Water-driven photoluminescence reversibility in CsPbBr₃/PDMS-PUa composite

Strong ionic character endows all-inorganic perovskite nanocrystals (NCs) with particular optoelectronic features when interacting with common polar solvents, such as water. However, the interaction mechanism of water affecting perovskite NCs is still lack of in-depth understanding. This study systematically explores the roles of water on CsPbBr₃ nanocrystals (CNCs) by finely controlling the polymer coating degree of polydimethylsiloxane-based polyurea (PDMS-PUa). Through this coating, the effect of water on CNCs is found to experience from “fluorescence quenching” owing to irreversible crystal decomposition towards “forward fluorescence reversibility” by crystal destruction and recrystallization. With gradually enhanced coating, a phenomenon of “reverse fluorescence reversibility” is further observed in that water begins to passivate the CNCs’ defect states. Finally, “fluorescent balance” can be achieved with a thick enough coating, where water can hardly contact with the CNCs. Inspired by the fluorescence reversible mechanism discovered, a new wearable intelligent sensing skin is demonstrated by using the CsPbBr₃/PDMS-PUa composite as raw material. Both water contact and humidity change can be perceived through photoluminescence (PL) intensity, corresponding to stimuli-responsive sensory nerves of human skin. It is expected that these findings will shed some new lights on perovskite NCs.