AbstractElectrodeposition (ED) of CuInSe₂-based thin films from a buffered single-bath on dcsputtered Mo layers has been investigated. In order to understand the film growth, cyclic voltammetry (CV) was used to identify mechanisms leading to the formation of CuInSe₂ and Cu(In,Ga)Se₂. Similar CV data were observed for deposition from Cu-Se, Cu-In-Se, Cu-Ga-Se, and Cu-In-Ga-Se baths. A preliminary mechanism for CuInSe₂ and Cu(In,Ga)Se₂ film growth has been proposed from CV, composition and glancing incidence x-ray diffraction (GIXRD) data. Incorporation of In into the growing films occurs via reaction with H2Se, formed by reduction of the initially deposited Cu3Se₂, to form In2Se3, which is in turn rapidly assimilated into the film by reaction with copper selenides to form CuInSe₂. The incorporation of Ga may occur via a similar mechanism, however, the precipitation of Ga(OH)3 can not be ruled out as a possible route for Ga uptake. All as-deposited ED CuInSe₂–based films have poor crystallinity and require annealing in H₂Se prior to device processing. Preliminary device results are presented, reporting a conversion efficiency of 6.5% and 6.2% for electrodeposited CuInSe₂ and Cu(In,Ga)Se₂, respectively.