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  Kieven, D.; Grimm, A.; Lauermann, I.; Rissom, T.; Klenk, R.: Band alignment at Sb₂S₃/Cu(In,Ga)Se₂ heterojunctions and electronic characteristics of solar cell devices based on them. Applied Physics Letters 96 (2010), p. 262101/1-3

10.1063/1.3457439

Abstract:
Band offsets at Sb2S3 / Cu(In,Ga)Se2 heterojunctions have been studied by x-ray and ultraviolet photoemission spectroscopy. The valence and conduction band offset have been estimated to -(0.6+- 0.3 eV and (0.2+- 0.3 eV), respectively. This result suggests Sb2S3 as a potential buffer layer material for chalcopyrite based solar cells. However, Cu(In,Ga)Se2 / Sb2S3 / ZnO solar cells have been investigated. While the open circuit voltage ranged up to ϳ0.4– 0.5 V, the short circuit current was limited to ϳ1.8– 4.9 mA/ cm2. A photocurrent of about 30 mA/ cm2 was found for negative bias. On the basis of bias dependent quantum efficiency measurements and calculations, limiting mechanisms are discussed.