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

Abstract

AbstractThe 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 (Cu2S) lattice‐connectedly capping over Cs3Cu2I5 to form lattice‐matched core/shell nanocrystals (NCs) by controlling the reactivity of sulfur (S) precursor in the synthesis. Interestingly, the resultant Cs3Cu2I5/Cu2S NCs significantly enhance the hole mobility compared to Cs3Cu2I5 NCs. Besides, the photoluminescence quantum yield of Cs3Cu2I5 NCs increases from 26.8% to 70.6% after the Cu2S lattice‐connected capping. Consequently, by establishing the structure of CsCu2I3/Cs3Cu2I5/Cu2S 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.