Solar cells were prepared by depositing CdTe films onto CdS/SnO2/glass substrates in metalorganic chemical vapor deposition ambients with Te/Cd mole ratios which ranged from 0.02 to 15. It was found that the short-circuit current density exhibited a minimum at a Te/Cd ratio of 0.1. The open-circuit voltage was highest for a Te-rich growth ambient, and was appreciably lower for stoichiometric and Cd-rich growth conditions. This resulted in the highest cell efficiency (12%) for Te-rich CdTe films. Auger electron spectroscopy revealed the occurrence of a large amount of atomic interdiffusion at the CdS/CdTe interface when the CdTe films were grown under Te-rich conditions. Tunnelling and recombination observations suggested that the enhanced interdiffusion reduced the interface states, due to stress reduction or to a gradual transition from CdS to CdTe.

H.C.Chou, A.Rohatgi: Journal of Electronic Materials, 1994, 23[1], 31-7