Three new bipolar molecules composed of carbazole, triarylamine, and bipyridine were synthesized and utilized as host materials in multi-color phosphorescent OLEDs (PhOLEDs). These carbazole-based materials comprise a hole-transport triarylamine at C3 and an electron-transport 2,4′- or 4,4′-bipyridine at N9. The different bipyridine isomers and linking topology of the bipyridine with respect to carbazole N9 not only allows fine-tuning of physical properties but also imparts conformational change which subsequently affects molecular packing and carrier transport properties in the solid state. PhOLEDs were fabricated using green [(ppy)₂Ir(acac)], yellow [(bt)₂Ir(acac)], and red [(mpq)₂Ir(acac)] as doped emitters, which showed low driving voltage, high external quantum efficiency (EQE), and extremely low efficiency roll-off. Among these new bipolar materials, the 2Cz-44Bpy-hosted device doping with 10% (ppy)₂Ir(acac) as green emitting layer showed a high EQE of 22% (79.8 cd A⁻¹) and power efficiency (PE) of 102.5 lm W⁻¹ at a practical brightness of 100 cd m⁻². In addition, the device showed limited efficiency roll-off (21.6% EQE) and low driving voltage (2.8 V) at a practical brightness of 1000 cd m⁻².

合成了由咔唑，三芳基胺和联吡啶组成的三个新的双极性分子，并将其用作多色磷光OLED（PhOLED）的主体材料。这些基于咔唑的材料在C3处包含空穴传输的三芳基胺，在N9处包含电子传输的2,4'-或4,4'-联吡啶。相对于咔唑N9，不同的联吡啶异构体和联吡啶的连接拓扑结构不仅可以对物理性质进行微调，还可以提供构象变化，从而影响固态下的分子堆积和载流子传输特性。使用绿色[（ppy）₂ Ir（acac）]，黄色[（bt）₂ Ir（acac）]和红色[（mpq）₂Ir（acac）]作为掺杂发射极，其显示出低驱动电压，高外部量子效率（EQE）和极低的效率滚降。在这些新的双极材料中，掺有10％（ppy）₂ Ir（acac）作为绿色发射层的2Cz-44Bpy承载的器件显示出22％（79.8 cd A ^-1）的高EQE和功率效率（PE）为 在100 cd m ^-2的实际亮度下为102.5 lm W ^-1。此外，该器件在实用亮度1000 cd m ^-2时显示出有限的效率下降（21.6％EQE）和低驱动电压（2.8 V）。