Cu(InGa)Se2 thin-film solar cells with continuously evaporated Cd-free buffer layers

In_xSe_y (IS) and ZnIn_xSe_y (ZIS) were prepared as the buffer layer for Cu(InGa)Se₂ (CIGS) thin-film solar cells without the use of Cd. These buffer layers can be sequentially deposited on a CIGS thin-film absorber layer in the same fabrication apparatus. The performance of the CIGS thin-film solar cells with these buffer layers was affected by annealing both before and after deposition of a ZnO window layer. Annealing in air at 200°C for 1 hour before the deposition of ZnO resulted in relatively stable and high efficiencies of over 12%. The solar cell with a high fill factor of over 0.75 was obtained using a coevaporated ZIS buffer layer. An efficiency of 13.0% was achieved using a coevaporated IS buffer layer without using a chemical bath deposition method