HCOO--induced defects passivation of Cs3Cu2I5 for enhanced blue emission and application in white light emission

Abstract

Cs3Cu2I5 nanocrystals (NCs) have emerged as promising environmentally friendly alternatives for blue perovskite materials, owing to copper’s advantageous combination of low cost, earth abundance, and non-toxicity. However, due to their 0D crystal dimension, Cs3Cu2I5 NCs exhibits a large surface area, which promotes iodine vacancy formation and consequently lowers carrier recombination efficiency, impairing light emission. Herein, we incorporated an excess of HCOOCs to promote radiative recombination through carboxyl ligand coordination. FTIR and XPS analyses revealed a strong interaction between carboxyl groups and Cu+, demonstrating their role in passivating vacancy defects and suppressing non-radiative recombination pathways. Benefiting from efficient defect passivation, the HCOO--engineered Cs3Cu2I5 exhibited a remarkable PLQY of 87.5%, substantially higher than the 30.2% observed for pristine Cs3Cu2I5. Furthermore, the optimized HCOO--Cs3Cu2I5 displayed outstanding emission stability, retaining more than 88% of its initial PL intensity after 100 days of storage under ambient conditions. We further fabricated a WLED device incorporating the HCOO--engineered Cs3Cu2I5, achieving CIE coordinates of (0.32, 0.33) and a CEI of 83.7. The proposed HCOO--ligand modification strategy offers a promising approach to simultaneously enhance both luminescent performance and stability of Cs3Cu2I5 for practical applications.