A one-step method based on solution-processing has been adopted for preparing CH3NH3PbI3 perovskite thin films. The role of chlorobenzene (CB) in film crystallization and the effect of subsequent thermal treatments on material properties has been investigated by performing a comparative study of solar cells developed with three groups of films processed differently. The use of CB promotes the formation of homogeneous films. Heat treatments at low temperature promote grain growth and agglomerations leading to decrease in surface roughness and the removal of chlorobenzene traces present in the film, which in turn leads to the improvement of the interface between the gold contact and perovskite layer. The cell parameters such as V-oc, J(sc) and solar-to-electric conversion efficiency of devices made with heat treated films are found to improve by 11%, 5% and 16% respectively with respect devices made from unannealed films. (C) 2016 Elsevier B.V. All rights reserved.