A Copper(I)‐Carbene Complex With High Quantum Yield for White Light Emitting Application

ABSTRACT A novel tri‐coordinated dinuclear copper(I) N ‐heterocyclic carbene complex, [Cu 2 (L 1 ) 2 ]I 2 ( 1 ), (where L 1 = 1,3‐bis((1‐mesityl‐1,2,3‐triazol‐4‐yl)methyl)‐benzimidazole) with excellent photoluminescence properties was isolated from the reaction between CuI and L 1 .HBr. The copper(I) complex was characterized by FT‐IR, TGA, DTA, and single‐crystal X‐ray diffraction techniques. The three‐coordinated copper center in 1 exhibited a distorted trigonal planar geometry. 1 is thermally stable till 258°C. 1 emits a greenish‐blue color at 497 nm due to halide‐metal to ligand charge transfer with Commission Internationale de l'Eclairage (CIE) values of x = 0.19 and y = 0.43. It possesses a remarkably high quantum yield of 84% with a lifetime of 9.6 µs at room temperature. DFT studies reveal that HOMO is mainly located on the copper‐iodide center, and the LUMO is dispersed on the NHC ligand, supporting charge transfer mechanism. The greenish‐blue emitter 1 was combined with a red‐emitting Eu(III) complex to fabricate a white LED exhibiting CIE (0.37, 0.32), color rendering index of 70 and a low correlated color temperature of 3182 K. The fabricated LED achieves luminous efficiency of radiation (LER) of around 365 lm W −1 , highlighting 1 as promising candidate for potential applications in optoelectronics and lighting.