The formation of ZnTe:Cu and Cu_xTe double layer back contacts for CdTe solar cells

Processes to form a Cu_xTe layer on a ZnTe:Cu layer were investigated by various deposition methods and heat treatment. These were to make ZnTe:Cu/Cu_xTe double layer contacts for CdTe solar cells and to have benefit from both the well-matched interfacial property of ZnTe:Cu and low-resistivity Cu_xTe. The method to form Cu_xTe compounds was annealing the bi-layer of copper and tellurium which were deposited by sputtering. At an adequate annealing condition, Cu_xTe alloy was formed while maintaining underlying ZnTe without intermixing. Cu_xTe was also formed using co-deposition method. However, in terms of crystallinity, the bi-layer deposition method was considered to be better. According to this experiments, ZnTe:Cu/Cu_xTe double layer contact was successfully formed. This double layer contact is expected to be a good candidate for high efficiency CdTe solar cell.