Photoprotection in metal halide perovskites by ionic defect formation

Photoprotection is a vital phenomenon in plants that, under intense and prolonged exposure to light, temporarily limits photon absorption to avoid radiation damage, which allows long-term stable and efficient photosynthesis. Photoprotection has only been linked to organisms; however, we discover a parallel mechanism in metal halide perovskite semiconductors. When perovskite films are exposed to light, a process involving the formation of defects is initiated, which protects the film from overheating and degradation. Defect formation in perovskites is generally undesired, as it leads to a loss of optoelectronic performance. We not only argue that this efficiency loss is temporary but also that it is in fact critical for long-term photostability. Perovskites retain material integrity under intense flux, as defects easily form and the lattice can sustain a large concentration of them. Thus, whether defect formation in perovskites should be mitigated or preserved is a topic requiring further consideration.