CVD of CuGaSe2 for thin film solar cells employing two binary sources

A novel halogen supported chemical vapor phase technique in an open tube system has been employed for the deposition of the polycrystalline thin film CuGaSe2 (CGS). Cu2Se and Ga2Se3 powders served as the source materials and were shown to volatilize stoichiometrically using I-2/H-2 and HCI/H-2, respectively. Different Cu-(g)/Ga-(g) ratios in the gas phase - in the 1/100 to 1/3 range - were studied to determine phase behavior during deposition onto plain and Mo-coated glass substrates at T-sub = 500 degreesC. For single phase CGS material. X-ray diffraction measurements revealed a decrease in the c/a-ratio from 1.963 to 1.957 with increasing Cu-content. In addition, AAS and EDX analysis showed a correlation between Cu-(g)/Ga-(g) and film stoichiometry allowing for the deposition of films with varying Cu/Ga-ratios. Mo/CuGaSe2/CdS/ZnO devices fabricated from CGS deposited at Cu-(g)/Ga-(g) = 1/10 resulted in V-oc, values of up to 853 mV (AM 1.5) which compares favorably to the best values reached for this absorber material so far. (C) 2001 Elsevier Science B.V. All rights reserved.