Evolution and Mechanism of Cesium Lead Bromide Nanostructures in Oleylamine‐Rich System by Hot‐Injection Method

Abstract Due to the ultrafast nucleation and growth rates of perovskite nanostructures during the synthesis, the products are difficult to control, such as its derivatives (e.g., Cs 4 PbBr 6 ) often appear. Here, the hot‐injection method is ameliorated by using oleylamine (OAm) instead of octadecene as solvent. The results reveal that in OAm‐rich system, the pure nanostructures with different Pb/Br ratios (CsBr, Cs 4 PbBr 6 , and CsPbBr 3 ) can be obtained at different reaction temperatures, and thus controlling the Pb‐Br linkage and the interconnection of [PbBr 6 ] 4− octahedra, and resulting in the formation of different nanostructures. As the reaction temperature increases from 120 to 180 °C, the products change from lead‐free CsBr nanocrystals to poor‐lead Cs 4 PbBr 6 nanocrystals and finally to normal CsPbBr 3 nanocubes and nanowires. Moreover, the synthesized CsPbBr 3 nanowires exhibit an emission peak at 521 nm, full width at half maximum (FWHM) of 19 nm, with photoluminescence quantum yields (PLQY) of 64.9%, and high stability. Furthermore, the white light‐emitting diode (WLED) devices are successfully fabricated based on the obtained CsPbBr 3 nanowires, showing high‐intensity white light and high stability without any encapsulation. Remarkably, this work provides a new approach for elucidating the synthesis mechanism of perovskite nanomaterials and their applications.