The power conversion efficiency (PCE) of P3HT:PCBM bulk heterojunction solar cells highly depend on the processing conditions of the blend film. Among many factors investigated, the effect of blend solution temperature for spin casting on PCE of solar cells is currently missing in the literature. In this work, we have systematically analyzed the effect of solution casting temperature on solar cell performance of P3HT:PCBM bulk heterojunction layer. We have found that the ideal casting temperature is similar to 60 degrees C for the blends. Further annealing of the blend does not change the surface morphology substantially at the ideal temperature as opposed to the films prepared at other temperatures. (C) 2015 Elsevier B.V. All rights reserved.