▎ 摘　　要

Functionalized graphene is widely used in various functional devices. Here, we introduce a simple plane capacity model and the density functional theory to investigate the origin of charge transfer in the graphene/CH3NH3PbI3 interface, where graphene can be p-type or n-type doped by combining with different exposed surfaces of CH3NH3PbI3. Our calculations indicate that at the equilibrium distance, the work function of isolated graphene layer should be corrected by adding a value for assessing the charge transfer. After integrating the perovskite film with the functionalized graphene layer, we obtain a van der Waals heterostructure solar cell with a p-i-n configuration, which introduces a built-in electrical field to facilitate the separation and transport of the photogenerated carriers. The new p-i-n junction highlights the interface effect on graphene in solar cell, which offers an avenue to design new photovoltaic devices with high performance.