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Chalcogenization-Derived Band Gap Grading in Solution-Processed CuInxGa1–x(Se,S)2 Thin-Film Solar Cells

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journal contribution
posted on 16.12.2015, 00:00 by Se Jin Park, Hyo Sang Jeon, Jin Woo Cho, Yun Jeong Hwang, Kyung Su Park, Hyeong Seop Shim, Jae Kyu Song, Yunae Cho, Dong-Wook Kim, Jihyun Kim, Byoung Koun Min
Significant enhancement of solution-processed CuInxGa1–x(Se,S)2 (CIGSSe) thin-film solar cell performance was achieved by inducing a band gap gradient in the film thickness, which was triggered by the chalcogenization process. Specifically, after the preparation of an amorphous mixed oxide film of Cu, In, and Ga by a simple paste coating method chalcogenization under Se vapor, along with the flow of dilute H2S gas, resulted in the formation of CIGSSe films with graded composition distribution: S-rich top, In- and Se-rich middle, and Ga- and S-rich bottom. This uneven compositional distribution was confirmed to lead to a band gap gradient in the film, which may also be responsible for enhancement in the open circuit voltage and reduction in photocurrent loss, thus increasing the overall efficiency. The highest power conversion efficiency of 11.7% was achieved with Jsc of 28.3 mA/cm2, Voc of 601 mV, and FF of 68.6%.