Thin film CdTe solar cells

Abstract

This paper reviews some of the most promising CdTe-based solar cells, with efficiencies in excess of 10%, prepared by various film deposition methods including close-spaced vapor transport, close-spaced sublimation, hot-wall vacuum evaporation, electrodeposition and screen-printing. One of the major problems with CdTe films has always been the difficulty of achieving high p-type doping in order to provide a low resistance frontal layer as well as to solve the ohmic contact problem through tunneling effects in a Schottky-barrier contact. Heavily p-type doping experiments with phosphorus and arsenic impurities are described. The results of the diffusion treatment on homoepitaxial CdTe films, grown by the close-spaced vapor transport method are investigated by measuring the concentration and profile of the impurities, and by analyzing the excitation spectra of luminescence at 1.8 K; it is shown that the doping efficiency is related to the structural location and the electronic activity of the impurity.