Syntheses, Structures, Photophysical Properties and Electroluminescent Applications of Dinuclear Copper(I) Halide Complexes Containing 9-Carbazolyl-Substituted 1,2-Bis(Diphenylphosphino)Benzene

Abstract

The studies on the photophysical properties of the copper(I) halide complexes based on rigid diphosphine ligands have attracted increasing attention. Here, six copper(I) halide complexes containing 9-carbazolyl-substituted 1,2-bis(diphenylphosphino)benzene, Cu2X2(L1)2 and Cu2X2(L2)2 [L1 = 1,2-bis(9-carbazolyl)-4,5-bis(diphenylphosphino)benzene, X = I (1), Br (2), Cl (3); L2 = 1-(9-carbazolyl)-3,4-bis(diphenylphosphino)benzene, X = I (4), Br (5), Cl (6)], were synthesized and characterized. In these complexes, copper(I) centers were bridged by the halogen ligands to form dinuclear structures with four membered Cu2X2 rings. They exhibited efficient yellow green to yellowish orange delayed fluorescence in the powder states at ambient temperature, with peak wavelengths located between 548 and 602 nm (τ = 1.2–2.3 μs; Φ = 0.09–0.53). The introduction of one or two 9-carbazolyl substituents into the diphosphine resulted in the red-shifting emission, shorter decay time and higher thermal stability of complexes. The emission of the complexes originates from (metal + halide)-to-ligand and intraligand charge transitions. Organic light-emitting devices based on complex 1 exhibit yellow green luminescence with maximum external quantum efficiency of 12.0% and current efficiency of 32.64 cd A−1.

Keywords: Carbazole, Diphosphine, Cu(I) halide complex, TADF, OLED