Recent Research Progress of High-efficiency CIGS Solar ... · PDF fileRecent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier 7th International Workshop on CIGS

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



Small Cell~0.5cm2



~90×120cm2

~60×120cm2


MP3 (900MW)MP4 (150MW)

22.3%(CdS)

22.0%(Cd-free)

18.6%(Cd-free)

22.7% in-house(CdS)


(Aperture Area)



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


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


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 $



Small Cell~0.5cm2



~90×120cm2

~60×120cm2


MP3 (900MW)MP4 (150MW)

22.3%(CdS)

22.0%(Cd-free)

18.6%(Cd-free)

22.7% in-house(CdS)


(Aperture Area)




Small Cell~0.5cm2



~90×120cm2

~60×120cm2


MP3 (900MW)MP4 (150MW)

22.3%(CdS)

22.0%(Cd-free)

18.6%(Cd-free)

22.7% in-house(CdS)


(Aperture Area)



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…



Small Cell~0.5cm2



~90×120cm2

~60×120cm2


MP3 (900MW)MP4 (150MW)

22.3%(CdS)

22.0%(Cd-free)

18.6%(Cd-free)

22.7% in-house(CdS)


(Aperture Area)




Small Cell~0.5cm2



~90×120cm2

~60×120cm2


MP3 (900MW)MP4 (150MW)

22.3%(CdS)

22.0%(Cd-free)

18.6%(Cd-free)

22.7% in-house(CdS)


(Aperture Area)



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)


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


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)


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)


(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



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



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



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


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


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.

Recent Research Progress of High-efficiency CIGS Solar ... · PDF fileRecent Research Progress of High-efficiency CIGS Solar Cell in Solar Frontier 7th International Workshop on CIGS

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