Thermochemical and Kinetic Aspects of Cadmium Telluride Solar Cell Processing

Abstract

ABSTRACTA chemical and kinetic basis underlying processing strategies for thin film polycrystalline CdTe/CdS solar cell fabrication is presented. The processing conditions employed for moderate and high conversion efficiency CdTe/CdS solar cells fall within a consistent framework based on temperature and concentration of CdCl2 and O2 species during film deposition or thermal treatment. Detailed microstructural and compositional results are compared for thin-film CdTe/CdS structures with CdTe deposited by physical vapor deposition, electrodeposition and close-space sublimation. X-ray diffraction coupled with a model for diffusion of CdS into CdTe is used to determine the effect of treatment conditions on bulk and grain boundary diffusion coefficients. The effects of CdS diffusion, oxides, recrystallization and grain growth with respect to device efficiency, stability and process control over large area are discussed.