Moisture-induced phase transition and emission color change for lead-free manganese (II)-Based halide perovskite crystals with greatly improved photoluminescence quantum yield

Halide perovskites with phase transition-sensitive fluorescence color have attracted great attentions in the field of sensing and detection. Though some achievements have been made, the photoluminescence quantum yield (PLQY) for such materials is usually less than 10% before and after phase transition, which is an intrinsic restriction for their application. Herein, we reported a novel lead-free DMAxMnBrx+2 perovskite crystals with moisture-sensitive emission color as well as high PLQY. The result shows that the octahedral coordination of Mn2+ in DMAMnBr3 gives rise to orange emission around 610 nm with PLQY of 41%. While the tetrahedral coordination of Mn2+ in DMA2MnBr4 causes bright green emission nearby 517 nm with a high PLQY of 70%, which is nearly 10 times higher than that of previously reported results. The in situ formation of DMA+ in solution is the key for the dramatically enhanced PLQY. Moreover, as-prepared orange emitted DMAMnBr3 crystals are sensitive to moisture. Just within several tens of second after exposing in the moisture environment, the original orange emission from DMAMnBr3 will turn to green light emission from DMA2MnBr4. The high PLQY of as-prepared DMAxMnBrx+2 perovskite crystals make them possible to be dispersed into non-luminous matrix at a low concentration for moisture detection.