CdS/CdTe solar cells. Part 1: Solar cells processed by the technique of gradient recrystallization and growth

In this paper we present the processing and characterization of thin film C dS/CdTe solar cells obtained by the gradient recrystallization and growth t echnique, GREG. The cells were deposited on soda-lime LOF(TM) conducting gl ass substrates and Cu-Au contacts were evaporated on top of the CdTe film. The films deposition conditions were: for CdS the source temperature T-f va ried between 750 degrees C and 800 degrees C and the substrate temperature T-s varied between 480 degrees C and 550 degrees C, while for CdTe T-f vari ed between 570 degrees C and 650 degrees C and T-s from 460 degrees C to 48 0 degrees C; both films were deposited under a constant Ar gas pressure. Th e films were characterized by X-ray diffraction, atomic force microscopy, o ptical absorption and photoluminiscence. Both CdS and CdTe films were polyc rystalline with preferential orientation in the [002] direction for CdS and in the [111] direction for CdTe; the grain size ranges for the films were 0.2-1 mu m for CdS and 0.5-5 mu m for CdTe. The solar cell photoconductive parameters were determined yielding the best cell performance values of V-O C = 0.7 V, J(SC) = 31 mA/cm(2), ff = 50%, SQE(max) = 0.6 electr./photon at 550 nm and 8% solar energy conversion efficiency.