Effects of post-deposition CdCl2 annealing on electronic properties of CdTe solar cells

The effects of post-deposition CdCl2 annealing temperature on the electronic properties of CdTe solar cells were investigated. CdTe devices incorporate Mg doped ZnO as a buffer layer and selenization using a CdSe interlayer for reducing the buffer/absorber interface recombination and increasing solar energy absorption respectively. The post-deposition CdCl2 annealing treatments were done under separate, inert atmospheres of nitrogen and helium across the temperature range 380-430 degrees C. Electrical characterization of devices is carried out including temperature dependent current-voltage characteristics, admittance spectroscopy, and Shockley-Read-Hall recombination analysis. The best improvements in device efficiency are obtained upon annealing at temperature 410 degrees C. This anneal correlated with reduced back contact barrier in CdTe and reduced grain-boundary barrier height which is beneficial for enhanced charge transport.