Study of interdiffusion reaction at the CdS/CdTe interface

To detect the relatively strong scattering signals of the Raman scattering and the x-ray diffraction (XRD) from CdS and those from the CdS/CdTe interface, an inverted CdTe solar cell structure was prepared and a 35-nm-thick CdS film was deposited on the surface of a CdTe solar cell structure. The Raman and high-resolution XRD scattering spectra allowed us to qualitatively study the interdiffusion and its related reactions at the CdS/CdTe interface. Interdiffusion began to occur at a relatively low temperature of about 350 °C, which coincided with the CdS phase transformation from cubic to hexagonal phase. Substantial interdiffusion of S and Te occurred after heat treatment at a temperature of 550 °C, resulting in formation of S-rich and Te-rich CdSxTe1−xalloy at the CdS/CdTe interface, with S and Te atomic concentration of ∼9% and 11% diffused into the CdTe and the CdS films, respectively.