CuInSe2 (CISe) with a bandgap of 1.0 eV is the appropriate bottom layer material for the multi junction solar cell. CISe thin films have been prepared using the three-stage process, in which the substrate temperature (T-s) of the second and the third stage was varied from 490 to 580 degrees C. The preferred orientation of the CISe film changed from (112) to (220) as the Ts was increased from 490 degrees C to onward. CISe films had large and columnar grains at all values of T-s, but surface became increasingly smoother as the T-s was increased from 490 to 580 degrees C. Secondary ion mass spectrometry analysis revealed that Cd diffusion from CdS buffer layer to CISe layer was more when the preferred orientation was (220), which helped in the formation of homojunction inside CISe. Open circuit voltage increased upon increasing the T-s due to the increase in the Na concentration inside CISe. The conversion efficiency of the solar cells increased from 8.80 to 12.64% when the Ts was raised from 490 to 580 degrees C. (C) 2017 Published by Elsevier B.V.