All-Optical Switching Based on Sub-Bandgap Photo-Activation of Charge Trapping in Metal Halide Perovskites.

Controllable optical properties are crucial for the application of light-emitting materials in optical devices. In this work, controllable photoluminescence in metal halide perovskite crystals was realized via photoactivation of their defects. We found that under continuous excitation, the photoluminescence intensity of a CH 3 NH 3 PbBr 3 crystal can be fully controlled by sub-bandgap energy photon illumination. Such optically controllable emission behavior is rather general as it was observed also in CsPbBr 3 and other perovskite materials. We assign the switching mechanism to reversible light-induced activation/deactivation of nonradiative recombination centers, the presence of which relates to an excess of Pb during perovskite synthesis. Given the success of perovskites in photovoltaics and optoelectronics, we believe that the discovery of green luminescence controlled by red illumination will extend the application scope of perovskites toward optical devices and intelligent control. This article is protected by copyright. All rights reserved.