The control of native defects in thin-film solar cells was investigated by using a novel source, for close-spaced sublimation, which was prepared by vacuum evaporation. The evaporated Cd and Te sources were prepared on glass substrates at room temperature, and the Cd/Te ratio was controlled by varying the Cd and Te beam equivalent pressures. In cells which used a Te-rich source, the conversion efficiency was less than 0.2% because of an extremely low shunt resistance. A conversion efficiency of more than 15% was obtained by using a Cd-rich source. The capacitance-voltage characteristics revealed that the acceptor concentration in the CdTe layer increased with an increasing Cd/Te ratio in the evaporated source. The photoluminescence spectra implied that the formation of Cd vacancies in the CdTe layer was suppressed by using a Cd-rich source.

Native Defect Control of CdTe Thin Film Solar Cells by Close-Spaced Sublimation. T.Okamoto, S.Kitamoto, A.Yamada, M.Konagai: Japanese Journal of Applied Physics - 1, 2001, 40[5A], 3089-92