PHOTOCONDUCTIVITY OF CU(IN,GA)SE-2 FILMS

Polycrystalline CuIn1-xGaxSe2 (0 less than or equal to x < 0.3) films (CIGS) were deposited by coevaporating the elements from appropriate s ources onto glass substrates (substrate temperature similar to 720 to 820 K). Photoconductivity of the polycrystalline CIGS films with parti ally depleted grains were studied in the temperature range 130-285 K a t various illumination levels (0-100 mW/cm(2)). The data at low temper ature (T < 170 K) were analyzed by the grain boundary trapping model w ith monovalent trapping states. The grain boundary barrier height in t he dark and under illumination were obtained for different x-values of CuIn1-xGaxSe2 films. Addition of Ga in the polycrystalline films resu lted in a significant decrease in the barrier height. Variation of the barrier height with incident intensity indicated a complex recombinat ion mechanism to be effective in the CIGS films.