The effect of surface preparation on properties of cadmium telluride thin film heterojunctions

The effects of surface preparation on CdTe-based thin film heterojunctions have been investigated through characterisation of ITO/p-CdTe and CdS/p-CdTe solar cells. The surface treatment methods include air exposure at laboratory temperature for several months, heat treatment, bromine-in-methanol etching, and bromine-in-methanol etching with subsequent hydrogen heat treatment. The authors have found that the behaviour of CdTe heterojunctions was significantly improved by the surface treatment of CdTe films exposed to air for several months at laboratory temperature prior to window material deposition. The stability of as-prepared cells has been considerably enhanced. Other methods of surface treatment seem to have insignificant effects on the improvement of subsequent heterojunctions. The explanations given for the improved performance of the solar cells are discussed.