Carbazole-based polysiloxane hosts for highly efficient solution-processed blue electrophosphorescent devices
作者:Dianming Sun、Qiang Fu、Zhongjie Ren、Wei Li、Huihui Li、Dongge Ma、Shouke Yan
DOI:10.1039/c3tc31108b
日期:——
The efficient host materials containing carbazole moieties linked to the backbone of polysiloxane through a phenyl bridge have been synthesized and characterized. They exhibit good film forming ability, high thermal decomposition temperatures and suitable glass transition temperatures, so as to form stable amorphous states. Moreover, the silicon–oxygen linkage disrupts their conjugation and results in a sufficiently high triplet energy level (3.0 eV). Iridium bis(4,6-difluorophenyl)pyridinato-N,C2 picolinate (FIrpic)-based devices using them as hosts show good overall performance with low efficiency roll-off. The device using PCzMSi as the host demonstrates the best performance with a maximum current efficiency of 22.8 cd A−1, a maximum power efficiency of 9.4 lm W−1 and a maximum external quantum efficiency of 11.9% at a practical luminance of 1165 cd m−2. Even at a brightness of 5000 cd m−2 level, the external quantum efficiency (EQE) still remains as high as 10%, suggesting a gentle roll-off of device efficiency at high current density. In addition, typically, the host PCzMSi film displays good mechanical performance by a nanoindentation technique to meet the practical application. These results demonstrate that the design of polysiloxane-based host materials is a promising approach to realize high performance solution-processed blue phosphorescent polymer light emitting diodes (PhPLEDs).
我们合成了含有咔唑分子并通过苯基桥与聚硅氧烷骨架相连的高效主材料,并对其进行了表征。它们具有良好的成膜能力、较高的热分解温度和合适的玻璃化转变温度,从而形成稳定的非晶态。此外,硅氧连接破坏了它们的共轭作用,并产生了足够高的三重能级(3.0 eV)。以双(4,6-二氟苯基)吡啶-N,C2吡啶甲酸铱(FIrpic)为宿主的器件显示出良好的整体性能和较低的效率衰减。使用 PCzMSi 作为宿主的器件性能最佳,在实际亮度为 1165 cd m-2 时,最大电流效率为 22.8 cd A-1,最大功率效率为 9.4 lm W-1,最大外部量子效率为 11.9%。即使亮度达到 5000 cd m-2 水平,外部量子效率 (EQE) 仍高达 10%,这表明器件效率在高电流密度下会缓缓下降。此外,通过纳米压痕技术,主 PCzMSi 薄膜通常能显示出良好的机械性能,以满足实际应用的需要。这些结果表明,设计基于聚硅氧烷的宿主材料是实现高性能溶液加工蓝色磷光聚合物发光二极管(PhPLED)的一种可行方法。