Homologous Bromides Passivation of CH ₃NH ₃PbBr ₃ Single Crystals for Photodetectors with Improved Properties

Abstract

Organic hybrid perovskite single crystal CH₃NH₃PbBr₃ (MAPbBr₃) is popular in the field of photoelectric detection because of its excellent photoelectric properties, but its performance is seriously limited by the surface defects. Here, we report a surface passivation method to effectively reduce the surface defects by immersing MAPbBr₃ single crystal in isopropanol (IPA) solution of CH₃NH₃Br (MABr). Compared to the untreated SC, the photoluminescence intensity of the homologous MABr treated SC is greatly improved by passivation treatment, and the photogenerated carrier lifetime increases from 16 ns to 148 ns. The space charge limited current (SCLC) results show that the trap state density is significantly reduced from 2.34×10⁹ cm^-3 to 7.22×10⁸ cm^-3. The X-ray photoelectron spectrum (XPS) of the Pb element presents an obviously reduced peak of metallized Pb, suggesting that the metallized Pb ion defects at the surface are effectively passivated. The asymmetry in current-voltage (I-V) curves arising from ion migration is substantially compressed. Furthermore, the photocurrent is significantly enhanced, and the responsivity and detectivity are ~ 7 times higher than those of the untreated single crystal device. The results suggest a novel, feasible and efficient strategy to passivate surface defects for perovskite single crystals with improved properties.

Keywords: Perovskite, MAPbBr3 Single Crystal, Surface Passivation, Homologous Bromides, Photodetector