Improved performance of perovskite solar cell by controlling CH3NH3PbI3-xClx film morphology with CH3NH3Cl-assisted method

Sequential deposition solution-based method has been widely used for the fabrication of perovskite solar cells (PSCs). However, there is still a challenge to achieve homogeneous and consecutive surface of the perovskite layers. In this work, CH3NH3PbI3-xClx layers were prepared by a modified two-step solution method. Specifically, the optimum amount of CH3NH3Cl pre-added into PbI2 precursor solution, the appropriate size of pinholes and voids appear in PbI2 films and leave room for the growth of CH3NH3PbI3-xClx crystal. Under this condition, the crystal grains size is diminished and the surface coverage ratio of CH3NH3PbI3-xClx film is enhanced, which prevent the combination of electron-hole pairs on the interface between perovskite layer and TiO2 substrate. By varying the CH3NH3Cl amounts, the PSC devices displayed the highest power conversion efficiency of 13 %, which was obviously higher than that of the one prepared via transitional routes (10.32 %). As a result, we developed a simple and repeatable route for controllable synthesis of perovskite absorption layers, which is demonstrated to be effective to improve the performance of PSCs.