Differences between CuGa/In and Cu/Ga/In films for selenization

CuGa/In and Cu/Ga/In metal precursor films were deposited by co-evaporation and selenized in situ. Differences were studied by XRF, GIXRD, SEM, EPMA, and SIMS for precursors, partially selenized, and completely selenized films. Solar cells were fabricated from completely selenized absorber films, and were characterized by JV and QE measurements. More intermixing of Cu and Ga was exhibited by CuGa/In, relative to Cu/Ga/In precursors. This caused a lower Ga/(Ga+In) composition near the surface, which led to higher current, lower voltage, and worse photovoltaic performance for CuGa/In. The difference in relative selenization kinetics of Ga and In were not responsible for the evolution of the contrasting Ga/(Ga+In) profiles.