ELECTRODEPOSITION AND HEAT-TREATMENT OF CUINSE2 FILMS

Thin polycrystalline CuInSe2 films to be employed in solar cells have been prepared by electrodeposition on a titanium substrate. n-type films were obtained by thoroughly controlling the bath composition (an aqueous solution containing CuCl2, InCl3 and SeO2, pH around 1.5) and the operating conditions. These films were then submitted to heat treatment at temperatures up to about 500 °C both in an O2- and in an H2-containing atmosphere. The as-grown and treated samples were examined by X-ray diffraction, electron microprobe analysis and scanning electron microscopy. Hot probe analyses and resistivity measurements were also performed. The results obtained provided evidence that the quality of the films improves as a result of heat treatments and, in particular, that the mean crystallite size increases. X-ray investigation showed the films to have a high degree of (111)F, (112)U preferred orientation and to contain small quantities of binary phases, possibly indium selenides, which were oxidized at temperatures above 300 °C. Furthermore, macroscopic oxidation of the CuInSe2 films to In2O3 was detected at the highest temperature in the O2-containing atmosphere. © 1990.