cigs-based tandem solar cells - eupvsec...materials science and technology 2 efficiency potential of...

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


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


Tandem configurations


+ 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


Overview – CIGS based tandem devices


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


Theoretical efficiency limit for 2 junction tandem solar cells


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).


State-of-the-art perovskite solar cells


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%


Low-temperature NIR-transparent Planar Perovskite Solar Cells for Bifacial and Tandem Applications


● 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


Suppressed J-V hysteresis with PCBM on glass substrate


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


Semi-transparent planar perovskite solar cells


Eg of perovskite


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%



CI(G)S as bottom cell in tandem device


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


CI(G)S as bottom cell in tandem device - BSF


[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


CI(G)S as bottom cell in tandem device – front grading/In2S3


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


CI(G)S as bottom cell in tandem device – PDT/doping


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%



Perovskite-CIGS tandem solar cells: 4-terminal


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


Perovskite based tandem solar cells – efficiency gain


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%


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



Outlook: flexible perovskite-CIGS tandem devices


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


Outlook: flexible perovskite-CIGS tandem devices


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


Thanks for your attention


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

cigs-based tandem solar cells - eupvsec...materials science and technology 2 efficiency potential of...

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