Cu(In1-xGax)Se-2 (CIGS) thin film have been fabricated by a 2-step process using Cu-In-Ga precursors and H2Se gas. A high temperature selenization and in situ annealing process was developed to improve the optoelectronic quality and increase the band gap at the surface of the CIGS absorber. Characterization with SEM and XRD showed the films had large grain size and improved crystallinity. SIMS and PL analysis showed the Ga content at the surface of the absorber was increased and the band gap was higher. Completed solar cells showed V-oc increase resulted from more than one order of magnitude decrease in the saturation current compared to cells selenized at lower temperature. A high V-oc of 623 mV was achieved and the best cell had conversion efficiency exceeding 15%. (C) 2012 Elsevier Ltd. All rights reserved.