Highly Luminescent CsPbBr₃@Cs₄PbBr₆ Nanocrystals and Their Application in Electroluminescent\nEmitters

Abstract

Zero-dimensional\nperovskite nanocrystals (NCs) are becoming the\nmost attractive material due to their excellent optical performance\nand better stability compared with high-dimensional perovskite. However,\ntheir application in electroluminescent (EL) emitters for high-quality\ndisplays is still limited. In this work, we successfully achieved\nCsPbBr₃@Cs₄PbBr₆ NCs around 13.9\n± 0.2 nm by using the hot-injection method. Additional SnBr₂ was mixed in the PbBr₂ precursor to provide extra\nBr^– ions and reduce the excessive amount of Pb²⁺ ions to promote the formation of CsPbBr₃@Cs₄PbBr₆. Time resolution photoluminescence analysis\nindicated 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\nquantum yield. The as-synthesized CsPbBr₃@Cs₄PbBr₆ NCs were used to fabricate quantum dot light-emitting\ndiode (QLED) devices with the highest current efficiency of 4.89 cd/A.\nThis is the best performance of the CsPbBr₃@Cs₄PbBr₆-system QLED device, which reveals the great potential\nof CsPbBr₃@Cs₄PbBr₆ NCs and will\ninspire further study of zero-dimensional perovskite composite NCs\nfor EL emitters.