Polycrystalline CuIn1-xGaxSe2(0 ≤ x < 0.3) films (CIGS) were deposited by coevaporating the elements from appropriate sources onto glass substrates (substrate temperature ∼ 720 to 820 K). Photoconductivity of the polycrystalline CIGS films with partially depleted grains were studied in the temperature range 130-285 K at various illumination levels (0-100 mW/cm2). The data at low temperature (T < 170 K) were analyzed by the grain boundary trapping model with monovalent trapping states. The grain boundary barrier height in the dark and under illumination were obtained for different x-values of CuIn1-xGaxSe2films. Addition of Ga in the polycrystalline films resulted in a significant decrease in the barrier height. Variation of the barrier height with incident intensity indicated a complex recombination mechanism to be effective in the CIGS films.
Chakrabarti, R., Maiti, B., Chaudhuri, S., & Pal, A. K. (1996). Photoconductivity of Cu(In, Ga) Se2films. Solar Energy Materials and Solar Cells, 43(3), 237–247. https://doi.org/10.1016/0927-0248(95)00174-3