Binary stacked In2Se3/CuSe precursors were prepared onto substrates with different types of sodium (Na) sources, i.e., soda-lime glass (SLG), sodium-free glass (SFG), SFG with Na-doped Mo layers (Mo:Na), in a co-evaporation system. SIMS depth profiles for In2Se3 precursors deposited at 400 degrees C demonstrated that the different amounts of Na diffused out of each Na source. High-temperature XRD experiments revealed that there was no significant effect of Na on the reaction path of CuInSe2 formation from In2Se3/CuSe stacked precursor. The reaction rate of the precursor without Na (i.e.. SFG/Mo/In2Se3/CuSe) was found to be higher than that of those with Na (i.e., SLG/Mo/In2Se3/CuSe and SFG/Mo:Na(750 nm)/Mo/In2Se3/CuSe). (C) 2011 Elsevier B.V. All rights reserved.