The effect of the CdCl2 treatment on CdTe/CdS thin film solar cells studied using deep level transient spectroscopy

Thin film CdTe/CdS solar cells have been studied using deep level transient spectroscopy. The correlation-deep level transient spectroscopy (DLTS) technique was utilized as conventional analysis methods such as the boxcar-based approach were found to be inadequate under certain experimental conditions. The primary objective was to study the effect of a key processing step in the fabrication of thin film CdTe solar cells, namely the post-deposition heat treatment in the presence of CdCl2. The substrate temperature as well as the ambient used during this process were varied around predetermined conditions for optimum solar cell performance, in order to identify performance-limiting defects, and in general improve understanding of thin film CdTe solar cells. Solar cells without the CdCl2 heat treatment were also fabricated. A series of electron and hole traps were found in the various devices studied, with electron traps being present primarily in solar cells with limited performance. 23 refs.