Improving the interfacial contact between CH3NH3PbI3-xClx and Au by LiTFSI solution treatment for efficient photoelectric devices

Organic lead halide compounds with perovskite structure become a promising photovoltaic material for low-cost thin film solar cells in recent years. The property of perovskite/metal interface is a fundamental topic for the effective charge transfer at metal electrodes. In this work, we develop an interface modification method of lithium bis(trifluoromethane sulfonimide) (LiTFSI) solution treatment, which can effectively decrease the charge transfer resistance at the CH3NH3PbI3-xClx/Au interface. After the solution treatment, uniform nanodots are formed at the surface of CH3NH3PbI3-xClx films, and the barrier height at CH3NH3PbI3-xCIx/Au interface reduces from 0.51 V to 0.08 V. As a consequence, the efficiency of hole conductor free solar cells with CH3NH3PbI3-xClx harvester increase from 4.0% to 7.6% under one sun condition. It is also found that the hole conductor free perovskite solar cell can work in a photodetector mode, which has the same output properties with phototransistors. After the LiTFSI solution treatment, the sensitivity of this photodetector can be improved for about one time. (C) 2015 Science Press and Dalian Institute of Chemical Physics. All rights reserved.