A novel dual optimization reagent enables ultra-bright and air-stable cesium copper iodine thin films

Cesium copper iodine (CsCuI) perovskite LED (PeLED) possesses several advantages, including eco-friendly, high stability, abundant elements, and low cost. Improving the photoluminescent performance and stability of the CsCuI perovskite thin film, which serves as the emissive layer, is crucial for enhancing the overall PeLED performance. This paper reports a dual optimization strategy (DOS) that uses a novel mixed toluene (Tol) and oleic acid (OA) reagent. Tol acts as an antisolvent, and OA serves as a passivator. Experimental results show that the DOS increases crystal nucleation rate and mitigates film defects. The photoluminescence quantum yield (PLQY) of the Cs 3 Cu 2 I 5 perovskite thin film prepared by DOS exceeds 90 %, and after 40 days of storing in air, the PLQY remains at the initial 88 %. This DOS, mixing antisolvent and passivator, also provides new ideas for improving other lead-free metal halide perovskites.