Study of the defect levels, electrooptics, and interface properties of polycrystalline CdTe and CdS thin films and their junction [solar cells]

In this study, the electrical behavior of CdS/CdTe junctions was investigated using deep-level transient spectroscopy (DLTS) and capacitance-voltage (c-v) measurements. The results were then correlated to chemical composition and optical properties (measured by wavelength-scanning ellipsometry) of the CdTe film and the dominant defect states were determined by photoluminescence (PL) emission measured before and after post-deposition CdCl₂ treatments. CdTe films used in this study were prepared by electrochemical deposition (ED), close-spaced sublimation (CSS) and physical vapor deposition (PVD). The chemical and heat treatments are shown to decrease Cd-vacancy levels (PL measurements) and quench majority-carrier deep traps. These treatments, which determine various parameters crucial to the device performance such as the type and concentration of the dominant defects and deep levels, greatly affect the device performance by controlling open-circuit voltage