ESI-1

Electronic supplementary information (ESI) for

Achieving Over 4% Efficiency for SnS/CdS Thin-Film Solar

Cells by Improving Heterojunction Interface Quality

Jae Yu Cho,a SeongYeon Kim,b Raju Nandi,a Junsung Jang,a Hee-Sun Yun,c,d

Enkhjargal Enkhbayar,b Jin Hyeok Kim,a Doh-Kwon Lee,c,d Choong-Heui Chung,e

JunHo Kim,b,* and Jaeyeong Heoa,*

aDepartment of Materials Science and Engineering, and Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 61186, Republic of KoreabDepartment of Physics, Incheon National University, Incheon 22012, Republic of Korea

cPhoto-electronic Hybrids Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea

dDivision of Nano and Information Technology, KIST School Korea University of Science and Technology, Seoul 02792, Republic of Korea

eDepartment of Materials Science and Engineering, Hanbat National University, Daejeon 34158, Republic of Korea

* Corresponding authorE-mail: jhk@inu.ac.kr (Prof. J. Kim)E-mail: jheo@jnu.ac.kr (Prof. J. Heo)

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2020

mailto:jhk@inu.ac.krmailto:jheo@jnu.ac.kr

ESI-2

2.0 2.5 3.0 3.5 4.0

(h

)2

Energy (eV)

RT (3.49 eV) 100 oC (3.63 eV) 200 oC (3.76 eV) 300 oC (3.71 eV) 400 oC (3.65 eV)

0 100 200 300 40010-4

10-3

10-2

Deposition temperature (oC)

Resistivity (.cm)

0.0

2.0x1020

4.0x1020

6.0x1020

8.0x1020

1.0x1021

Carrier concentration (cm-3)

5

10

15

20

25

Carrier mobility (cm2.V-1.s-1)

300 400 500 600 700 8000

20

40

60

80

100 T

rans

mitt

ance

(%)

Wavelength (nm)

RT (87.8%) 100 oC (89.9%) 200 oC (91.0%) 300 oC (93.2%) 400 oC (93.4%)

(a) (b) (c)

Fig. S1. (a) Transmittance spectra, (b) bandgap extraction, and (c) electrical properties of the AZO films

grown at different temperatures from room temperature to 400 °C.

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0.0 0.1 0.2 0.3 0.40

5

10

15

20

25Cu

rrent

den

sity

(mA

cm2

)

Voltage (V)

(a)

0.0 0.1 0.2 0.3 0.40

5

10

15

20

25

Curre

nt d

ensit

y (m

A cm

2)

Voltage (V)

(b)

0.0 0.1 0.2 0.3 0.40

5

10

15

20

25

Curre

nt d

ensit

y (m

A cm

2)

Voltage (V)

(c)

0.0 0.1 0.2 0.3 0.40

5

10

15

20

25

Curre

nt d

ensit

y (m

A cm

2)

Voltage (V)

(d)

0.0 0.1 0.2 0.3 0.40

5

10

15

20

25

Curre

nt d

ensit

y (m

A cm

2)

Voltage (V)

(e)

Fig. S2. J–V characteristics of the SnS/CdS TFSCs at different AZO film deposition temperatures of (a)

150 °C, (b) 200 °C, (c) 250 °C, (d) 300 °C, and (e) 350 °C.

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Mo

SnS

i-ZnO/AZOCdS

1 m Mo

SnS

i-ZnO/AZOCdS

1 m

(a) (b)

Fig. S3. Cross-sectional SEM images of the SnS/CdS TFSCs with AZO films deposited at (a) 150 °C and

(b) 300 °C.

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0 500 1000 1500103

104

105

Inte

nsity

(c/s

)

Time (s)

Sn (250 oC) S (250 oC) Cd (250 oC) Sn (350 oC) S (350 oC) Cd (350 oC)

103

104

105

Inte

nsity

(c/s

)

Time (arb. unit)

Sn (250 oC) S (250 oC) Cd (250 oC) Sn (350 oC) S (350 oC) Cd (350 oC)

0 500 1000 1500 2000101

102

103

104

105

106

Zn Mo Cd Sn

Inte

nsity

(c/s

)

Time (s)

O Na Al S

0 500 1000 1500 2000101

102

103

104

105

106

Zn Mo Cd Sn

Inte

nsity

(c/s

)

Time (s)

O Na Al S

(a)

(b)

(c)

(d)

SSn

Cd

Fig. S4. Full SIMS depth profiles of the TFSCs with AZO deposited at (a) 250 and (b) 350 oC without Al

top contact. (c) The selected profiles for Sn, S, and Cd ions. (d) The shifted profiles for matching the

initial detection of S, Sn, and Cd signals to evaluate the Cd diffusion into SnS absorbers. Slight Cd

diffusion into SnS absorber is noted for the 350 oC device.

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50

60

70

80

90

100

110

54.7

65.3

80.1

101.397.3

350300250200

Effi

cien

cy re

tent

ion

(%)

AZO deposition temperature (oC)1500.0 0.1 0.2 0.3 0.4

0

5

10

15

20

25

C

urre

nt d

ensi

ty (m

A c

m-2)

Voltage (V)

150 oC 200 oC 250 oC 300 oC 350 oC

2018.05. 2020.04.

(a) (b)

Fig. S5. (a) J–V characteristics and (b) the efficiency retention of SnS/CdS TFSCs at various AZO film

deposition temperatures of 150–350 °C. To test the long-term stability of the TFSCs, the device

performance was measured again after almost two years.

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0 50 100 150 200 250 3000.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0 V o

c (V)

Temperature (K)

AZO deposition temperature 150 C 200 C 250 C 300 C 350 C

150 200 250 300 3500.5

0.6

0.7

0.8

0.9

EA (e

V)

AZO deposition temperature (C)

(a) (b)

Fig. S6. (a) Temperature dependence of Voc for TFSCs with various AZO deposition temperatures at 150

to 350 °C. (b) The extracted activation energy as a function of AZO deposition temperature.

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5 m 5 m

(a) (b)

Fig. S7. Plan-view SEM images of the SnS absorbers annealed in (a) vacuum condition (~10-2 Torr), and

(b) 20 Torr in Ar ambient, respectively. Partial evaporation of SnS surface is observed for (a) vacuum

condition.

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300 400 500 600 700 8000

20

40

60

80

100

Tran

smitt

ance

(%)

Wavelength (nm)

2 3 4

(h

)2 Energy (eV)

3.58 eV

Fig. S8. Transmittance spectrum of the AZO layer grown in a home-made sputter at room temperature;

the inset shows the bandgap extraction plot (Eg = 3.58 eV). The average transmittance for 400 – 700 nm

was 89.0%. The film thickness was ~380 nm and the sheet resistance was 28 ohm/sq. with resistivity of

1.066 × 10-3 ohm cm.

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0.0 0.1 0.2 0.3 0.40

5

10

15

20

25

Cur

rent

den

sity

(mA

cm

-2)

Voltage (V)

(a)Best cellVoc = 0.249 VJsc = 15.6 mA cm-2FF = 0.524 = 2.04%

0.0 0.1 0.2 0.3 0.40

5

10

15

20

25

Cur

rent

den

sity

(mA

cm

-2)

Voltage (V)

(b)Best cellVoc = 0.217 VJsc = 14.5 mA cm-2FF = 0.512 = 1.61%

0.0 0.1 0.2 0.3 0.40

5

10

15

20

25

Cur

rent

den

sity

(mA

cm

-2)

Voltage (V)

(c)

Best cellVoc = 0.332 VJsc = 22.1 mA cm-2FF = 0.575 = 4.20%

Fig. S9. J–V characteristics of the TFSCs with (a) as-deposited SnS/CdS without any junction annealing,

(b) annealed SnS at 300 °C in Ar ambient and as-deposited CdS without any junction annealing, and (c)

as-deposited SnS/CdS with additional junction annealing at 300 °C in Ar ambient. Here, the annealing

duration and pressure was fixed at 1 h and 20 Torr, respectively, and in total, six cells were fabricated.

The highest efficiencies achieved for these devices were 2.04%, 1.61%, and 4.20%, respectively.

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(a) (b)

Fig. S10. (a) J–V and (b) EQE certifications of the champion cell ( = 4.225%) measured at KIER in

Korea.

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200 400 600 800 1000 1200 14000

20

40

60

80

100

T,R,

A (%

)

Wavelength (nm)

T R A

Glass/FTO

200 400 600 800 1000 1200 14000

20

40

60

80

100Glass/FTO/CdS

T,R,

A (%

)

Wavelength (nm)

T R A

200 400 600 800 1000 1200 14000

20

40

60

80

100

T,R,

A (%

)

Wavelength (nm)

T R A

Glass/i-ZnO/AZO

200 400 600 800 1000 1200 14000

20

40

60

80

100R

(%)

Wavelength (nm)

Glass/Mo/SnS/CdS/i-ZnO/AZO(a) (b)

(c) (d)

Fig. S11. (a) Reflectance spectrum of the full device without a top metal grid. Transmittance, reflectance,

and absorbance spectra for (b) glass/i-ZnO/AZO, (c) glass/FTO, and (d) glass/FTO/CdS. Figure (b) was

used for calculating absorption in the transparent electrodes (i-ZnO/AZO). Figure (c) and (d) were used

for calculating absorption in CdS buffer layer.

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Table S1. Electrical properties of AZO thin films grown at different temperatures.

AZO filmdeposition

Temperature (°C)

RT 100 200 300 400

Thickness(nm)

494 491 406 435 405

Rsheet

(Ω/sq.)

55.1 16.0 7.8 11.7 21.9

Resistivity(Ω cm)

2.72 × 10-3 7.86 × 10-4 3.17 × 10-4 5.09 × 10-4 8.87 × 10-4

Carrier concentration

(cm-3)2.2 × 1020 5.4 × 1020 9.6 × 1020 6.2 × 1020 6.4 × 1020

Mobility(cm2 V-1s-1)

9.8 14.5 20.6 19.5 10.9

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Table S2. Simulated diode parameters for SnS/CdS TFSCs at various AZO film deposition temperatures

from 150 °C to 350 °C.

AZO film deposition temperature

(°C)

Gsh(mS cm-2)

Rs(Ω cm2)

A J0(mA cm-2)

150 2.430 0.491 1.228 2.23 × 10-2

200 2.795 0.534 1.215 1.27 × 10-2

250 2.214 0.441 1.424 1.66 × 10-3

300 1.073 0.707 1.244 3.63 × 10-3

350 0.289 0.710 1.241 2.88 × 10-3