摘要/Abstract

以手性发光材料为发光中心制备能够直接发射出圆偏振电致发光(circularly polarized electroluminescence, CPEL)的器件, 即CP-organic light-emitting diode (CP-OLED), 在3D显示领域有极大的应用前景. 本工作设计了基于八氢联萘酚的手性热激活延迟荧光材料(S/R)-OBN-tBuCz, 八氢联萘酚作为有效的手性源, 而叔丁基咔唑取代的氰基苯作为高效发光部分. 八氢联萘酚外围较多的氢原子以及较大的叔丁基可以有效增加手性发光分子的空间位阻, 降低堆积效应, 抑制浓度淬灭, 有效提升器件的发光效率. 所合成的手性发光材料展现出明亮的绿光发射(523 nm)、高的荧光量子产率(85.2%)、较小的单线态-三线态能级差ΔE_ST (0.05 eV)和优秀的热稳定性. 圆二色(CD)与圆偏振发光(CPL)光谱显示出明显的对称圆偏振发光信号, 且溶液中的g_PL为+8.6×10^-4和–6.5×10^-4. 基于(S/R)-OBN-tBuCz的电致发光器件表现出优异性能: 起亮电压为3.9 V, 最大亮度为27709 cd•m^-2, 最大电流效率为43.8 cd•A^-1, 最大功率效率为33.5 lm•W^-1, 最大外量子效率为12.4%, 效率滚降很低, 并显示出明显的圆偏振电致发光信号, g_EL分别为+1.57×10^-3和–0.90×10^-3. 大位阻手性发光材料的设计有助于实现高效的CP-OLED, 该研究能促进手性发光材料及圆偏振电致发光器件等相关研究领域的发展.
关键词: 手性发光材料, 圆偏振发光, 八氢联萘酚, 大位阻, 圆偏振有机发光二极管
Using chiral luminescent material as the emitting core in organic light-emitting diodes (OLEDs) would make these devices possess circularly polarized electroluminescence (CPEL) performance, namely CP-OLEDs, which are of great value for facilitating the development of the next generation of display technologies, especially for implementing real 3D display. In this study, a pair of octahydrobinaphthol (OBN)-based thermally activated delayed fluorescence (TADF) materials, (S/R)-OBN-tBuCz, are developed by ingeniously merging a chiral source (OBN) and a luminophore skeleton (tert-butylcarbazole cyanobenzene). The peripheral sixteen hydrogen atoms in cyclohexane part of OBN unit and the larger tertiary butyl group could effectively increase the steric hindrance of chiral luminescence molecules, reduce the intermolecular stacking effect and inhibit concentration quenching, for effectively improving the luminescence efficiency of the devices. The synthesized chiral luminescent materials exhibit bright green light emission (523 nm), high photoluminescence quantum yield (85.2%), a small ΔE_ST of 0.05 eV with TADF property as well as excellent thermal stability. The chiroptical properties of (S/R)-OBN-tBuCz enantiomers in the ground and excited states are investigated by circular dichroism (CD) and circularly polarized luminescence (CPL) spectra, and the strong symmetrically circularly polarized luminescent signals with g_PL of +8.6×10^-4 and –6.5×10^-4 in toluene solution are observed for (S)-OBN-tBuCz and (R)-OBN-tBuCz, respectively, indicating that the chirality is successfully induced into the TADF skeleton through chirality transmitting of OBN unit. Considering the efficient TADF and CPL properties, the enantiomers are employed as chiral emitters for fabricating CP-OLEDs. The electroluminescent devices based on (S/R)-OBN-tBuCz exhibit decent performances with the turn-on voltage of 3.9 V, the maximum brightness of 27709 cd•m^-2, the maximum current efficiency of 43.8 cd•A^-1, the maximum power efficiency of 33.5 lm•W^-1, the maximum external quantum efficiency of 12.4% and low efficiency roll-off as well as obvious circularly polarized electroluminescence signals with g_EL of +1.57×10^-3 and –0.90×10^-3, respectively. The design strategy of rationally merging chiral source and TADF skeleton can promote the development of chiral luminescent materials and circularly polarized electroluminescent devices.
Key words: chiral luminescent material, circularly polarized luminescence, octahydrobinaphthol, large steric hindrance, circularly polarized organic light-emitting diodes


PDF全文下载地址:

点我下载PDF