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1 Jurnal f the Krean Ceramic Sciety Vl. 48, N. 4, pp. 328~333, DOI: /KCERS Effect f Degraded Al-dped ZnO Thin Films n Perfrmance Deteriratin f CIGS Slar Cell Dwan Kim, Dng-wn Lee*, Hees Lee, Seungtae Kim**, Chi-hng Park**, and Yng-nam Kim* Schl f Materials Science and Engineering, Pusan Natinal University, Busan , Krea *Material Testing Center, Krea Testing Labratry, Seul , Krea **Slar Cell Labratry, LG Inntek C., Ltd., Osan , Krea (Received June 8, 2011l; Resived July 16, 2011; Accepted July 25, 2011) š š š y ü ZnO:Al n yƒ CIGS x k w e w ½ Á *Á Á½ k**á y**á½ û* w œw *w» x sƒ l **LG l Slar Cell Lab. ( ; ; k) ABSTRACT The influence f Al-dped ZnO (AZO) thin films degraded under high temperature and damp heat n the perfrmance deteriratin f Cu(In,Ga)Se 2 (CIGS) slar cells was investigated. CIGS slar cells with AZO/CdS/CIGS/M structure were prepared n glass substrate and expsed t high temperature (85 C) and damp heat (85 C/85% RH) fr 1000 h. As-prepared CIGS slar cells had 64.91% in fill factr (FF) and 12.04% in cnversin efficiency. After expsed t high temperature, CIGS slar cell had 59.14% in FF and 9.78% in efficiency, while after expsed t damp heat, it had 54.00% in FF and 8.78% in efficiency. AZO thin films in the deterirated CIGS slar cells shwed increases in resistivity up t 3.1 times and 4.4 times cmpared t their initial resistivity after 1000 h f high temperature and damp heat expsure, respectively. These results can be explained by the decreases in carrier cncentratin and mbility due t diffusin r adsrptin f xygen and misture in AZO thin films. It can be inferred that decreases in FF and cnversin efficiency were caused by an increase in series resistance, which resulted frm an increase in resistivity f AZO thin films degraded under high temperature and damp heat. Key wrds: CIGS thin film slar cell, Al-dped ZnO, High temperature, Damp heat, Degradatin 1. k w Si Á w x k w š. x k g x k, yw k w. yw Cu(In,Ga)Se 2 (CIGS) x wš p Ÿ ( cm ) ƒ» x k 1 Ÿ d š. 1), Si k w ZnO/CdS/CIGS/M CIGS Crrespnding authr : Yng-nam Kim ynkim@ktl.re.kr Tel : Fax : x k w w w š. 2) ZnO t n y (Transparent cnducting xide; TCO) wù ˆ (3.37 ev) w», Ÿw p w sq q v, k, Ÿ Ÿ œw š. 3,4) Indium tin xide (ITO) w ƒ w ZnO ITO wù» Ÿn w j» w w w š. 5) p, Al-dped ZnO (AZO)» ƒ Ÿ Ÿn, ITO w ƒ wš ƒƒ j û. 6) w AZO k n š, w CIGS x k w» w w š. 7,8) 328

2 š š š y ü ZnO:Al n yƒ CIGS x k w e w 329 k»» y w, e y,, y p,,,» p. w w p 9) l k yw» w w w š š, k w w š. ù k» p 10) w e n w œ y w w n ü y ¾». 11,12), CIGS x k AZO w n yƒ k w e w w š w. š š š y CIGS x k w n AZO» p y w ³ wš w. 2. x AZO/CdS/CIGS/M/glass CIGS x k (LG l) w š š š ü x ww. š x š š x ü x (Challenge 250, ACS) w ƒƒ 85 C 85 C/85% RH 1000 ww š 50, 100, 150, 200, 400, 600, 800, 1000 z w p sƒ ww. CIGS x k w ü x z š (Fill factr; FF) yz (Cnversin efficiency; Eff) d w. k ü n AZO w, e Hall effect measurement system (HMS-3000, Ecpia) w d w. CIGS k AZO FE-SEM (S-4700, Hitachi) w w š, X-ray diffractmeter (X pert PRO, Panalytical) w AZO y w. 3. š Fig. 1. Crss-sectinal image f CIGS slar cell with ZnO:Al/ CdS/CIGS/M/glass structure. CIGS x k w š š š y ü x z š yz d w š Table 1 ùkü. CIGS x k» š yz ƒƒ 64.91% 12.04%. 85 C š 1000 z š yz ƒƒ 59.14% 9.78% w 85 C 85%RH š š 1000 z ƒƒ 54.00% 8.78% j w. š y š š y CIGS x k wƒ j w š š y sw w yƒ w w» q., š š š y CIGS k w ³ w» w n AZO d w» ww. š š š y y AZO w, e y Hall effect measurement system w d w š, Fig. 2 Fig. 3 ùkü. Fig. 2 AZO» w Ω cm û ùk 4 ü š š š y ƒ w w j ƒw w ùkü. Fig. 1 AZO/CdS/CIGS/M/glass CIGS x k. ̃ 1.8 µm CIGSd w w M z d x š, AZO n d CdS buffer layerd x. ù AZO n d CdS buffer layerd. Table 1. Variatin in Fill Factr and Cnversin Efficiency f CIGS Slar Cell Befre and after Degradatin Fill factr (%) Cnversin Efficiency (%) As-prepared Degraded at 85 C fr 1000 h Degraded at 85 C/85% RH fr 1000 h «4y(2011)

3 330 ½ Á Á Á½ ká yá½ û Fig. 2. Variatin in resistivity f AZO thin films in CIGS slar cells as a functin f degradatin time. Fig. 3 y w, 85 C š w 100 ¾ e yƒ» w yƒ 100 z l e ƒ w» e w w ƒ w. 85 C/85% RH š š w» l e ƒ w» w» l ƒw w ùkü. p,» 100 e ƒ w š, 100 z l e ƒ w. 85 C 85 C/85% RH ƒƒ 1000 z AZO n w Ω cm ƒw. š š š w AZO n w ƒw e ƒ w», AZO ü y enw ù t w x 13).» ƒ AZO y dnr w w e ƒ w ) w, AZO t szw» e k (scattering center) w» k. 11,17) š y AZO n w ƒƒ y w w š š y y l j w. p, ZnO w yw j. 18) AZO yw H + O 2 H + OH x wš AZO ü interstitial psitin ew quasi szw w Fig. 3. Variatin in (a) carrier cncentratin and (b) hall mbility f AZO thin films in CIGS slar cells as a functin f degradatin time. ew e jš szw. 16,19), w š y AZO š š y AZO w j ƒw. š š š CIGS x k wƒ j w š š y AZO n w ƒƒ f». AZO/CdS/CIGS/M/glass ƒ k n AZOd w ƒw k w ƒ w Fill factrƒ w k z w. š š š y AZO t ƒ y w yw Fig. 4 ù kü. y w» AZO t» x ƒ w w wz

4 고온 및 고온고습 환경 내에서 ZnO:Al 투명전극의 열화가 CIGS 박막형 태양전지의 성능 저하에 미치는 영향 Fig. 4. Surface mrphlgy f AZO thin films in CIGS slar cells with degradatin time. 입자들로 구성되어 있었다. 85 C의 고온 조건에 노출된 경 우 열화시간에 상관없이 미세구조적인 변화를 관찰할 수 없었다. 그러나 85 C/85% RH의 고온고습 조건에 노출된 경우에는 열화시간 경과에 따라 부분적으로 돌기 형태의 미세한 결정입자들이 소멸되는 것을 관찰할 수 있었다. Fig. 5를 통해 고온 및 고온고습 조건에 노출된 CIGS 박막형 태 양전지 단면의 미세구조 변화를 확인할 수 있다. 두 가지 스 트레스 모두에서 열화시간에 상관없이 CIGS층과 M 후 면전극 층 사이의 계면은 특이한 변화 없이 명확하게 관 찰되었다. 그러나 이와 달리 초기에 명확하게 관찰되었던 AZO/CdS층과 CIGS층 사이의 계면은 고온고습 환경에 노 출된 경우에만 시간이 경과함에 따라 점차 불분명해지다가 소멸되는 것을 확인할 수 있었다. 마지막으로 Fig. 6에 나타낸 XRD 분석을 통해 고온 및 고온고습 환경에 노출된 AZO 투명전극의 결정구조 변화를 확인할 수 있었다. Fig. 6을 통해 AZO 박막의 초기 결정구 조를 살펴보면 주 피크인 (002) 면을 비롯하여 (101), (102), (103), (112) 등과 같은 결정 면들에 의한 회절피크들을 확 인할 수 있었다. 그러나 고온 및 고온고습 조건에 1000시간 동안 노출된 후에는 (002)면을 제외한 나머지 결정 면들의 회절피크 세기가 상대적으로 감소하였다. 특히, 고온에 노 출된 경우와 비교하여 고온고습 조건에 노출된 경우에는 Fig Crss-sectinal structure f CIGS slar cells with degradatin time. Fig. 6. X-ray patterns f AZO thin films in CIGS slar cells ntdegraded and degraded at 85C and 85C/85% RH fr 1,000 h. 제 48 권 제4호(2011)

5 332 ½ Á Á Á½ ká yá½ û (002) w ù j w. š š š y AZOd ü mw c w ƒ yw w. ww CIGS x k ü AZO n š š š y e w w ƒw y w š,, y x l w q. š wì yƒ AZO n w ƒ w y w. w, š š y w š y AZO n yƒ w. 4. š š š CIGS x k w AZO n» p y w š w. š š š» ü, AZO y» e ƒ w AZO n w ƒ w. p, š š y AZO w j ƒw, yw w. CIGS x k n w ƒw w ƒ w» Fill factr yz w. w, CIGS x k ƒ š š š y AZOn y w w ƒ w p, š š y w AZO n CIGS x k y ƒ y g. Acknwledgment LG l( ) w,. REFERENCES 1. J. H. Kim, Cmpsite Semicnductr CIGS Thin Film Slar Cell (in Krean), Ceramist, 13 [3] (2010). 2. S. K. Kim, J. C. Lee, K. H. Yn, J. S. Sng, S. H Kwn, and B. T. Ahn, A Study n the Fabricatin and Characterizatin f Cu(In x Ga 1 x )Se 2 Slar Cells by C-evapratin Methd (in Krean), Kr. Sl. Energ. Sc. Spring Cnference, (1998). 3. S. Fernandez, A. Martinez-Steele, J. J. Gandia, and F. B. Narani, Radi Frequency Sputter Depsitin f High-quality Cnductive and Transparent ZnO:Al Films n Plymer Substrates fr Thin Film Slar Cells Applicatins, Thin Slid Films, (2009). 4. T. Yanagisawa, T. Kjima, and T. Kyanagi, Behavir f Cu(In,Ga)Se 2 Slar Cells Under Light/damp Heat Over Time, Micrelectrn. Reliab., (2004). 5. S. Fay, J. Steinhauser, S. Niclay, and C. Ballif, Plycrystalline ZnO:B Grwn by LPCVD as TCO fr Thin Film Silicn Slar Cells, Thin Slid Films, (2010). 6. O. Nakagawara, Y. Kishimt, H. Set, Y. Kshid, Y. Yshin, and T. Makin, Misture-resistant ZnO Transparent Cnductive Films with Ga Heavy Dping, Appl. Phys. Lett., (2006). 7. F. J. Pern, B. T, S. H. Glick, R. Sundaramrthy, C. DeHart, S. Glynn, C. Perkins, L. Mansfield, and T. Gessert, Variatins in Damp Heat Induced Degradatin Behavir f Sputtered ZnO Windw Layer fr CIGS Slar Cells, Prc. SPIE, R 1-12 (2010). 8. F. J. Pern, S. H. Glick, X. Li, C. DeHart, T. Gennett, M. Cntreras, and T. Gessert, Stability f TCO Windw Layers fr Thin Film CIGS Slar Cells Damp Heat Expsures - part 3, Prc. SPIE, K 1-12 (2009). 9. K. C. Kang, J. S. Lee, G. H. Kang, C. S. Huh, and sg. J. Yu, Characteristic Evaluatin Tls f EVA Sheet fr Phtvltaic Mdule Fabricatin(in Krean), Kr. Sl. Energ. Sc. spring cnference, 92-7 (2008). 10. S. Kurtz, J. Granata, and M. Quintana, Phtvltaic Reliability R&D Tward a Slar Pwered Wrld, Sc. Phtgr. Instrum. Engi. Sl. Energ. Technl. Cnference Paper, NREL/CP (2009). 11. W. Lin, R. Ma, J. Xue, and B. Kang, RF magnetrn sputtered ZnO:Al Thin Films n Glass Substrates: A Study f Damp Heat Stability n Their Optical and Electrical Prperties, Sl. Energ. Mat. Sl. C., (2007). 12. J. Y. Jung and S. H Ch, Structural, Electrical, and Optical Prperties f AZO Thin Films Subjected t Rapid Thermal Annealing Temperature(in Krean), J. Kr. Inst. Electr. Electrn. Mater. Eng., (2010). 13. C. Guillen and J. Herrer, Stability f Sputtered ITO Thin Films t the Damp-heat Test, Surf. Cat. Tech., (2006). 14. D. G. Lim, G. S. Kang, S. I. Kwn, J. H. Yi, M. W. Park, and D. J. Kwak, The Effect f Heat Treatment n the Mrphlgical and Electrical Prperties f Aluminum-dped Zinc Oxide Films, J. Kr. Phys. Sc., (2007). 15. Y. N. Kim, H. G. Shin, J. K. Sng, D.H. Ch, and H.S. Lee, Thermal Degradatin Behavir f Indium Tin Oxide Thin Films Depsited by Radi Frequency Magnetrn Sputtering, J. Mater. Res., 20 [6] (2005). 16. S. S. Lee, Y. N. Kim, H. G. Shin, J. K. Sng, and H. S. Lee, Thermal Degradatin Behavir f Aluminum-dped Zinc Oxide Thin Films Prepare by Using a Sl-gel Prcess, J. Kr. Phys. Sc., 53 [1] (2008). 17. T. Thsphn, J. Hupkes, S. Calnan, W. Reetz, B. Rech, W. Beyer, and N. Sirikulrat, Damp Heat Stability and Annealing Behavir f Aluminum Dped Zinc Oxide Films Prepared by Magnetrn Sputtering, Thin Slid Films, w wz

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