Water-driven CsPbBr₃ nanocrystals and poly(methyl methacrylate)-CsPbBr₃ nanocrystal films with bending-endurable photoluminescence

Perovskite nanocrystals are regarded as next-generation functional materials for display applications, especially for flexible liquid crystal displays (LCDs). As a potential component of flexible LCD backlights, perovskite nanocrystal films are facing a challenge issue of deformation-induced shift of photoluminescence, leading to an image distortion. To date, most synthesis methods have involved the use of organic solvent in precursor solutions, such as N,N-dimethylformamide and dimethyl sulfoxide, which poses a potential threat to the environment, health and security. In this work, we demonstrate the feasibility to produce microsized CsPbBr₃ crystals with deionized water as the precursor solvent via an environmental-friendly and cost-efficient approach and CsPbBr₃ nanocrystals with green (~522 nm) and blue (~493 nm) emissions from the microsized CsPbBr₃ crystals in toluene under sonication. The blue-emitting nanocrystals exhibit a photoluminescence (PL) quantum yield of 80%, much larger than 61.4% of the CsPbBr₃ nanocrystals made by an anti-solvent method; the green-emitting nanocrystals exhibit better stability than those made by the antisolvent method over 9 days. Using the green-emitting CsPbBr₃ nanocrystals, we prepare a bilayer structure with a poly(methyl methacrylate)-CsPbBr₃ nanocrystal film on a polyethylene terephthalate plate. The films exhibit bending-endurable photoluminescence, i.e. the wavelength of the PL peak remains unchanged, for local radius of curvature of the bilayer up to 10.07 mm under bending. This study opens a new avenue to potentially produce microsized perovskite crystals without harmful organic solvents and bending-endurable backlight films for the applications in flexible display.