Reducing ion migration in methylammonium lead tri-bromide single crystal via lead sulfate passivation

Surface passivation of organic-inorganic halide perovskites (OIHPs) is a crucial step to annihilate the surface defects and to control the deteriorated ion migration phenomenon. Here, we study the role of lead sulfate (PbSO4) as an effective passivator in OIHP single crystals (SCs). Using impedance spectroscopy, we evaluate the ion migration and electrical properties of lead sulfate-passivated methylammonium lead tri-bromide (MAPbBr(3)) SCs. We found that the low-frequency impedance response that is assigned to the ionic motion in the MAPbBr(3) SC is strongly affected by the inorganic PbSO4 surface treatment. The activation energy corresponding to the ion migration of MAPbBr(3) SC is increased from 0.28 to 0.36eV after PbSO4 surface treatment. The temperature-dependent I-V hysteresis of the MAPbBr(3) SCs upon PbSO4 passivation was also measured. We found that such PbSO4 surface treatment stabilizes the crystal surface and improves the hysteresis properties of the crystals at elevated temperatures.