In this paper, a new precursor solution of PbICl is successfully prepared by adding PbCl2 powder into the DMF solution of PbI2 at room temperature with the molar ratio of PbCl2 and PbI2 at 1:1 and demonstrated for efficient planar perovskite solar cell by vapor-assisted solution process for the first time. The results reveal that the solubility of PbCl2 in DMF is dramatically improved by the formation of PbICl and the resulting PbICl thin film with low crystallinity and porous morphology can be easily converted to CH3NH3PbI3-xCLx thin film without any lead halide residuals by the treatment of CH3NH3I vapor at 150 degrees C in air. The planar perovskite solar cells based on the 0.8 M PbICl precursor solution exhibit the highest photovoltaic conversion efficiency of 11.11% along with an open-circuit voltage of 0.93 V, a short-circuit photocurrent density of 17.31 mA cm(-2) and a fill factor of 0.69. (C) 2015 Elsevier B.V. All rights reserved.