Solar Energy (태양에너지)

The Korean Solar Energy Society (한국태양에너지학회)
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Effects of Sodium and Gallium on Characteristics of CIGS Thin Films and CdS/CIGS Solar Cells by Co-evaporation Method

Na확산과 Ga첨가에 따른 동시진공증발법으로 제조된 CIGS 박막과 CdS/CIGS 태양전지의 특성

  • Kwon, S.H. (New Energy Research Department, Korea Institute of Energy Research) ;
  • Lee, J.C. (New Energy Research Department, Korea Institute of Energy Research) ;
  • Kang, K.H. (New Energy Research Department, Korea Institute of Energy Research) ;
  • Kim, S.K. (New Energy Research Department, Korea Institute of Energy Research) ;
  • Yoon, K.H. (New Energy Research Department, Korea Institute of Energy Research) ;
  • Song, J.S. (New Energy Research Department, Korea Institute of Energy Research) ;
  • Lee, D.Y. (Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology) ;
  • Ahn, B.T. (Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology)
  • 권세한 (한국에너지기술연구소 신발전연구부) ;
  • 이정철 (한국에너지기술연구소 신발전연구부) ;
  • 강기환 (한국에너지기술연구소 신발전연구부) ;
  • 김석기 (한국에너지기술연구소 신발전연구부) ;
  • 윤경훈 (한국에너지기술연구소 신발전연구부) ;
  • 송진수 (한국에너지기술연구소 신발전연구부) ;
  • 이두열 (한국과학기술원 재료공학과) ;
  • 안병태 (한국과학기술원 재료공학과)
  • Published : 2000.06.30
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Abstract

We prepared and characterized $Cu(In_{1-x}Ga_x)Se_2$(CIGS) films using a elemental co-evaporation method for absorbing layer of high efficiency thin film solar cells. The CIGS films deposited on a soda-lime glass exhibited low resistivity because of higher carrier concentration. Na was accumulated at the CIGS surface and the 0 and Se were also accumulated at the surface, suggesting that oxidation is a driving force of Na accumulation. The structure of CIGS film was modified or a secondary phase was formed in the Cu-poor CIGS bulk films probably due to the incorporation of Na into Cu vacancy sites. As the Ga/(In+Ga) ratio increased, the diffraction peaks of $Cu(In_{1-x}Ga_x)Se_2$ films were shifted to larger angle and splitted, and the grain size of $Cu_{0.91}(In_{1-x}Ga_x)Se_2$ films became smaller. All $Cu_{0.91}(In_{1-x}Ga_x)Se_2$ films showed the p-type conductivity regardless of the Ga/(In+Ga) ratio. Ag/n-ZnO/i-ZnO/CdS/$Cu_{0.91}(In_{0.7}Ga_{0.3})Se_2$/Mo solar cells were fabricated. The currently best efficiency in this study was 14.48% for $0.18cm^2$ area ($V_{oc}=581.5mV,\;J_{sc}=34.88mA$, F.F=0.714).

동시 진공증발법을 이용하여 coming glass, soda-lime glass, Mo가 증착된 soda-lime glass 위에 $Cu(In_{1-x}Ga_x)Se_2$ 박막을 증착하였다. Soda-lime glass 위에서 제조된 $Cu(In_{0.5}Ga_{0.5})Se_2$ 박막의 전기비저항값과 정공농도는Cu/(In+Ga)비에 큰 영향을 받지 않았다. Soda-lime glass위에서의 $Cu(In_{1-x}Ga_x)Se_2$ 박막내부와 표면에는 Na이 검출되었고, 표면의 Na는 산소와 결합하고 있었으며, Cu가 부족한 조성에서 이차상이 형성되었다. Ga/(In+Ga)비가 증가할수록 $Cu(In_{1-x}Ga_x)Se_2$ 박막은 회절 peak들의 큰 회절각으로 이동, 초격자 peak등의 분리, 결정립 크기의 감소가 관찰되었다. $Cu_{0.91}(In_{1-x}Ga_x)Se_2$ 박막은 Ga/(In+Ga)비에 무관하게 전기적으로 p-type을 나타내었다. Ag/n-ZnO /i-Zno/CdS/$Cu_{0.91}(In_{0.7}Ga_{0.3})Se_2$/Mo/glass구조의 태양전지를 제조하였으며, 태양전지변환효율(Eff.) = 14.48%, 단락전류밀도(Jsc) = $34.88mA/cm^2$, 개방전압(Voc) =581.5 mV, 충실도(F.F) = 0.714을 나타내었다.

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