Fabrication of CuIn(Ga)Se2 Thin Films by Electrochemical Deposition with Additive

Abstract

CuIn(Ga)Se2 (CIGS) thin films were fabricated by electrochemical deposition method in a single bath in which ionized Cu, In, Ga, and Se were contained. The electrolyte was prepared by dissolving CuCl2, InCl3, GaCl3, H2SeO3, and LiCl (as pH adjuster) in deionized water. To modify the surface and microstructures of CIGS films, various amounts of gelatin were added in the solution. Potentiostatic deposition process was achieved by applying a voltage ranging from −640 to −1100 mV vs. Ag/AgCl. We prepared two different types of electrolyte baths for electrochemical deposition. All experiments were conducted at room temperature, and pH was adjusted about 2. As-deposited films were then annealed at 500°C in Ar for crystallization. Microstructures of fabricated CIGS films were observed by field emission scanning electron microscope. Crystallographic information was analyzed by high resolution X-ray diffractometer. The use of gelatin helped in fabricating crack-free CIGS thin films with greatly improved surface morphology. The improved morphological conditions resulting from grain refinement affected the structure of the post-annealed film as well. XRD data revealed that addition of excess gelatin causes fading of some of the CIGS peaks.