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Materials Science and Technology
Stephan Buecheler, Fan Fu, Thomas Feurer, Stefano Pisoni, Enrico Avancini, Romain Carron, Shiro Nishiwaki, Ayodhya N. Tiwari
Contact: [email protected] Direct: +4158 765 61 07
Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, Switzerland;
CIGS-based Tandem Solar Cells
IW-CIGSTech 7 June 23rd, 2016
Materials Science and Technology 2
Efficiency potential of Cu(In,Ga)Se2 thin film solar cells
Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Jsc[mA/cm2]
Voc[mV]
FF [%]
Eff [%]
Empa cell on PI 35.1 736 78.9 20.4SQ-limit (1.15 eV) 42.3 887 87 32.7Losses compared to SQ-limit -17% -17% -9.3%
Jsc by ~10% (38.5 mA/cm2)
Voc by ~9% (800 mV)
FF by ~3%(81%)
efficiency of 25% for CIGS solar cells is a realistic goal
Envisaged improvement for CIGS (maybe not all applicable on flexible substrate):
Development supported by HZ2020 project Sharc25 with 11 European partners
Materials Science and Technology
Polycrystalline thin film solar cells with efficiency >30%?
3Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
• Module efficiency is critical to reduce non-module costs
Source: “PV Status Report 2014”, A. Jager-Waldau, JRC ReportsA. Polman, H.A. Atwater, Nature Materials 11,174–177 (2012)
Tandem can help here
Thermodynamic losses in PV
Chalcogenide and Perovskite thin film solar cells are promising for tandem devices:• Tunable, low bandgap• Polycrystalline, thin film absorbers on
various substrates deposited in cost-effective manner
Price breakdown of residential PV system
Other costs
Engineering procurement &
construction
Balance of systems
Inverter
PV module
Materials Science and Technology
Tandem configurations
4Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
+ Less optical losses in transparent contacts+ Only one DC circuit- Current matching required for all incident
angels- Reduced energy yield due to different
temperature and spectral dependence
2-terminal (monolithic) tandem
4-terminal tandem
+ Both cells can operate in resp. MPP+ “simple” stacking possible - Additional optical losses in transparent
contacts- Two DC circuits
Materials Science and Technology
Overview – CIGS based tandem devices
5Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Top cell Bottom cell Tandem deviceTechn. Efficiency
[%]Techn. Efficiency
[%]Efficiency filtered [%]
Config
Tandem efficiency [%]
Efficiency gain [%]*
Reference
Cd(Hg)Te 1.9 CIS NA 1.2 2t 3.0 1.1** J. D. Meakin, et al., Solar Cells, vol. 16, pp. 447–455, Jan. 1986.
CdTe 13.8 CIS NA 1.5 4t 15.3 1.5** X. Wu, et al., Symposium F – Thin-Film Compound Semiconductor Photovoltaics, 2005, vol. 865, p. F114
AIGS 5.3 CIGS 14.3 3.2 2t 8.0 -6.3 T. Nakada et al., IEEE 4th World Conference on PV, vol 1, 400-403, 2006.
CGS 4.3 CIGS 17.1 4.3 2t 8.5 -8.6 M. Schmid et al., EPJ Photovoltaics, vol 1, 10601, 2010.
DSSC 7.6 CIGS 13.9 8.2 4t 15.8 1.9 P. Liska, et al., Applied Physics Letters, vol. 88, no. 20, p. 203103, May 2006.
DSSC 7.3 CIGS 6.1 NA 2t 13.0 5.7** S. H. Moon, et al., Sci. Rep., vol. 5, Mar. 2015.
DSSC 8.4 CIGS 11.6 NA 2t 12.2 0.6 S. Wenger, et al., Applied Physics Letters, vol. 94, no. 17, p. 173508, Apr. 2009.
a-Si 3.1 CIS NA 2.0 2t 5.8 2.7** B. E. McCandless et al., 20th IEEE PSC, 1988, pp. 381–384 vol.1.
* Efficiency gain compared to the sub cell with highest efficiency.** Real efficiency gain unknown since unfiltered efficiency of bottom cell not measured/published
Tandem efficiency mainly limited by low performance and/or transmission of top cell
List
not
exh
aust
ive
Materials Science and Technology
Theoretical efficiency limit for 2 junction tandem solar cells
6Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Calculated maximum efficiency in the detailed balance limit for AM1.5G incident light. No optical losses included!
2-terminal tandem 4-terminal tandem
EG of state-of-the-art CIGS43.6%
CIS - EG44.5%43.8%
42.2%
Pero
vski
tead
just
edE G
E Gof
stat
e-of
-the-
art
Pero
vski
te
EG of state-of-the-art CIGS41.4%
CIS - EG43.6%38.0%
29.8%
Pero
vski
tead
just
edE G
E Gof
stat
e-of
-the-
art
Pero
vski
te
W. Schockley and H. J. Queisser, ‘‘Detailed balanced limit of efficiency of p-n junction solar cells’’, J. Appl. Phys. 32, 510 (1961).
Materials Science and Technology
State-of-the-art perovskite solar cells
7Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
perovskite
Planar structure Mesoporous structure(FAPbI3)1-x(MAPbBr3)xMAPbI3
J. Huang et al., Adv. Mater. 26, 6503 (2014)J. Huang et al., Adv. Mater. 2016, DOI::10.1002/ADMA.201600969
= 20.3%N. Jeon et al., Nature Materials 13, 897–903 (2014)http://www.nrel.gov/ncpv/images/efficiency_chart.jpg
Csx(MA0.17FA0.83)(100−x)Pb(I0.83Br0.17)3
M. Saliba et al., Energy Environ. Sci. 2016, DOI: 10.1039/C5EE03874J
Jinsong Huang et al., Uni. Labraska Lincoln S. Seok et al., KRICT: = 22.1%M. Grätzel et al., EPFL: = 21.1%
Materials Science and Technology
Low-temperature NIR-transparent Planar Perovskite Solar Cells for Bifacial and Tandem Applications
8Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
● Combine the merits of both vapor and solution processes
● Vapor process: homogeneous, compact and thickless controllable layer
● Solution process: composition engineering,
● Explore solvent sensitive electron transporting layers and novel cell design
Hybrid thermal evaporation/spin coating approach
F. Fu et al., Nat. Commun. 2015, 10.1002/aenm.201301400
Materials Science and Technology
Suppressed J-V hysteresis with PCBM on glass substrate
9Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
0.0 0.2 0.4 0.6 0.8 1.0 1.2-25
-20
-15
-10
-5
0
5
10
15
20
FB-SC SC-FB dark
Applied bias (V)
Cur
rent
den
sity
(mA
/cm
2 )
0 10 20 30 40 50 600
2
4
6
8
10
12
14
16
Time (s)
Effic
ienc
y (%
)
= 15.6 %
AM1.5G, scan rate: 0.3 V/s, delay time:10 ms
FB-SC: 1.2V to -0.1VSC-FB: -0.1V to 1.2V
MPP tracker: perturb and observe
Voc(V)
Jsc(mA/cm2)
FF(%)
Eff. (%)
ƞMPP(%)
Area(cm2)
FB-SC 1.075 19.1 73.6 15.115.6 0.15
SC-FB 1.076 19.1 74.7 15.3
unpublished results
Materials Science and Technology
Semi-transparent planar perovskite solar cells
10Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Eg of perovskite
F. Fu et al., Nat. Commun. 2015, 10.1002/aenm.201301400
Materials Science and Technology 11Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Bifacial perovskite solar cells
bifacial mode
front back
Mpp tracker: perturb and observation
Cell area: 0.517 cm2
~14%
F. Fu et al., Nat. Commun. 2015, 10.1002/aenm.201301400
Materials Science and Technology
CI(G)S as bottom cell in tandem device
12Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Adjustment of PDT and CBD processes required for changed CGI and GGI
1% gain in efficiency thanks to higher Jsc, FF
Sample (best cell) CGI(±0.02) GGI(±0.02) Voc(mV) Jsc(mA·cm-2) FF(%) η (%)Reference 0.79 0.34 718 34.7 76.1 19
14% CGI increase 0.9 0.31 701 35.2 74.6 18.414% CGI increase (improved interface) 0.89 0.34 718 35.9 76.8 19.9
NIR response improved!
So far 0.7 mA/cm2 gain
CIS
Towards CIS higher degree of freedom for buffer and window layerE. Avancini et al., presented at E-MRS Spring Meeting 2016, May 2nd-6th, 2016, Lille, France
Materials Science and Technology
CI(G)S as bottom cell in tandem device - BSF
13Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
[Ga]/([Ga]+[In]) VOC (mV) JSC (mA/cm2) FF (%) Eff (%)
A 0.377 699 31.6 75.0 16.6
B 0.284 662 33.2 76.0 16.8
C 0.192 612 34.0 75.3 15.6
D 0.149 502 35.8 66.5 12.0
E 0.000 444 37.0 67.2 11.0
SIMS [Ga]/([Ga]+[In]) profile Associated quantum efficiencyVOC loss in relation to the optical BG
Decreasing GGI: VOC ↓ JSC ↑ FF ↓
T. F
eure
r et a
l., p
rese
nted
at E
U-P
VS
EC
201
5, H
ambu
rg, G
erm
any
Materials Science and Technology
CI(G)S as bottom cell in tandem device – front grading/In2S3
14Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
SIMS [Ga]/([Ga]+[In]) profile PV performance
In2S3
CdS
VOC can be improved with front grading up to a certain steepness without mayor JSC losses
Fill factor drops considerably for stronger front grading, diminishing the gains in VOC
In2S3 buffer allows a strong increase in VOC, but the observed FF losses and light soaking
behavior need to be addressed before it can be applied in devices.
T. Feurer et al., presented at E-MRS Spring Meeting 2016, May 2nd-6th, 2016, Lille, France
Materials Science and Technology
CI(G)S as bottom cell in tandem device – PDT/doping
15Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Additional 20 minutes annealing @ ~350°C under Se atmosphereCdS CBD, i-ZnO/AZO front-contact
GGI VOC (mV) JSC (mA/cm2) FF (%) Eff (%)
CIS 0.00 444 37.0 67.2 11.0
CIS w/ annealing 0.00 491 39.1 72.6 13.9
Post deposition treatment needs to be adjusted for Ga free CIS EQE shows weak near infrared response, indicating collection issues Combination of BSF, front grading and modified PDT required
T. Feurer et al., presented at E-MRS Spring Meeting 2016, May 2nd-6th, 2016, Lille, France
Materials Science and Technology 16Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Perovskite-CIGS tandem device in 4-terminal configuration
20.5% Perovskite-CIGS in 4-terminal tandem configuration
6.3%
14.2%18.3%
F. Fu et al., Nat. Commun. 2015, 10.1002/aenm.201301400
Materials Science and Technology
Perovskite-CIGS tandem solar cells: 4-terminal
17Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Sample GGI VOC JSC Fill factor Efficiency 4t-Efficiency Efficiency gain[-] [mV] [mA/cm2] [%] [%] [%] [%]
Perovskite top cell - 1115 19.2 75.3 16.1 - -
CIGS Masked0.35
723 35.6 76.2 19.622.1CIGS Filtered 665 12.1 74.2 6 2.5
CIGS Masked0.35
696 35.6 77.3 19.2CIGS Filtered 669 12.1 73.6 6 22.1 2.9
CIGS Masked0.37
705 35.1 77.1 19.1CIGS Filtered 673 11.6 74 5.8 21.9 2.8
CIS masked-
453 39.2 73.1 13CIS filtered 428 15.3 73.1 4.8 20.9 4.8 (7.9)
Unpublished results
Materials Science and Technology
Perovskite based tandem solar cells – efficiency gain
18Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Y. Liu et al., ACS Appl. Mater. Interfaces 8, 7070 (2016)C. Chen et al., Mater. Horiz. 2, 203 (2015)J. P. Mailoa et al., Appl. Phys. Lett. 106, 121105 (2015)
J. Werner et al., J. Phys. Chem. Lett. 7, 161 (2016)
P. Löper et al., Phys. Chem. Chem. Phys. 17, 1619 (2015)
C. Bailie et al., Energy Environ. Sci.8, 956 (2015)
∆ƞ = 2.9%
∆ƞ = 2%
Materials Science and Technology
Perovskite and CIGS devices are suitable partners for high efficiency tandem devices
Clear efficiency gain in tandem devices compared to sub cells already achieved
Low-temperature grown all-thin-film PV device in tandem configuration with efficiency >22% suitable for flexible substrate
sub-cell efficiency – band gap of top and bottom cell – transmission through top cell – recombination layer – NIR response in bottom cell – stability of top cell …
Conclusion and Outlook
19Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Materials Science and Technology
Outlook: flexible perovskite-CIGS tandem devices
20Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
Flexible thin-film tandem device to overcome Shockley-Queisser single junction limit.
Challenges?
• Low-temperature flexible top cell
• Highly efficient NIR-transparent flexible perovskite solar cell
3BO.7.2S. Pisoni3BO.7.2S. Pisoni
Materials Science and Technology
Outlook: flexible perovskite-CIGS tandem devices
21Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
VOC (V) JSC (mA/cm2) FF (%) ƞ (%) ƞMPP (%) Cell area (cm2)
CIGS 0.66 34.7 77.7 17.8 17.8 0.213
CIGS bottom cell 0.63 12.6 77.1 6.1 6.1 0.213
Perovskite top cell 1.07 14.7 62.2 9.8 9.9 0.28
Tandem: 16%; ∆ƞ = -1.8%
CIGSTandem
Perovskite top cell CIGS
bottom cell
3BO.7.2S. Pisoni3BO.7.2S. Pisoni
Materials Science and Technology
Thanks for your attention
22Laboratory for Thin Films and Photovoltaics / Buecheler / IW CIGSTech 7
AcknowledgementsThe Competence Center for Energy and Mobility in ETH Domain and Swiss Federal Office of Energy: CONNECT-PVThe Swiss National Science Foundation NRP70: PV-2050NanoTera and The Swiss Federal Office of Energy: SynergyNanoTera: Synergy-GatewayFlisom AG
ContactLaboratory for Thin Films and Photovoltaics
Empa - Swiss Federal Laboratories for Materials Science and Technology Überlandstrasse 129, 8600 Dübendorf, Switzerland
Email: [email protected]
Disclaimer:The opinions expressed and arguments employed herein do not necessarily reflect the official views of the Swiss Government