Molybdenum Nitride Films in the Back Contact Structure of Flexible Substrate Cadmium Telluride Solar Cells

CdTe solar cells in the superstrate configuration have achieved record efficiencies of 16% but those in the substrate configuration have reached efficiencies of only 7.8%. A major reason for the lower efficiency of substrate CdTe solar cells is the poor back contact. In this work, CdTe solar cells of the substrate configuration have been fabricated on flexible metallic substrates. For this type of devices, impurity diffusion out of stainless-steel substrates due to high temperature processing can be a cause for poor cell performance. It is necessary to investigate ways of improving the back contact by trying to mitigate the above factors. In this work, Nitrogen has been incorporated in Molybdenum by RF magnetron sputtering. Nitrogen incorporation has helped achieve a 2% increase in efficiency for the best cell and an improvement of 1.5% on an average.