Efficient Large‐Area (81 cm2) Ternary Copper Halides Light‐Emitting Diodes with External Quantum Efficiency Exceeding 13% via Host‐Guest Strategy

Ternary copper (Cu) halides are promising candidates for replacing toxic lead halides in the field of perovskite light-emitting diodes (LEDs) toward practical applications. However, the electroluminescent performance of Cu halide-based LEDs remains a great challenge due to the presence of serious nonradiative recombination and inefficient charge transport in Cu halide emitters. Here, the rational design of host-guest [dppb]