Electrical transport properties of TiO₂/MAPbI₃ and SnO₂/MAPbI₃ heterojunction interfaces under high pressure

The electrical transport properties of SnO₂(TiO₂)/MAPbI₃ (MA = CH₃NH₃ ⁺) heterojunction interfaces are investigated from ambient pressure to 20 GPa, and the transport properties are calculated by physical parameters such as trap energy density, binding energy, and charge transfer driving force and defect. Based on the partial density of states (PDOS) of the SnO₂/MAPbI₃ heterojunction interface MAI-termination and PbI₂-termination, greater charge transfer driving force and higher binding energy are observed, obviously showing the SnO₂-based heterojunction is more stable. The SnO₂/MAPbI₃ heterojunction interface possesses stronger electrical transport ability and is less prone to capture electrons compared with the TiO₂/MAPbI₃ heterojunction interface. The differential charge density spectrum shows that the density is lower in the trap energy level of SnO₂/MAPbI₃, whilst the effect of the charge transfer defect is weaker owing to the trap energy level only existing in SnO₂. The SnO₂/MAPbI₃ heterostructure interface is less prone to capture electrons. The greater electron concentration difference is attributed to oxygen vacancy (Vo₀) in the SnO-like environment, resulting in superior electron transport ability compared with the TiO-like environment.