evolutionary emphasis Evolutionary emphasis upon crystalline siliconupon crystalline silicon
(robust, abundant, non(robust, abundant, non--toxic)toxic)
Photovoltaics - Electricity from Sunlight UNSW
UNSW approachUNSW approach
II
IIII
Evolutionary emphasis Evolutionary emphasis upon crystalline siliconupon crystalline silicon
(robust, abundant, non(robust, abundant, non--toxic)toxic)
Photovoltaics - Electricity from Sunlight UNSW
UNSW approachUNSW approach
?II
IIII
IIIIIIEvolutionary emphasis Evolutionary emphasis upon crystalline siliconupon crystalline silicon
(robust, abundant, non(robust, abundant, non--toxic)toxic)
Photovoltaics - Electricity from Sunlight UNSW
Third generation optionsThird generation options
100%
74%68%
54%49%44%39%31%
0%
58%
circulators
tandem (n )hot carrier
impurity PV & band, up-converterstandem (n = 3)thermal, thermoPV, thermionics
impact ionisationtandem (n = 2)down-converterssingle cell
tandem (n = 6)
Photovoltaics - Electricity from Sunlight UNSW
Third generation optionsThird generation options
100%
74%68%
54%49%44%39%31%
0%
58%
circulators
tandem (n )hot carrier
impurity PV & band, up-converterstandem (n = 3)thermal, thermoPV, thermionics
impact ionisationtandem (n = 2)down-converterssingle cell
tandem (n = 6)
Photovoltaics - Electricity from Sunlight UNSW
SiSi--based tandemsbased tandems
42.5%47.5%
50.5%
Number of cells1 2 3
10
20
30
40
00
Si bottom cellFree choice
29%
33%
45%
AM1.
5G E
ffici
ency
Free choiceor Si cell
Decreasing band gap
Sunlight
Intrinsic radiative and Auger losses includedIntrinsic radiative and Auger losses included
Photovoltaics - Electricity from Sunlight UNSW
SiSi--tandem concepttandem concept
CSG Solar approachCSG Solar approach. high. high--T siliconT silicon
. high. high--density contactsdensity contacts
. good optics. good optics
. deposit then process. deposit then process
. also suits hot. also suits hot--carriercarrier
MetalResinp+
n+
Light In
p+pn+
p
Textured glass'Crater' 'Groove' 'Dimple'
Up-converters ?
1 - 3 QD cells ?
Photovoltaics - Electricity from Sunlight UNSW100nm100nm
Fabrication of Si quantum dotsFabrication of Si quantum dots
SiOx, SiyNx, SiCxSiO2, Si3N4, SiC
Zacharias et al., APL Zacharias et al., APL 8080, 661, 2002, 661, 2002
Photovoltaics - Electricity from Sunlight UNSW
Si quantum dot photoluminescenceSi quantum dot photoluminescence
Norm. PL Spectra (2-5nm dots; 300K)
01.2 1.4 1.6 1.8 2
Photon energy, eV
5nm (270s)4nm (240s)3nm (180s)2nm (120s)
100nm100nm
Photovoltaics - Electricity from Sunlight UNSW
Third generation optionsThird generation options
100%
74%68%
54%49%44%39%31%
0%
58%
circulators
tandem (n )hot carrier
impurity PV & band, up-converterstandem (n = 3)thermal, thermoPV, thermionics
impact ionisationtandem (n = 2)down-converterssingle cell
tandem (n = 6)
Photovoltaics - Electricity from Sunlight UNSW
HotHot--carrier cell conceptcarrier cell concept
tunnelingcontact
absorber
100nm100nm
Bandgap (eV)
cold carriers
0.0 0.5 1.0 1.5 2.0 2.5 3.0
80
60
40
20
0
Effic
ienc
y (%
) 1
2hot carriers
InN Si
quantum dot absorber
hole contactelectron contact
TTaa
TTcc
Efficiency > 4 cell tandem
Photovoltaics - Electricity from Sunlight UNSW
SummarySummary
. . need to fix carbon problem at sourceneed to fix carbon problem at source–– provide clean, more costprovide clean, more cost--effective electricity optionseffective electricity options
. photovoltaics provides a solution provided. photovoltaics provides a solution provided–– volumes increased and costs reduced dramaticallyvolumes increased and costs reduced dramatically
. high energy conversion efficiency is the key to lowest . high energy conversion efficiency is the key to lowest possible longpossible long--term coststerm costs
. high efficiency thin. high efficiency thin--film technologies described forfilm technologies described forpostpost--2020 era2020 era
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