摘要
Control of Se content during manufacturing process has been known to determine the efficiency of Cu(In x Ga 1-x )Se 2 (CIGS) solar cells. However, how Se is distributed in CIGS films and how Se distribution in hundred-nanometer scale affects the cell performance have not been realized due to limited spatial resolution of composition mapping technique. In this study, a promising nondestructive analysis by using field-emission electron probe microanalysis (FE-EPMA) is first demonstrated to directly probe the Se distribution within the depletion region of CIGS absorbers. We observe that Se-deficient-related defects are still exist in CIGS films even with high Se concentration but non-uniform distribution, leading to relatively low efficiency (~7%). By correlating photoluminescence spectra and conductivity mapping with composition distribution, we clarify that the uniform Se distribution is the key factor to suppress the defect formation and to enhance the p-n inversion at grain boundaries, resulting in significant efficiency boost to 12%.