Compositional depth profiles of chemiplated Cu2S/(Zn,Cd)S heterojunction solar cells

Atomic absorption spectroscopy combined with controlled chemical etching and Auger electron spectroscopy profiling with ion beametching have been used to obtain composition versus depth analyses of Cu2S/(Zn,Cd)S heterojunctionsolar cells formed by an aqueous cation exchange, or chemiplating, process. The Cu2S films, ranging from 0.5 to 6 _m in thickness, were polycrystalline and exhibited a (001) preferred orientation on either textured polycrystalline or cleaved single crystal (Zn,Cd)S substrates. The profiling results showed that the interfacial regions were compositionally graded over very large distances ranging from tens to hundreds of nonometers depending on the Cu2S film thickness. This is much wider than observed for comparable Cu2S/CdS cells. Moreover, excess Zn in the form of both elemental Zn and ZnS was always found in the interfacial region and may be responsible for the short circuit current being lower than expected for these cells.