Synchronous Defect Passivation and Interfacial Dipole Engineering for Efficient and Stable Cesium Copper Iodine Yellow LEDs

ABSTRACT Recently, substantial progresses have been made in developing perovskite‐based light‐emitting diodes (LEDs) for next‐generation lighting and display technologies. While, their development is greatly plagued by difficulty in achieving yellow electroluminescence. Ternary copper halide CsCu 2 I 3 with intrinsic yellow emission has emerged as a highly promising alternative to lead‐halide perovskites for yellow LEDs. However, the device performances remain severely limited by defect‐related nonradiative losses and inefficient carrier injection and recombination processes. Here, we propose a synchronous strategy combining defect passivation and interfacial dipole engineering to enhance the device performance. Organic molecule triethanolamine with multiple coordination groups was first used to passivate the uncoordinated defects and assist the crystallization of perovskites to form compact and smooth films. Further, a thin MoO 3 dipole layer was introduced between the hole transport layer and emissive layer to promote hole injection and enhance the recombination rate of injected carriers. Eventually, the best‐performing device achieves an external quantum efficiency of 1.67%, showing a 6.4‐fold enhancement compared with the pristine device (0.26%). Moreover, the proposed LEDs, even without encapsulation, demonstrate a substantially improved operation stability against water and oxygen degradation. Thus, this work provides effective guidelines for the development of efficient and eco‐friendly metal halide yellow LEDs.