Device modeling of CH3NH3PbI3-xClx. based electron transport layer-free planar perovskite solar cells was performed. The simulation was conducted by the program SCAPS (Solar Cell Capacitance Simulator). With appropriate physical parameters, a high open-circuit voltage of 1.04 V close to results reported experimentally was successfully reproduced in the simulation. Simulation results revealed a great de pendence of PCE on the thickness and defect density of the perovskite layer. An optimum perovskite thickness of about 500 nm was confirmed and it well consistent with the thickness range of real devices was derived. Meanwhile, parameters including the FPO/perovskite interface defect density as well as the doping concentration of the front contact (PTO) were identified to significantly influence the performance of the device. In particular, the interface quality at the FPO/perovskite interface has greater impact on the device parameters than that at the perovskite/FITL interface, which suggests that more attention should be paid to the front FTO/perovskite interface to further enhance the performance of electron transport layer-free device. Appropriate interface defect passivation to reduce the interface defect density to the order of similar to 10(15) cm(-3) is necessary and urgently needed. Lastly, the effect of the electron and hole mobility and carrier diffusion length of CH3NH3PbI3-xClx were also analyzed and the results revealed that the mobility and diffusion length experimentally reported (1.0 pm) are large and long enough for high efficiency. (C) 2016 Published by Elsevier B.V.