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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.