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

Perovskite CsPbBr 3 /Rb 4 PbBr 6 yolk–shell structure was synthesized by using the hot injection method. X-ray diffraction confirms that the crystal structure of CsPbBr 3 NCs remains unaffected after being encapsulated with Rb 4 PbBr 6 coating. The photoluminescence (PL) intensity of the CsPbBr 3 /Rb 4 PbBr 6 yolk–shell structure is 1.5 times greater than that of CsPbBr 3 NCs. The PL lifetime of the CsPbBr 3 /Rb 4 PbBr 6 yolk–shell structure increases by 2 orders of magnitude compared to that of CsPbBr 3 NCs. This indicates that the surface defects of CsPbBr 3 NCs have been successfully passivated by Rb 4 PbBr 6 coating, thereby suppressing nonradiative recombination. Importantly, the water stability and thermal stability of the CsPbBr 3 /Rb 4 PbBr 6 yolk–shell structure have been significantly enhanced. Subsequently, the CsPbBr 3 /Rb 4 PbBr 6 yolk–shell structure was dispersed in methyl methacrylate to prepare CsPbBr 3 /Rb 4 PbBr 6 /PMMA organic glasses (OGs). The air stability of the CsPbBr 3 /Rb 4 PbBr 6 /PMMA OGs has been improved. The temperature-dependent PL spectra of CsPbBr 3 NCs and the CsPbBr 3 /Rb 4 PbBr 6 yolk–shell structure were studied. The high PL intensity and long lifetime of the CsPbBr 3 /Rb 4 PbBr 6 yolk–shell structure are attributed to the enhanced electron–hole interactions. Additionally, green light-emitting diodes fabricated with the CsPbBr 3 /Rb 4 PbBr 6 yolk–shell structure and CsPbBr 3 /Rb 4 PbBr 6 /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.