First-principles Study of Back Contact Effects on CdTe Thin Film Solar Cells

Forming a chemically stable low-resistance back contact for CdTe thin film solar cells is critically important to the cell performance. This paper reports theoretical study of the effects of the back contact material, Sb2Te3, on the performance of the CdTe solar cells. First-principles calculations show that Sb impurities in p-type CdTe are donors and can diffuse with low diffusion barrier. There properties are clearly detrimental to the solar cell performance. The Sb segregation into the grain boundaries may be required to explain the good efficiencies for the CdTe solar cells with Sb2Te3 back contacts.