Chlorine Doped n-Type CdTe Solar Cells

This paper investigated the effect of chlorine (Cl) doping on CdTe thin film solar cells. Polycrystalline CdTe films are grown by the elemental vapor transport (EVT) process with various Cd/Te gas phase ratios and Cl vapor concentrations. Solar cell devices of the configuration glass/TCO/CdS/n-CdTe/p-ZnTe/BC have been fabricated and characterized. Increasing the Cl vapor concentration results in higher n-type doping in CdTe. Films deposited at higher Cd/Te vapor ratios (i.e. under Cd-rich vapor composition) exhibited higher n-type doping. The higher Cd/Te ratios facilitate the creation of Te-vacancies, which are required for substitutional Cl doping, resulting in the net doping increases at higher Cd/Te ratios. Minority carrier lifetimes~ 7 ns have been measured for Cl doped CdTe absorbers by TRPL measurements.