Bluish-Green Cu(I) Dimers Chelated with Thiophene Ring-Introduced Diphosphine Ligands for Both Singlet and Triplet Harvesting in OLEDs

Two new Cu­(I) dimers chelated with thiophene ring-introduced diphosphine ligands [Cu­(μ2-I)­dppt1]2 and [Cu­(μ2-I)­dppt2]2 (dppt1 = 3,4-bis­(diphenylphosphino)­thiophene, dppt2 = 2,3-bis­(diphenylphosphino)­thiophene) have been prepared and studied in terms of photoluminescence and electroluminescence properties. Both dimers exhibited two independent radiative decay pathways, which are equilibrated thermally at room temperature: one is thermally activated delay fluorescence (TADF) via the first singlet excited state (S1) decay and the other is phosphorescence via the first triplet excited state (T1) decay. The dual emission mechanism for both singlet and triplet harvesting, as well as excellent photoluminescence properties such as bluish-green emission color (487 and 483 nm), short decay times (9.46 and 7.62 μs), and high photoluminescence quantum yields (69% and 86%) of the two Cu­(I) dimers, implies their potential to be highly efficient emitter molecules for organic light emitting diode (OLED) applications. As a result, the optimized OLEDs with [Cu­(μ2-I)­dppt2]2 showed the highest efficiency, exhibiting a current efficiency up to 32.2 cd A–1, a peak brightness of 3.67 × 103 cd m–2, as well as a maximum external quantum efficiency of 14.5%.两种以引入噻吩环的双膦配体螯合的新型铜(I)二聚体[Cu(μ₂-I)dppt1]₂与[Cu(μ₂-I)dppt2]₂（其中dppt1=3,4-双(二苯基膦基)噻吩，dppt2=2,3-双(二苯基膦基)噻吩）已被合成，并针对其光致发光（photoluminescence）与电致发光（electroluminescence）性能开展了系统研究。两种二聚体均存在两条独立的辐射衰变路径，二者在室温下处于热平衡状态：其一为经由第一单重激发态（S₁）衰变的热激活延迟荧光（TADF），其二为经由第一三重激发态（T₁）衰变的磷光。这两种铜(I)二聚体兼具单重态与三重态捕获的双发射机制，同时具备优异的光致发光性能：包括487 nm与483 nm的蓝绿色发射波长、9.46 μs与7.62 μs的较短衰变寿命，以及69%与86%的高光致发光量子产率，这表明它们具备作为高效发光分子应用于有机发光二极管（OLED）的潜力。最终，采用[Cu(μ₂-I)dppt2]₂制备的优化型OLED器件展现出最优综合性能：电流效率最高可达32.2 cd·A⁻¹，峰值亮度达3.67×10³ cd·m⁻²，最大外量子效率为14.5%。