Highly Luminescent CsPbBr₃@Cs₄PbBr₆ Nanocrystals and Their Application in Electroluminescent Emitters

Zero-dimensional perovskite nanocrystals (NCs) are becoming the most attractive material due to their excellent optical performance and better stability compared with high-dimensional perovskite. However, their application in electroluminescent (EL) emitters for high-quality displays is still limited. In this work, we successfully achieved CsPbBr₃@Cs₄PbBr₆ NCs around 13.9 ± 0.2 nm by using the hot-injection method. Additional SnBr₂ was mixed in the PbBr₂ precursor to provide extra Br^- ions and reduce the excessive amount of Pb²⁺ ions to promote the formation of CsPbBr₃@Cs₄PbBr₆. Time resolution photoluminescence analysis indicated that the green emission of our CsPbBr₃@Cs₄PbBr₆ NCs originated from the embedded CsPbBr₃ NCs, which corresponds to our previous research. The Cs₄PbBr₆ crystals passivated the surface of CsPbBr₃ NCs, resulting in the absence of trions for the high photoluminescence quantum yield. The as-synthesized CsPbBr₃@Cs₄PbBr₆ NCs were used to fabricate quantum dot light-emitting diode (QLED) devices with the highest current efficiency of 4.89 cd/A. This is the best performance of the CsPbBr₃@Cs₄PbBr₆-system QLED device, which reveals the great potential of CsPbBr₃@Cs₄PbBr₆ NCs and will inspire further study of zero-dimensional perovskite composite NCs for EL emitters.