Study of MoOx Back Contact for Low Temperature CdTe Solar Cells on Superstrate Configuration

Copper is a crucial element for the CdTe doping and consequently for high conversion efficiency. To analyse the effect of copper doping it is necessary to remove it from the back contact in order to avoid uncontrolled copper diffusion in the absorber. Recently, MoO3 has been successfully applied for back contact, because of its work function. In this work we present a study on the effect of MoOx buffer and copper doping on low substrate temperature vacuum evaporated CdTe. Starting from our CdTe baseline with copper/gold back contact (with routine efficiencies above 14 %), solar cells have been prepared with MoOx/Mo and MoOx/Au back contact deposited by reactive radio frequency sputtering. MoOx have been applied with different thicknesses and oxygen contents. On the other hand copper has been deposited on the CdTe surface and diffused by annealing in vacuum, prior to the MoOx/Metal deposition for CdTe doping investigation. With MoOx/Metal back contact and a 0,15