Thin Film Solar Cells with n-type CdTe Absorber and p-type ZnTe Window Layers
Vasilios Palekis, Wei Wang, Sheikh Tawsif Elahi, Md Zahangir Alom, Chris Ferekides
University of South Florida, Tampa, FL, United States

In this paper the effect of indium (In) doping on CdTe thin film solar cells was investigated. CdTe thin films were deposited using the elemental vapor transport (EVT) technique under various Cd/Te gas phase ratios and In vapor concentrations. Solar cells of the superstrate configuration (glass/TCO/CdS/n-CdTe/p-ZnTe/BC) have been fabricated and characterized. There was a correlation between the concentration of In in the vapor phase and net n-type doping for CdTe devices fabricated near Cd/Te stoichiometric ratio; increasing the amount of indium resulted in higher n-type doping in CdTe. From C-V measurements doping levels >1016cm-3 were achieved. Devices were also fabricated at various Cd/Te vapor ratios. Films deposited at lower Cd/Te vapor ratios (i.e., Te-rich) exhibited higher n-type doping. Lower Cd/Te ratios favor the creation of Cd-vacancies which are needed for substitutional In doping, which can explain why the net doping increases at lower Cd/Te ratios.