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

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 CsCu2I3 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 CsCu2I3 emitter is proposed. PVK with carbazole groups is permeated at the grain boundaries of CsCu2I3 films by interacting with the uncoordinated Cu+, reducing the CuCs and CuI 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. A polymer poly(9‐vinlycarbazole) (PVK)‐modified engineering of CsCu2I3 emitter is developed to simultaneously passivate the grain boundary defects and promote the charge carrier injection for high‐performance yellow light‐emitting diodes (LEDs). As a result, the PVK‐modified device exhibits a 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.