A series of electrophosphorescent small molecular Ir3+ complexes IrPBIO22, IrPBICO, IrPBIO44 and IrPBIC22O22 for solution-processable host-free organic light-emitting diodes (OLEDs) were designed and synthesized, in which the electron-transporting 1,3,4-oxadiazole (OXD) and hole-transporting carbazole moieties were introduced through aliphatic chains to achieve balanced carrier injection/transporting. The coordinatable OXD groups were successfully and conveniently introduced through the post-substitution of Ir3+ cores. The photophysical investigation showed that compared with the single-position substituted counterparts, the double-position substitution is superior in restraining the quenching effect in solid states to endow the corresponding complexes with the much higher photoluminescence quantum yield (PLQY) in the film. The influences of peripheral carrier transporting (CT) moieties on the energy levels of frontier molecular orbitals were investigated with UPS analysis and Density Function Theory calculation. The dramatic electroluminescent (EL) performance of IrPBIC22O22 based on its host-free spin-coat phosphorescent organic light-emitting diodes (PHOLEDs), especially the remarkably restrained efficiency roll-off less than 16% at 1000 cd m−2 was realized, which demonstrated that the combined modification of the effective segregation of emitting cores by multi-position encapsulation and the balanced carrier injection/transporting through bipolar substitution is an effective strategy for realizing high-efficiency small molecular electrophosphorescent materials with the features of solution processability and strong restraining effect on quenching for host-free devices.
设计并合成了一系列电致
磷光小分子 Ir3+ 复合物 IrPBIO22、IrPBICO、IrPBIO44 和 IrPBIC22O22,这些复合物用于可溶液加工的无主有机发光二极管(OLED),其中通过脂肪族链引入了电子传输的
1,3,4-噁二唑(OXD)和空穴传输的
咔唑分子,以实现载流子的平衡注入/传输。可配位的 OXD 基团是通过后置 Ir3+ 核心而成功、方便地引入的。光物理研究表明,与单位取代的同类复合物相比,双位取代在抑制固态淬灭效应方面更具优势,从而使相应复合物在薄膜中具有更高的光致发光量子产率(PLQY)。通过
UPS 分析和密度函数理论计算,研究了外围载流子传输(CT)分子对前沿分子轨道能级的影响。基于无主自旋涂层
磷光有机发光二极管(PHOLED)的 IrPBIC22O22 实现了显著的电致发光(EL)性能,尤其是在 1000 cd m-2 时的效率衰减小于 16%、这表明,通过多位封装改变发光核的有效分离,以及通过双极置换平衡载流子注入/传输,是实现高效小分子电致
磷光材料的有效策略,同时还具有溶液可加工性和对无宿主器件淬火的强抑制作用。