Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier
23 June 20167th International Workshop on CIGS Solar Cell Technology (IW-CIGSTech 7)32nd EU PVSEC, 20-24 June 2016ICM, Munich, Germany
Takuya KatoAtsugi Research CenterSolar Frontier K.K.
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 2
CIGS solar cell/module development in Solar Frontier
Small Cell~0.5cm2
Cd-free Submodule800 – 40cm2
Cd-freeProduction Module
~90×120cm2
~60×120cm2
MP1 (20MW)MP2 (60MW)
MP3 (900MW)MP4 (150MW)
22.3%(CdS)
22.0%(Cd-free)
18.6%(Cd-free)
22.7% in-house(CdS)
22.8% in-house(Cd-free)
(Aperture Area)
Atsugi Research CenterAtsugi Research Center
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 3
CIGS solar cell/module development in Solar Frontier
Small Cell~0.5cm2
Cd-free Submodule800 – 40cm2
Cd-freeProduction Module
~90×120cm2
~60×120cm2
MP1 (20MW)MP2 (60MW)
MP3 (900MW)MP4 (150MW)
22.3%(CdS)
22.0%(Cd-free)
18.6%(Cd-free)
22.7% in-house(CdS)
22.8% in-house(Cd-free)
(Aperture Area)
Atsugi Research CenterAtsugi Research Center
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 4
Solar Frontier’s CIGS technology
CIS-based absorberby selenization & sulfurization (SAS)
Patterning 1by laser scribing
Mo back electrodeby sputtering Metal precursor
by sputtering
ZnO windowby MOCVD
Zn(O,S,OH)x bufferby CBD
Patterning 2by mechanical scribing
Patterning 3by mechanical scribing
Fabrication ProcessGlass substrate
Mo back electrode
P1
Zn(O,S,OH)x buffer
CIS-based absorberS-rich front grading
Ga-rich back grading
ZnO window
Device Structure
P2 P3
S-rich
Ga-rich
EV
EC
Front Back
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 5
Solar Frontier as the world’s largest CIGS ManufacturerHQ: TokyoFactories: 3Research Center: 1
Miyazaki Factory (MP2)
Kunitomi Factory (MP3)
Atsugi Research Center(ARC) Tokyo HQ
Tohoku Factory (MP4)
Solar Frontier’s proprietary lines are fully automated, proven in mass production and producing modules at globally competitive cost levels
Tohoku Plant (MP4)Tohoku Plant (MP4)Kunitomi Plant (MP3)Kunitomi Plant (MP3)Miyazaki Plant (MP2)Miyazaki Plant (MP2)
Online: 2009 Online: 2011 Online: 2015
Location: Miyagi, Japan
Capacity: 150 MW
Location: Miyazaki, Japan
Capacity: 900 MW
Location: Miyazaki, Japan
Capacity: 60 MW
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 6
Tohoku Plant (MP4) with the latest CIGS technologyThe Tohoku Plant introduces Solar Frontier’s latest production technology, which serves as a blueprint for future factories
Faster production time
Compact design
Higher module efficiency %
2/3 OPEX/CAPEX per MW $
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 7
CIGS solar cell/module development in Solar Frontier
Small Cell~0.5cm2
Cd-free Submodule800 – 40cm2
Cd-freeProduction Module
~90×120cm2
~60×120cm2
MP1 (20MW)MP2 (60MW)
MP3 (900MW)MP4 (150MW)
22.3%(CdS)
22.0%(Cd-free)
18.6%(Cd-free)
22.7% in-house(CdS)
22.8% in-house(Cd-free)
(Aperture Area)
Atsugi Research CenterAtsugi Research Center
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 8
CIGS solar cell/module development in Solar Frontier
Small Cell~0.5cm2
Cd-free Submodule800 – 40cm2
Cd-freeProduction Module
~90×120cm2
~60×120cm2
MP1 (20MW)MP2 (60MW)
MP3 (900MW)MP4 (150MW)
22.3%(CdS)
22.0%(Cd-free)
18.6%(Cd-free)
22.7% in-house(CdS)
22.8% in-house(Cd-free)
(Aperture Area)
Atsugi Research CenterAtsugi Research Center
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 9
Improved Cd-free submodule efficiency: 18.6%
Mar. 201517.9%(□30cm)
Mar. 201618.6%(□7cm)
Date Area Cells η Jsc Voc FF Eg Voc,def Jsc/JscSQ
(cm2) (%) (mA/cm2) (mV) (%) (eV) (mV) (%)
2015.3 783 90 17.9 36.3 674 73.2 1.13 453 83.3
2016.3 39.6 14 18.6 35.7 703 74.0 1.16 458 85.2
Widened bandgap20.9% cell tech.・CIGS improvement・TCO improvement
Still rooms for improvements:・Dead area, cell pitch・22.8% cell tech.・etc…
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 10
CIGS solar cell/module development in Solar Frontier
Small Cell~0.5cm2
Cd-free Submodule800 – 40cm2
Cd-freeProduction Module
~90×120cm2
~60×120cm2
MP1 (20MW)MP2 (60MW)
MP3 (900MW)MP4 (150MW)
22.3%(CdS)
22.0%(Cd-free)
18.6%(Cd-free)
22.7% in-house(CdS)
22.8% in-house(Cd-free)
(Aperture Area)
Atsugi Research CenterAtsugi Research Center
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 11
CIGS solar cell/module development in Solar Frontier
Small Cell~0.5cm2
Cd-free Submodule800 – 40cm2
Cd-freeProduction Module
~90×120cm2
~60×120cm2
MP1 (20MW)MP2 (60MW)
MP3 (900MW)MP4 (150MW)
22.3%(CdS)
22.0%(Cd-free)
18.6%(Cd-free)
22.7% in-house(CdS)
22.8% in-house(Cd-free)
(Aperture Area)
Atsugi Research CenterAtsugi Research Center
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 12
Learnings from our previous record cell
0
0,2
0,4
0,6
0,8
1
300 500 700 900 1100 1300
EQE
Wavelength (nm)
0
10
20
30
40
0 200 400 600 800
Cur
rent
Den
sity
(mA/
cm2 )
Voltage (mV)
2012 2014η (%) 19.7 20.9
Voc (mV) 683 686Jsc (mA/cm2) 37.1 39.9
FF (%) 77.8 76.5
What we did from 19.7% to 20.9%: focused on Jsc improvement• Light absorber band profile optimization• ZnO:B window layer optimization
What we should do next for pushing efficiency limits;• Reduce space charge region recombination rate for higher Voc
2012
2014
M. Nakamura et al., 40th IEEE PVSC (2014)
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 13
Loss analysis on 19.7% cell
H. Sugimoto et al., 40th IEEE PVSC (2014), revised
Glass substrateControl layer
Back electrode(Mo(S,Se)2/Mo)
p-type absorber layer (CIGSSe)
n-type buffer layer (CBD-Zn(O,S,OH)x)
Nondoped layer (MOCVD-ZnO)
TCO layer (MOCVD-ZnO:B)
Grid electrode (Al)
Anti-reflection layer (MgF2)
Jsc improvement has been done. Much room for improvement in Voc.
Opt
ical
Elec
tric
al19.7%eff
(60.9%SQ)
683mV(81.6%SQ)
37.1mA/cm2
(83.2%SQ)
77.8%(89.8%SQ)
GaAs
c-Si
SF-CIGS
LossAchievements
Device & Material Analysis
Optical & Device Simulations
Efficiency Loss Analysis
20.9%eff
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 14
Recombination analysis on 20.9% cell
0,5
0,7
0,9
1,1
0 100 200 300 400
V oc
at 1
sun
(V)
T (K)
0,3
0,5
0,7
0,01 0,1 1 10
V oc
at 2
98 K
(V)
G (Sun)
R0i
(cm-2 s-1)R0
d
(cm-2 s-1)R0
b
(cm-2 s-1)Ri
(cm-2 s-1)Rd
(cm-2 s-1)Rb
(cm-2 s-1)
SF-20.9% 6.3×103 2.0×1011 7.4×105 1.9×1015 1.1×1017 2.3×1017
Ref. [1] 6.4×104 3.3×1010 3.4×105 1.4×1016 2.2×1016 1.4×1017
[1] J. Li,et.al., Solar Energy Materials & Solar Cells, 124, 143 (2014).
Recombination at the interface (Ri) & in the bulk (Rb) is not bad. Recombination in the space charge region (Rd) is definitely worse;
• CIGS surface passivation by K-treatment• 2nd buffer layer (nondoped layer) optimization
EA = 1.048 eV
Suns-Voc Voc-T
R0x: V-independent coefficients
M. Nakamura et al., 42nd IEEE PVSC (2015)
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 15
K-treatment for CIGSSe formed by selenization & sulfurization
KF deposition amount (a.u.)
N/A 1 5 50 250
Annealing temperature (°C)
N/A
100
150
250
SAS processedCIGSSe
K-treatment
K sourcematerial
depositionmethod
Kamount
Annealingcondition
example: KF evaporation optimum combination
K-sourceDeposition
Annealing
K-treatment works for CIGS that• contains sulfur• formed by two-step process(sputter deposition of metal precursorfollowed by selenization and sulfurization)
Voc: +30mV
R. Kamada et al., 43rd IEEE PVSC (2016)
V OC
(mV)
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 16
(Zn,Mg)O for the second buffer layer (nondoped layer)
first buffer layer
second buffer layer
ZnO ZnMgO ZnO ZnMgO
Zn(O,S,OH) CdS
2nd buffer layer: ALD-deposited (Zn,Mg)O
first buffer layer
3
4
5
0 0,2 0,4 0,6
E g(e
V)
[Mg]/([Zn]+[Mg])
tunable Eg
ALD-(Zn,Mg)O
ALD-(Zn,Mg)O for the second buffer layer• increases Jsc due to wide Eg• improves Voc in Cd-free buffer
R. Kamada et al., 43rd IEEE PVSC (2016)
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 17
Voc enhancement due to reduction of recombination rate
Cd-free!
K-PDT
Zn(O,S,OH)
(Zn,Mg)O
CdS
ZnO
N/A
2nd buffer:
1st buffer:
K-treatment:
VOC (mV)
Eg/q - VOC (mV)
Rd0 (cm-2 s-1)
SF-20.9%SF-20.9%
Improved Voc of Cd-free cell dueto reduction of recombination inSCR by introducing
• K-treatment• (Zn,Mg)O for the 2nd buffer
R. Kamada et al., 43rd IEEE PVSC (2016)
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 18
Certified record efficiencies
22.0% Cd-free 22.3% with CdS buffer
1st buffer 2nd buffer η(%)
VOC(mV)
JSC(mA cm-2)
FF(%)
Prev. Cd-free Zn(O,S,OH) ZnO 20.9 685.8 39.9 76.5
New CdS CdS ZnO 22.3 721.9 39.4 78.2
New Cd-free Zn(O,S,OH) (Zn,Mg)O 22.0 717.0 39.4 77.9
R. Kamada et al., 43rd IEEE PVSC (2016)
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 19
Latest achievement and summary of recent progress in SF
Year K-treatment 1st Buffer 2nd Buffer η (%) Voc (mV) Jsc (mA/cm2) FF (%) Test Lab.
2012 n/a Cd-free ZnO 19.7 683 37.1 77.8 NREL, AIST
2014 n/a Cd-free ZnO 20.9 686 39.9 76.5 FhG-ISE
2015 ○ CdS ZnO 22.3 722 39.4 78.2 FhG-ISE
2016 ○ Cd-free (Zn,Mg)O 22.0 717 39.4 77.9 FhG-ISE
2016 ○ CdS (Zn,Mg)O 22.7 704 41.6 77.4 in-house
2016 ○ Cd-free (Zn,Mg)O 22.8 711 41.4 77.5 in-house
World RecordEfficiencies
19.7%Cd-free
20.9%Cd-free
22.3%CdS
TCO & absorberimprovement
(Zn,Mg)O
K-treatment(Zn,Mg)O
Even higher performance was obtained by further optimization (in-house measurement). Cd-free cell can outperform CdS cell. Encouraging result for SF’s product update in the future.
WR:ZSW’s22.6%
22.8% (in-house)Cd-free
22.7% (in- house)CdS
22.0%Cd-free
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 20
Our upward trail in the “efficiency map”
Electrical EfficiencyElectrical Efficiency
Both optical and electrical efficiencies have been improved so far.• optical loss reduction by absorber & TCO optimization• electrical loss reduction by absorber improvement & K-treatment
What’s next: electrical efficiency (Voc and FF) should be enhanced
Opt
ical
Eff
icie
ncy
Opt
ical
Eff
icie
ncy
GaAsc-Si
CdTe
Si-HJ
Recent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier | T. Kato | 7th IW-CIGSTech 2016/6/23 21
Summary
Solar Frontier’s recent progress was reviewed.
ManufacturingNew Tohoku plant with the latest technology begins commercial production.
Cd-free submodule developmentCertified efficiency of 18.6% has been achieved on 40cm2 submodule.22.8% technology will be transferred to further increase the efficiency.
Record cell developmentK-treatment and (Zn,Mg)O were introduced to increase both Voc and Jsc.
• Certified: 22.3% (CdS) & 22.0% (Cd-free)• Preliminary (in-house): 22.7% (CdS) & 22.8% (Cd-free)
Electrical loss seems to be still significant and should be improved next.
AcknowledgementThis work is partly consigned from the NEDO PV R&D programs.