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.