Optimizing luminescence performance of alloyed CsPb1−xCdxBr3 perovskite nanocrystals for blue light-emitting diodes

It is crucial to obtain pure blue perovskite nanocrystals (NCs) with high photoluminescence quantum yield (PL QY) and good stability. This work focuses on optimizing the luminescence properties of CsPbBr₃ NCs through the introduction of Cd²⁺, aiming to achieve stable and efficient pure blue perovskite NCs. By employing an improved hot-injection method, we successfully synthesized alloyed CsPb_1-xCd_xBr₃ NCs. The introduction of Cd²⁺ not only significantly tunes the bandgap of the NCs, realizing a blueshift in the emission wavelength, but also enhances the PL QY and stability of the NCs. Notably, the highest PL QY of 98% is achieved at a Cd/Pb molar ratio of 1:1. The changes in the luminescence properties of the NCs are attributed to lattice distortion induced by the incorporation of Cd²⁺, leading to a gradual transition from the CsPbBr₃ phase to the Cs(Pb/Cd)Br₃ and CsCdBr₃ phases. The alloyed CsPb_1-xCd_xBr₃ NCs exhibit a smaller temperature dependent bandgap variation rate and a larger exciton binding energy, improving the water and thermal stability. Finally, we fabricated blue light emitting diodes (LEDs) using the alloyed CsPb_1-xCd_xBr₃ NCs, achieving a maximum external quantum efficiency of 1.95% and a maximum brightness of 489.44 cd/m². This study provides a material foundation for developing high-performance blue LED devices.