A long lifetime is one of requirements for the commercialization of organic light-emitting diodes (OLEDs). In this paper, we improved the device lifetime of phosphorescent OLEDs by enhancing the oxidation stability of the hole-transport-type host because the host material with steadiness against oxidation has a good positive polaron stability for improved device lifetime. Two p-type host materials, 9-(dibenzo[b,d]thiophen-2-yl)-3′,6,6′-triphenyl-9H-3,9′-bicarbazole (2-TPhDCz) and 9-(dibenzo[b,d]thiophen-4-yl)-3′,6,6′-triphenyl-9H-3,9′-bicarbazole (4-TPhDCz), were synthesized for improved positive polaron stability to obtain a long device lifetime in phosphorescent OLEDs by substituting the active site of a carbazole unit with a phenyl unit. The oxidation stability and positive polaron stability of the host were enhanced by the phenyl protection of the active site, which extended the device lifetime of the phosphorescent OLEDs compared with conventional hole-transport-type hosts. In particular, the 2-TPhDCz host doubled the device lifetime of the phosphorescent OLEDs.

中文翻译：

---

提高 p 型主体的正极极化子稳定性，延长磷光有机发光二极管的使用寿命

长寿命是有机发光二极管 (OLED) 商业化的要求之一。在本文中，我们通过提高空穴传输型主体的氧化稳定性来提高磷光 OLED 的器件寿命，因为具有抗氧化稳定性的主体材料具有良好的正极性稳定性，从而提高了器件寿命。两种 p 型主体材料，9-(dibenzo[ b , d ]thiophen-2-yl)-3', 6,6'- triphenyl-9 H -3,9'-bicarbazole ( 2-TPhDCz ) 和 9- (dibenzo[ b , d ] thiophen-4-yl)-3', 6,6'- triphenyl-9 H -3,9'-bicarbazole ( 4-TPhDCz)，通过用苯基单元取代咔唑单元的活性位点，合成了提高正极极化子稳定性，从而在磷光 OLED 中获得较长的器件寿命。活性位点的苯基保护增强了主体的氧化稳定性和正极极化子稳定性，与传统的空穴传输型主体相比，这延长了磷光 OLED 的器件寿命。特别是，2-TPhDCz主体使磷光 OLED 的器件寿命延长了一倍。