Beneficial Role of Organolead Halide Perovskite CH 3 NH 3 PbI 3 /SnO 2 Interface: Theoretical and Experimental Study

Understanding the interfacial properties of perovskite/SnO 2 interface is important for perovskite solar cell design and optimization. Here, interfacial structure and transport properties of CH 3 NH 3 PbI 3 /SnO 2 interfaces are investigated comprehensively by density functional theory and experiment. Forming CH 3 NH 3 PbI 3 /SnO 2 interfaces weakens the gap states induced by CH 3 NH 3 PbI 3 surfaces. The interfacial transport properties are strongly dependent on the interface atomic configurations. The CH 3 NH 3 PbI 3 /SnO 2 interface with PbI and O terminations is more beneficial for hole blocking and electron transporting due to the largest valence band offset compared to the CH 3 NH 3 PbI 3 /SnO 2 interface with other terminations. Moreover, it exhibits a larger electrostatic potential difference compared with CH 3 NH 3 PbI 3 /TiO 2 interface, leading to the higher electron transfer efficiency. Hence, higher power conversion efficiency is achieved based on CH 3 NH 3 PbI 3 /SnO 2 compared to CH 3 NH 3 PbI 3 /TiO 2 structure in experiments. In addition, CH 3 NH 3 PbI 3 /SnO 2 interfaces with PbI terminations are more stable than those with CH 3 NH 3 I terminations, suggesting PbI 2 layer may be preferentially formed on SnO 2 substrate during CH 3 NH 3 PbI 3 fabrication process. Such results could provide a useful understanding on CH 3 NH 3 PbI 3 /SnO 2 interface and contribute to new strategies for the interface optimization.