Mononuclear Cu(I) halide complexes with two thiophenyl rings triphosphine: Structure and photophysical properties

Rigid aryl ring-based triphosphine can be used to construct highly emissive Cu(I) halide complexes applied in OLEDs, but rigid heteroaryl ring-based triphosphine Cu(I) halide complexes are rarely reported. Here, six mononuclear copper(I) halide complexes with two thiophenyl rings triphosphine CuX (L1) and CuX (L2) [L1 = (2,5-Me-3-PPh₂-C₄S)₂PPh, X = I (1), Br (2) Cl (3); L2 = (3-PPh₂-C₄H₂S)₂PPh, X = I (4), Br (5) Cl (6)], were successfully synthesized and characterized on their structures and photophysical properties. The introduction of four methyl groups into two thiophenyl rings, improves the solubility and quantum yield, and fine-tunes the light-emitting color of complexes. At room temperature, complexes 1–6 in powder state exhibit intense green to yellow green delayed fluorescence (λ_em = 502–528 nm, τ = 16.1–63.0 μs, Φ = 0.21–0.35 for 1–3; λ_em = 507–559 nm, τ = 3.9–13.3 μs; Φ = 0.04–0.27 for 4–6). The emissions of the complexes 1–6 are originated from (metal + halide) to ligand and intra-ligand charge transitions. Solution-processed, complex 3-based nondoped and doped devices emit yellow and yellow green light with CIE of (0.48, 0.48) and (0.41, 0.51), respectively. The doped device achieves a maximum external quantum efficiency (EQE) of 3.12%, and a maximum luminance of 2280 cd/m². The EQE value is the highest among reported mononuclear Cu(I) halide complexes with triphosphine based devices by solution-processed method.