The activation of thin film CdTe solar cells using alternative chlorine containing compounds

The re-crystallisation of thin film cadmium telluride (CdTe) using cadmium chloride (CdCl₂) is a vital process for obtaining high efficiency photovoltaic devices. However, the precise micro-structural mechanisms involved are not well understood. In this study, we have used alternative chlorine-containing compounds to determine if these can also assist the re-crystallisation of the CdTe layer and to understand the separate roles of cadmium and chlorine during the activation. The compounds used were: tellurium tetrachloride (TeCl₄), cadmium acetate (Cd(CH₃CO₂)₂), hydrochloric acid (HCl) and zinc chloride (ZnCl₂). TeCl₄ was used to assess the role of Cl and the formation of a Te-rich outer layer which may assist the formation of the back contact. (Cd(CH₃CO₂)₂) and HCl were used to distinguish between the roles of cadmium and chlorine in the process. Finally, ZnCl₂ was employed as an alternative to CdCl₂. We report on the efficacy of using these alternative Cl-containing compounds to remove the high density of planar defects present in untreated CdTe. - Highlights: • Cadmium chloride (CdCl₂) activation treatment • Alternative chlorine containing compounds • Microstructure analysis and electrical performances