Tailoring the CdS/CdSe/CdTe multilayer structure for optimization of photovoltaic device performance guided by mapping spectroscopic ellipsometry

Thin film CdTe superstrate solar cells have been fabricated by sputtering starting from CdS/CdSe front layers deposited on transparent conductor coated glass. The performance of such devices is sensitive to the fabrication details including temperature-time profile, which leads CdSe/CdTe interdiffusion and formation a CdTe1-xSex bandgap-graded absorber. Mapping spectroscopic ellipsometry (M-SE) has applied CdS CdSe thin films for process calibration, involves determining deposition rate in terms effective thickness (volume/area) versus spatial position sample. goal optimize correlating cell parameters with these two thicknesses. Intended variations thicknesses along unintended non-uniformities enable coarse fine-scale optimization, respectively. Using methods, highest CdS/CdSe/CdTe structure are obtained 13 nm 100 CdSe. An increase above decrease open-circuit voltage fill-factor attributed CdSe1-zSz region z approaching 0.5, where alloy electronic properties likely suffer. Our results demonstrate that M-SE, exploited conjunction non-uniformities, serve as viable approach optimization complex structures.