Enhancing stability of red perovskite nanocrystals through copper substitution for efficient light-emitting diodes

Red perovskite nanocrystals (NCs) are important for efficient perovskite light-emitting diodes (PeLEDs). However, the implementation of these red perovskite NCs are hindered because of their low structural stability. In the present work, highly stable and luminescent red perovskite CsPbBrI2 NCs were achieved through copper substitution and halide rich passivation strategy. Because the ion radius of Cu2+ (0.72 Å) is smaller than that of Pb2+ (1.19 Å), divalent Cu2+ cations can partly replace the Pb2+ ions in the lattice structure of CsPbBrI2 NCs. We demonstrated that the incorporation of Cu2+ ions can enhance formation energy, cause a slight lattice contraction, and hence stabilize the cubic phase of these NCs. On the other hand, Cu2+-substituted CsPbBrI2 NCs with higher luminescence were synthesized in a halide-rich passivation method. Benefiting from such an effective substitution and halide-rich strategy, these Cu2+-substituted CsPbBrI2 NCs has shown excellent performance with photoluminescence quantum yield (PL QY) (up to 94.8%) and an improved stability. The highly stable and luminescent Cu2+-substituted CsPbBrI2 NCs can function well as efficient light emitters toward the fabrication of high-performance red perovskite LEDs.