Potassium Iodide Passivation Enabling Performance Improvement of CsCu₂I₃-Based LEDs

Abstract

Ternary copper halide CsCu $_{\mathbf {{2}}}$ I $_{\mathbf {{3}}}$ emerges as a highly promising candidate for eco-friendly light-emitting diodes (LEDs), but the electroluminescent performance is limited by defect-related nonradiative losses and disordered crystallization. Herein, we develop a potassium iodide (KI)-modified engineering of CsCu $_{\mathbf {{2}}}$ I $_{\mathbf {{3}}}$ emitters to passivate the defects by compensating for any halide vacancies, and reduce trap state density. Meanwhile, this strategy can optimize the crystallization process of CsCu $_{\mathbf {{2}}}$ I $_{\mathbf {{3}}}$ to obtain continuous high-quality CsCu $_{\mathbf {{2}}}$ I $_{\mathbf {{3}}}$ films, which is conductive to suppressing leakage current of corresponding devices. Benefitting from the suppression of nonradiative recombination due to the reduced halide vacancies, and improved film morphology of CsCu $_{\mathbf {{2}}}$ I $_{\mathbf {{3}}}$ by optimizing the crystallization process of CsCu $_{\mathbf {{2}}}$ I $_{\mathbf {{3}}}$ , the EQE of corresponding LED is largely improved from 0.02% to 0.065%. The results highlight the great potential of KI passivation for high performance eco-friendly CsCu $_{\mathbf {{2}}}$ I $_{\mathbf {{3}}}$ based LED.