The relatively small band gap values (~1 eV) of CuInSe₂thin films limit the conversion efficiencies of completed CuInSe₂/CdS/ZnO solar cell devices. In the case of traditional two-stage growth techniques, limited success has been achieved to homogeneously increase the band gap by substituting indium with gallium. In this study, thermal evaporation of InSe/Cu/Gase precursors was exposed to an elemental Se vapour under defined conditions. This technique produced large-grained, single-phase Cu(In,Ga)Se₂thin films with a high degree of in-depth compositional uniformity. The selenization temperature, ramp time, reaction period, and the effusion cell temperature with respect to the Cu(In,Ga)Se₂films were optimized in this study. The homogeneous incorporation of Ga into CuInSe₂led to a systematic shift in the lattice spacing parameters and band gap of the absorber films. Under optimized conditions, gallium in cooperation resulted only in a marginal decrease in the grain size, X-ray diffraction studies confirmed single-phase Cu(In,Ga)Se₂material, and X-ray photoluminescence spectroscopy in-depth profiling revealed a uniform distribution of the elements through the entire depth of the alloy. From these studies optimum selenization conditions were determined for the deposition of homogeneous Cu(In,Ga)Se₂thin films with optimum band gap values between 1.01 and 1.21 eV.