Efficient White Electroluminescence from Cu‐based Perovskite Achieved by High Hole Injection Core/Shell Structures

Abstract The copper‐based (Cu‐based) halide perovskite possesses eco‐friendly features, bright self‐trapped‐exciton (broadband) emission, and a high color‐rendering index (CRI) for achieving white emission. However, the limited hole injection (HI) of Cu‐based perovskites has been bottle‐necking the efficiency of white electroluminescence and thus their application in white perovskite light‐emitting diodes (W‐PeLEDs). In this study, we demonstrate a p‐type cuprous sulfide (Cu 2 S) lattice‐connectedly capping over Cs 3 Cu 2 I 5 to form lattice‐matched core/shell nanocrystals (NCs) by controlling the reactivity of sulfur (S) precursor in the synthesis. Interestingly, the resultant Cs 3 Cu 2 I 5 /Cu 2 S NCs significantly enhance the hole mobility compared to Cs 3 Cu 2 I 5 NCs. Besides, the photoluminescence quantum yield of Cs 3 Cu 2 I 5 NCs increases from 26.8% to 70.6% after the Cu 2 S lattice‐connected capping. Consequently, by establishing the structure of CsCu 2 I 3 /Cs 3 Cu 2 I 5 /Cu 2 S in W‐PeLEDs, an external quantum efficiency of 3.45% and a CRI of 91 is realized, representing the highest reported electroluminescent performance in lead‐free Cu‐based W‐PeLEDs. These findings contribute to establishing guidelines and effective strategies for designing broadband electroluminescent materials and device structures of PeLEDs.