In Situ Embedding Synthesis of Highly Stable CsPbBr3/CsPb2Br5@PbBr(OH) Nano/Microspheres through Water Assisted Strategy

The disappointing stability of perovskites, especially in water, remains a key issue hindering their further commercialization. Here, CsPbBr3/CsPb2Br5@PbBr(OH) (PQDs@PbBr(OH)) nano/microspheres with superior stability and outstanding photoluminescence quantum yield (PLQY, approximate to 98%) are fabricated through a water-assisted process. The nano/microspheres can maintain excellent photoluminescence (PL) intensity and high PLQY (approximate to 90%) when immersed in water for more than 18 months. By changing the water content in the reaction mixture, the phase, particle size, and PL peaks of the nano/microspheres will change. Compared with CsPbBr3/Cs4PbBr6 nanocrystals synthesized without water, PQDs@PbBr(OH) nano/microspheres exhibit better thermal stability, photostability, and superior stability in water. Based on the first-principles calculations, the enhanced stability results from PbBr(OH) with high decomposition enthalpy in water, which can effectively prevent water from contacting PQDs embedded in it. Moreover, white light-emitting diodes are fabricated by mixing green-emitting PQDs@PbBr(OH) powder and K2SiF6:Mn4+ (KSF) red phosphor on a 460 nm blue chip and the device shows a high luminous efficacy of 101.27 lm W-1 at 10 mA. This work not only provides a reliable method for the facile preparation of ultrastable perovskites, but also has great potentials for future practical applications.