Impacts of the Electron Transport Layer Surface Reconstruction on the Buried Interface in Perovskite Optoelectronic Devices.

Using density functional theory combined with ab initio molecular dynamics, we comprehensively investigated the performance enhancement mechanism of the device after surface reconstruction by passivating different halogen groups (i.e., F or Cl) at the ETL/perovskite interface. We demonstrated that the halogen group at the ETL layer could stabilize the geometric structure of the perovskite surface by balancing the interfacial interaction, ionic migration, and lead iodide framework. Even though halogen passivation decreased and increased the interface charge transfer at the O- and SnO-terminated MAPbI3/SnO2 interfaces, respectively, halogen passivation optimized surface reconstruction and could theoretically relieve the interface carrier recombination according to the changes in conduction band offsets generated by halogen passivation. Furthermore, the interfacial carrier recombination of the MAPbI3/SnO2 interface was also connected to the interfacial gap states, which were smaller for O-terminated MAPbI3/SnO2 interfaces with halogen passivation-induced surface reconstruction but larger for the SnO-terminated cases. Hence, our findings have implications for the design of buried interface optimization in perovskite optoelectronic devices.