Substrate-Type Hydrogenated Amorphous Sige Thin Film Solar Cells With Ge-Graded Sige Layers On Opaque Substrates

a-SiGe: H thin film solar cells with a light-abosrbing layer having differently graded Ge-compostion (C-Ge)-profiles were fabricated to investigate the effect of C-Ge-profiling on the cell performance and light-induced degradation (LID). The C-Ge-profiles were linear normal profiling, nonlinear normal profilings, nonlinear reverse profiling, and nonlinear U-shape profiling. The cells with these CGe-profiles were compared to the cells with a constant C-Ge. Among the samples, the cells with normal profilings showed better performances than the others. The efficiencies of the cells with linear and nonlinear normal profilings were 6.31 and 6.10%, respectively. Compared to the cells with constant-C-Ge, the efficiency of the cells with normal profiling was increased mainly due to the increase in the fill factor, which could be induced by the enhancement of internal field. The light-soaking experiment also showed that C-Ge-profilings can reduce LID. In this work, the use of a light-absorbing layer with graded C-Ge-profiling could improve the cell performance in terms of both efficiency and LID.