Stabilized Yolk–Shell Perovskite CsPbBr₃/Rb₄PbBr₆ Nanocrystals for Green-Emitting Light-Emitting Diodes

Perovskite CsPbBr3/Rb4PbBr6 yolk–shell structure was synthesized by using the hot injection method. X-ray diffraction confirms that the crystal structure of CsPbBr3 NCs remains unaffected after being encapsulated with Rb4PbBr6 coating. The photoluminescence (PL) intensity of the CsPbBr3/Rb4PbBr6 yolk–shell structure is 1.5 times greater than that of CsPbBr3 NCs. The PL lifetime of the CsPbBr3/Rb4PbBr6 yolk–shell structure increases by 2 orders of magnitude compared to that of CsPbBr3 NCs. This indicates that the surface defects of CsPbBr3 NCs have been successfully passivated by Rb4PbBr6 coating, thereby suppressing nonradiative recombination. Importantly, the water stability and thermal stability of the CsPbBr3/Rb4PbBr6 yolk–shell structure have been significantly enhanced. Subsequently, the CsPbBr3/Rb4PbBr6 yolk–shell structure was dispersed in methyl methacrylate to prepare CsPbBr3/Rb4PbBr6/PMMA organic glasses (OGs). The air stability of the CsPbBr3/Rb4PbBr6/PMMA OGs has been improved. The temperature-dependent PL spectra of CsPbBr3 NCs and the CsPbBr3/Rb4PbBr6 yolk–shell structure were studied. The high PL intensity and long lifetime of the CsPbBr3/Rb4PbBr6 yolk–shell structure are attributed to the enhanced electron–hole interactions. Additionally, green light-emitting diodes fabricated with the CsPbBr3/Rb4PbBr6 yolk–shell structure and CsPbBr3/Rb4PbBr6/PMMA OGs have stable light conversion and maintain high color output quality. This research offers an effective method for the fabrication of perovskite-based optoelectronic devices.