Synthesis of CsPbBr₃ and Transformation into Cs₄PbBr₆ Crystals for White Light Emission with High CRI and Tunable CCT

Saponification approach was employed to synthesize all-inorganic halide perovskites at an ambient atmosphere. We report the conversion from CsPbBr 3 to lead-depleted Cs 4 PbBr 6 crystals by varying the amount of Cs-oleate precursor at room-temperature synthesis. This transformation drastically changes the morphology as well as the structure and hence the optical properties of the perovskites. The cubic CsPbBr 3 nanoplatelets with a strong blue emission (462 nm) attenuate a green (529 nm) emission when the material crystallizes in the rhombohedral phase (Cs 4 PbBr 6 ), which demonstrates the intrinsic luminescence nature of the Cs 4 PbBr 6 crystals. In addition, we proposed to combine these two compounds with the yellow- and red-emitting perovskites to generate white light emission. The correlated color temperature is tuned from 2480 to 9134 K and the color rendering index (CRI) is maximized up to 96, the highest CRI yet known for these types of materials. These characteristics demonstrate the high potential to replace conventional phosphors in lighting devices.