Robust salt-shelled metal halide for highly efficient photoluminescence and wearable real-time human motion perception

All-inorganic metal halide perovskites (MHPs) with the formula CsPbX3 (X = Cl-, Br-, I-) have excellent photo-physical properties and low-cost fabrication, offering exciting opportunities for flexible electronics. However, the suboptimal quantum yield and inferior stability of solid-state MHPs impede their diverse wearable applications. Here, a straightforward water evaporation crystallization strategy for the preparation of salt-shelled metal halide solids is proposed. The well-designed CsPbBr3@KBr material exhibits narrow green photoluminescence (full-width at half-maximum similar to 20 nm), high quantum yield (87.3 %), and favourable light irradiation and thermal stability. Thus, their applications in waterborne transparency inks and flexible photoluminescent films are demonstrated. Especially, they can be employed as fillers of polyvinyl alcohol (PVA) for high-performance positive friction materials in triboelectric nanogenerators (TENGs), and the output performance of the TENG is 2.3 times higher than the pristine one. As a proof-of-concept, a wearable photoluminescent sensor with a voltage response range of 0-100 kPa and a response time of 125 ms is constructed, which can potentially be served as a passive sensor-in-screen configuration to detect motions of various parts of the human body. It is believed that such metal halides will unleash the possibility of a broad variety of applications in lightweight and multifunctional wearable electronics.