Characterization of non-vacuum CuInxGa1 − xSe2 thin films prepared by low-cost sequential electrodeposition technique

Abstract

Copper indium gallium diselenide (CuInxGa1 - Se-x(2)) thin films were grown on indiumtin oxide coated glass substrate by a sequential electrodeposition technique. The deposition bath consisted of an aqueous solution of 10 mM CuCl2, 10 mM InCl3, 20 mM GaCl3, 20 mM H2SeO3 as precursors, and 200 mM LiCl. The pH of the solution was adjusted to 1.7 by adding HCl. Cu, In, Cu, Ga, Cu, Se components were deposited sequentially. Cu/In/Cu/Ga/Cu/Se stacked layers were annealed at 250, 350, 450 and 550 degrees C for 30 min. X-ray diffraction (XRD) studies showed the produced CIGS thin films had polycrystalline structure. From scanning electron microscopy studies, it was found that CIGS thin films exhibited different surface appearances depending on annealing temperature. Energy dispersive x-rays analysis showed that elemental ratio of Se decreased from 46.99 to 14.84 (%) with increasing of annealing temperature. Optical band gap of the CIGS films varied between 1.41 and 2.19 eV. Thicknesses and refractive indices of the produced CIGS thin films were calculated by fitting spectroscopic ellipsometric data (psi and triangle) by using Cauchy model. Deposited CIGS thin films were p-type semiconductor with carrier concentration of -10(16) cm(-3).