Interface-directed synthesis of CsPbBr₃-based particles with water-ODE antisolvent systems

All-inorganic lead halide perovskites, specifically CsPbX₃ (X = I, Cl, Br), have attracted significant attention over the past few years due to their immense potential in optoelectronic devices, such as liquid crystal displays (LCDs), light emitting diodes, photodetectors, and solar cells. Currently, most available synthesis techniques rely on high temperatures, inert environments, and toxic non-polar solvents, with limiting scalability and environmental compatibility. Herein, we present a facile, room-temperature, and partially green approach for synthesizing CsPbBr₃-based particles via a biphasic solvent system comprising non-polar octadecene (ODE) layered over deionized water. By simply tuning the volume ratio of DI water to ODE, we used interfacial engineering to modulate the formation and growth of CsPbBr₃-based particles. Pure water system without ODE yielded highly crystalline, phase-pure CsPbBr₃ of ∼0.5 µm in size (BPPT0) with strong green photoluminescence at ∼534 nm. A system with 1 : 1 of water to ODE favored the formation of small CsPbBr₃ particles of ∼0.1 µm in size with trace amounts of Cs₄PbBr₆ impurity (SPPT1). The as-synthesized SPPT1 particles exhibited strong photoluminescence at ∼524 nm and broader color gamut coverage of ∼123% of NTSC 1953 and ∼174% of sRGB when being incorporated in white emitting LCD backlight structures. Further, both BPPT0 and SPPT1 displayed excellent ambient stability. This work demonstrates interfacial solvent engineering as a powerful strategy for the synthesis of size-controlled perovskite under scalable and environmentally responsible conditions.