Bias effect on surface chemical states of CH3NH3PbBr3 hybrid perovskite single crystal: Decreasing CH3NH2 molecular defect

Highlights: • CH₃NH₃PbBr₃ single crystal was biased with 2 and 10 V. • The core-level and valence spectra were obtained by photoelectron spectroscopy with synchrotron radiation. • The total amount of molecular defects, CH₃NH₂ was decreased from 22 to 10%. • It has a high possibility to decrease the defect level at the interface in the hybrid perovskite-based solar cells. A CH₃NH₃PbBr₃ (MAPbBr₃) single crystal was subjected to 2 and 10 V biasing for 10 min under ultra-high vacuum to investigate the bias effect on the surface of MAPbBr₃. Under these controlled conditions, we performed high-resolution photoelectron spectroscopy on the MAPbBr₃ single crystals at photon energies of 460 and 100 eV under synchrotron radiation to obtain core-level and valence structure spectra. The CH₃NH₂ molecular defect relative intensity area ratio decreased from 22% to 10%. It was assumed that the bias effect can induce a low density of defect states to suppress large defect-pinned energy states at the interfaces.