Carbazole‐Containing Polymer‐Assisted Trap Passivation and Hole‐Injection Promotion for Efficient and Stable CsCu₂I₃‐Based Yellow LEDs

Abstract

Perovskite light-emitting diodes (LEDs) are emerging light sources for next-generation lighting and display technologies; however, their development is greatly plagued by difficulty in achieving yellow electroluminescence, environmental instability, and lead toxicity. Copper halide CsCu₂ I₃ with intrinsic yellow emission emerges as a highly promising candidate for eco-friendly LEDs, but the electroluminescent performance is limited by defect-related nonradiative losses and inefficient charge transport/injection. To solve these issues, a hole-transporting poly(9-vinlycarbazole) (PVK)-incorporated engineering into CsCu₂ I₃ emitter is proposed. PVK with carbazole groups is permeated at the grain boundaries of CsCu₂ I₃ films by interacting with the uncoordinated Cu⁺ , reducing the Cu_Cs and Cu_I antisite defects to increase the radiative recombination and enhancing the hole mobility to balance the charge transport/injection, resulting in substantially enhanced device performances. Eventually, the yellow LEDs exhibit an 8.5-fold enhancement of external quantum efficiency, and the half-lifetime reaches 14.6 h, representing the most stable yellow LEDs based on perovskite systems reported so far.