Photogenerated Carriers Surviving for Milliseconds in Perovskites under the Protection of Shallow Trap States.

The performance of perovskite-based photovoltaic and light-emitting devices is susceptive to the interaction between charge carriers and trap states. The inherent trap state tolerance endows perovskite with a series of unprecedented properties; however, the underlying mechanisms remain poorly explored. Herein, we show, with a novel time-resolved stimulated emission spectroscopy approach, that photogenerated carriers are effectively prevented from internal nonradiative recombination and external luminescence quenching by shallow trap states. The photogenerated carriers survive for a period of >3 ms, 4 orders of magnitude longer than the submicrosecond photoluminescence lifetime. The surprisingly long-lived charge carriers can be quantitatively accounted for by a proposed model of trap state-assisted carrier protection (TSACP), which is consolidated by the results of confirmatory experiments on perovskites with varying chemical compositions and micronano structures. These findings shed light on the mechanism of carrier-trap state interaction, which will benefit for more effective defect engineering of perovskite materials and devices.