Photophysical Properties of CdSe/CdTe Bilayer Solar Cells: A Confocal Raman and Photoluminescence Microscopy Study

Understanding and controlling the optical and electrical properties of the solar cells, from the absorber layer to the complete devices, is one of the key elements for engineering high-efficiency devices. Such an understanding, especially the correlation between device performance and optical-structural-morphological properties of film stack, is still lacking in the field of cadmium selenide/telluride alloy-based solar cells. Here, we report confocal Raman and photoluminescence microscopy study results obtained through exciting both film and glass sides of cadmium selenide and cadmium telluride bilayer device stacks treated with cadmium chloride. We show that the device stack, especially the glass side, losses significant charge carries to the recombination arising from uniformity issues related to material composition, energetics, and defects. Furthermore, there is a high energy tail emission peak originating from CdTe, and CdSe can suppress it significantly under
$\mathbf{CdCl}_{2}$
treatment.