The influence of precursor stack structure on the formation of CuInSe2 (CIS) thin films was investigated by structure characterization of samples with single and multiple InSe/CuSe bilayer stacks deposited by co-evaporation on Mo/glass substrates. With an increase in the number of stacks, the temperature for complete grain growth decreased, but the grain size in the resulting CIS thin films was small. The low crystallization temperature could be attributed to the low activation energy for nucleation, which in turn afforded a nanocrystalline CIS phase even during low-temperature evaporation. Because of the large grain size (1.3 mu m) in the resulting CIS film and low crystallization temperature, the precursor structure with two alternating InSe/CuSe stacks was concluded to be optimal for solar cell applications; such a structure would have the appropriate number of nucleation sites for complete CIS crystallization to afford a large grain size. (c) 2013 Elsevier B.V. All rights reserved.