Polycrystalline thin film CdTe continues to be a leading material for the development of cost effective and reliable photovoltaics. Thin film CdTe solar cells and modules are typically heterojunctions with US being the n-type partner, or window layer. The preferred configuration for CdTe solar cells is the superstrate structure. The cadmium chloride heat treatment, the back contact formation process, and the utilization of resistive, buffer layers in tandem with a thin cadmium sulfide window layer, are important areas of research in thin film CdTe solar cells. This paper reviews work on CdTe thin film solar cells sponsored by the National Renewable Energy Laboratory. Results for a vapor chloride heat treatment with high throughput characteristics, a dry back contact process, and a comparative study of resistive buffer layers and their effect on the performance of CdTe solar cells are presented. (C) 2004 Published by Elsevier Ltd.