Non-contact measurement of ion mobility in single halide perovskite particles

Halide perovskites, with tunable photovoltaic properties, is one of the most attractive materials in photovoltaics. The non-negligible soft lattice in perovskites induces vacancy-mediated ion migration, which is crucial to the device's efficiency and long-term stability. However, the methodologies to quantify and directly observe ion migration often require the direct contact of a metal electrode with the perovskite materials, where interfacial interactions and interior ion migration are intertwined. Here, we developed a non-contact method to evaluate the ion mobility of MAPbBr₃ via combining PL microscopy and an interpenetrating electrode device. We demonstrated the polarization and recovery dynamics of single MAPbBr₃ particles in an external electric field, as measured by modulation of the optical contrast during switching of the external electric field. The PL intensity was suppressed under the external electric field, which was mainly attributed to the ion migration. And, the PL spectra showed that the blue-shift of MAPbBr₃ originated from lattice distortions induced by field-induced ion migration. Most importantly, we obtained an intrinsic ion mobility for single MAPbBr₃ particles of (2.56 ± 0.67) × 10^-10 cm² V^-1 s^-1 under non-contact conditions.