Compositional engineering of mixed halides is an effective approach to fabricate highly efficient perovskite solar cell. The mixed halide perovskite of MAPbI(3-x)Cl(x) attracts a great of attentions due to its excellent optoelectronic properties. However, the role of chlorine in MAPbI(3-x)Cl(x) is still under discussion by now. Here we introduce PbCl2 as additives into PbI2/DMF solution to study its effects on the formation of MAPbI(3-x)Cl(x) film, which is fabricated from Lewis acid-base adducts through a modified two step method. We demonstrate that the chloride ions have positive roles in fabrication of high quality perovskite MAPbI(3-x)Cl(x) films, characterized by high crystallization, strong grain orientation, large grain size and lower trap densities. Compared to perovskite solar cells without chloride incorporation, the performance of solar cells based on MAPbI(3-x)Cl(x) improves significantly due to its high carrier mobility, efficient carrier transportation and low recombination in device. (c) 2018 Elsevier Ltd. All rights reserved.