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Layer Transfer of Cu(In,Ga)Se2 Thin Film and Solar Cell Fabrication

Cu(In,Ga)Se2 (CIGS) thin films were transferred to alternative substrates by a lift-off process, and solar cells were fabricated using the transferred films. CIGS films were grown on Mo/soda-lime glass (SLG) substrates by a three-stage evaporation process. The CIGS films were transferred to two alternative substrates: a rigid SLG and a flexible polyimide film. In the lift-off process, an intentional sacrificial layer between CIGS and Mo back contact layers was not prepared. CIGS solar cells with In2O3:Sn/ZnO/CdS/CIGS/Mo/conductive-epoxy/alternative-substrates structure were fabricated. Both solar cells showed almost half of the conversion efficiencies of a CIGS solar cell fabricated by a standard process. This is because of poor short circuit current and fill factor due to voltage-dependent current collection and high series resistance. Modifications of the composition profile of the CIGS layer and back contact property will improve the device performance. These results demonstrated the possibility of using the lift-off process for CIGS solar cells to widen the variety of substrate material choice.