First-principles study on the lattice plane and termination dependence of the electronic properties of the NiO/CH3NH3PbI3 interfaces

Abstract

Interpretations of the properties of device interfaces are critical for device design and optimization. Nickel oxides are used as the hole transporting layer (HTL) for organometal halide perovskite (OHP) based solar cells. Here, we performed density functional theory (DFT) calculations combined with non-equilibrium Green's function (NEGF) calculations on the NiO/CH₃NH₃PbI₃ (MAPbI₃) interface. We provide atomistic insight into the structure–property relationship of this NiO/OHP interface. The bulk (e.g., electronic structure) and device (e.g., photocurrent) properties were investigated. The interfacial band alignment is found to be strongly dependent on the lattice plane and the termination of MAPbI₃ due to the interfacial interactions. The increasing strength of interfacial interactions could decrease the valence band offset and increase the conduction band offset between NiO and MAPbI₃, which is beneficial for hole transporting and electron blocking. The device calculations (photocurrent density (J) at different bias voltage (V)) further suggest that the device performance could be improved by selecting the (001) lattice plane of MAPbI₃ and PbI₂-termination. The NiO(100)/MAPbI₃(001)-PbI₂ interface shows the best short circuit current density (J_sc) and open circuit voltage (V_oc) among the studied interfaces. This is possibly due to the largest potential drop at the interface and excellent hole (electron) transmission through NiO (MAPbI₃). Our calculations here may provide a useful interpretation of the role of the PbI₂ layer in charge separation and transport and could contribute to new strategies for interface optimization.