Cyclic voltammogram studies were performed on H2SeO3, CuSO4, In-2(SO4)(3), and GaCl3 of H2SeO3+CuSO4+In-2(SO4)(3) and H2SeO3+CuSO4+In-2(SO4)(3)+GaCl3 to understand the electrodeposition mechanism. The reduction potential from the cyclic voltammogram studies indicates that the first deposited layer is Cu from the Cu-In-Se and Cu-In-Ga-Se (CIGS) solution mixture. The subsequent deposition of the In and Ga layers is more favorable on the first deposited Cu layer. CIGS absorber layers were fabricated using a two-step electrodeposition process. The first layer of Cu-rich CIGS thin film was electrodeposited from CuCl2, InCl3, GaCl3, H2SeO3, and LiCl dissolved in a pH 3 buffer solution, and the subsequent second layer of the In-Se thin film was electrodeposited from a solution mixture of indium sulfate, sulfamic acid, and LiCl. The bilayer electrodeposited films were annealed in a vacuum chamber in Se atmosphere. The as-deposited and annealed films were analyzed by inductively coupled plasma spectrometry, scanning electron micrographs, and X-ray diffraction analysis. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3427514] All rights reserved.