Syntheses, Crystal Structures and Photophysical Properties of Dinuclear Copper(I) Complexes Bearing Diphenylphosphino‐Substituted Benzimidazole Ligands

Three dinuclear copper(I) complexes (1, 2 and 3) of the form [(P N)Cu]2(μ2‐I)2 have been designed and synthesized with 4‐diphenylphosphino‐benzimidazole (P N) derivatives. X‐ray structural analysis shows that the complexes possess one rhombohedral Cu2I2 dimer that is coordinated with two P N ligands and exhibits a trans‐configuration. At 290 K, the copper complexes exhibit similar broad and featureless emission bands with peak maxima (λmax) at 585 nm, 565 nm and 586 nm, respectively. The temperature‐dependent photophysical behaviors accompanied with the theory calculations demonstrate that 1 represents a thermally activated delayed fluorescence behavior at ambient temperature, whereas luminescence of 2 and 3 is phosphorescence. Moreover, the complexes (1–3) achieve high photoluminescence quantum yields of 36.9 %, 43.0 % and 34.0 % with relatively short emission decay times of 5.85 μs, 7.99 μs and 5.99 μs, respectively. The solution‐processed organic light‐emitting diode based on 1 achieves a peak brightness of 3325 cd m−2 and an EQE of 2.99 %. Due to the structural rigidity as well as synergistic heavy atom (Cu and I) effects, the complexes (1–3) achieve high luminescence properties. Additionally, the Cu(I) complexes realize different radiative mechanism as a result of the substituent effect: 1 exhibits thermally activated delayed fluorescence (TADF), 2 and 3 exhibit phosphorescence. The solution‐processed organic light‐emitting diode based on TADF‐type emitter 1 exhibits a reduced efficiency roll‐off and achieves a peak brightness of 3325 cd m−2.