Impact of a binary Ga2Se3 precursor on ternary CuGaSe2 thin-film and solar cell device properties

CuGaSe2 (CGS) thin-films grown by the three-stage coevaporation process using various Se-fluxes during each growth stage exhibited distinctive properties different from those grown with a constant Se-flux during all three stages. CGS grain size, growth orientation, and the depletion width in solar cell devices were found to depend strongly on the Ga2Se3 precursor formed during the first stage, whereas photo-absorption spectra and device parameters were largely determined by the Se-flux used during the second and third stages when the CGS film near-surface region was formed. A certified efficiency exceeding 10% demonstrated for a ternary CGS solar cell is also reported.