基于双极性铼配合物的低浓度淬灭电致发光器件

合成了一种含双极性9,9-双(9-乙基咔唑-3-基)-4,5-二氮芴(ECAF)配体的新型三羰基铼配合物Re(CO)3(ECAF)Cl,通过核磁共振氢谱及高分辨质谱对其结构进行了确定。以含有4,5-二氮-9,9-螺二芴(SB)配体的铼配合物Re(CO)3(SB)Cl作为参比物,对比研究了其热稳定性及光电性能。结果表明,与参比物的分解温度(366℃)相比,配合物Re(CO)3(ECAF)Cl有极好的热稳定性(热分解温度419℃)。由于富电子咔唑基团导致的能隙增大,相比参比物的发光波长(572 nm),Re(CO)3(ECAF)Cl的发光波长蓝移至565 nm。Re(CO)3(ECAF)Cl的发光量子效率(39%)稍高于参比物(37%)。以旋涂法制成电致发光器件后,基于Re(CO)3(ECAF)Cl器件的最佳掺杂浓度(质量分数)高达30%,是基于参比物器件的2.4倍,而且开启电压低至2.9 V,明显比参比物器件的4.0 V低,说明ECAF配体能有效抑制发光浓度淬灭,且明显改善了铼配合物的载流子传输性能。基于Re(CO)3(ECAF)Cl器件的最大电流效率及最大外量子效率分别为8.2 cd·A^-1和3.0%,低于参比物器件的9.7 cd·A^-1和3.9%。

Low Concentration Quenched Electroluminescent Devices Based on Bipolar Rhenium Complexes

A novel tricarbonyl complex Re(CO)3(ECAF)Cl containing the bipolar(9,9-bis(9-ethylcarbazol-3-yl)-4,5-diazafluorene(ECAF) ligand was synthesized and characterized by NMR spectroscopy and high resolution mass spectrometry. In order to study the thermal stability and photoelectric properties of complex Re(CO)3(ECAF)Cl,the reference complex Re(CO)3(SB)Cl containing 4,5-diazo-9,9-spirodifluorene(SB) ligand was also synthesized.Compared with the decomposition temperature of reference(366 ℃), complex Re(CO)3(ECAF)Cl(419 ℃) exhibited better thermal stability. As a result of the increase of the optical energy gap caused by the electron-rich carbazole group, compared with the luminescence wavelength of reference complex(572 nm), the wavelength of Re(CO)3(ECAF)Cl blue-shifted to 565 nm. The luminescent quantum efficiency(39%) of Re(CO)3(ECAF)Cl was slightly higher than that of the reference material(37%). The spin-coating electroluminescent devices were fabricated, and the optimized doping concentration of Re(CO)3(ECAF)Cl-based device was as high as 30%, which was 2.4 times that of the reference complex-based device. The quite low turn-on voltage(2.9 V) of Re(CO)3(ECAF)Cl-based device was significantly less than that of reference complex-based device(4.0 V), reflecting that ECAF can depress luminescent quenching and improve the charge transporting performance of complexes significantly. The maximum current efficiency and maximum external quantum efficiency of Re(CO)3(ECAF)Cl-based devices were 8.2 cd·A-1 and 3.0%, respectively, which were lower than the efficiencies(9.7 cd·A-1 and 3.9%) of reference complex-based device. These results show that bipolar ECAF ligand is an excellent ligand for luminescent rhenium complexes.