Raman and RBS studies of interdiffusion in RF-sputtered CdS/CdTe solar cells

The performance of CdS/CdTe photovoltaic devices is strongly determined by the properties of the CdS/CdTe interface region which forms during the heat treatment of the solar cell. Due to interdiffusion of sulfur and tellurium across the original CdS/CdTe junction and the formation of CdSxTe1−x at the interface, material properties such as the bandgap and the absorption coefficient of the newly formed material will be changed. In order to improve our understanding of the interface and to be able to control it, near resonant Raman scattering on a series of single-phase CdSxTe1−x alloys was performed and the Stokes shifts of the longitudinal optical (LO) phonons were measured over the entire composition x. The data have been fitted according to the modified random element isodisplacement (MREI) model. The results gained from the investigation of the alloys have then been applied to study the CdS/CdTe interface region of sputter-deposited solar cells. The formation of a two-phase CdSxTe1−x alloy region at the...