Conventional furnace selenization process was optimized to achieve effective selenization using diethylselenide (C2H5)(2)Se (DESe). An optimized quantity of Na was added to improve V-oc, FF and morphology. Sputter-deposited CuGa and In metallic precursors were homogenized in an inert atmosphere prior to the introduction of DESe followed by rapidly heating to the maximum process temperature to avoid formation of detrimental binary phases. Selenization was carried out in the temperature range 475-515 degrees C followed by sulfurization in dilute H2S. Solar cells were completed by depositing CdS heterojunction partner layer, i:ZnO/ZnO:Al window-bilayer and metallic contact fingers. PV conversion efficiency of 13.7% with a V-oc of 540 mV, J(sc) of 38.3 mA/cm(2) and FF of 66.3% were obtained on 0.442 cm(2) cell areas. The process can be easily scaled-up for economic large-scale manufacture. (C) 2010 Published by Elsevier B.V.