Fluorinated 9,9′-spirobifluorene derivatives as host materials for highly efficient blue organic light-emitting devices
作者:Zhanfeng Li、Bo Jiao、Zhaoxin Wu、Peng Liu、Lin Ma、Xiaoli Lei、Dongdong Wang、Guijiang Zhou、Huaiming Hu、Xun Hou
DOI:10.1039/c3tc00466j
日期:——
A series of new fluorinated 9,9â²-spirobifluorene derivatives (SFs) have been designed and synthesized for organic light-emitting devices (OLEDs). The spatial structure of 2,2â²,7,7â²-tetrakis(2,4-bifluorophenyl)spiro-9,9â²-bifluorene was determined by X-ray diffraction analysis. With the different substitution patterns of electron-withdrawing groups, such as F and CF3, the photophysical properties, energy levels and thermal stabilities of these SFs can be tuned, which is supported by density functional studies of their geometries and electronic structures. A non-doped deep blue OLED using 2,2â²,7,7â²-tetrakis(3-fluorophenyl)spiro-9,9â²-bifluorene (Spiro-(3)-F) as the emitter shows excellent Commission Internationale de l'Ãclairage (CIE) coordinates of (0.169, 0.122) with emission peaking at ca. 408 nm. Furthermore, these SFs serve as an excellent host material for the 4,4â²-bis(9-ethyl-3-carbazovinylene)-1,1â²-biphenyl dopant to form high-performance OLEDs with low turn-on voltages and high efficiencies, especially for Spiro-(3)-F as the fluorescent host with pure blue CIE coordinates of (0.149, 0.187), a low turn-on voltage of 3.4 V, high luminance of over 10â000 cd mâ2, a high current efficiency of 6.66 cd Aâ1, and a high external quantum efficiency of 4.92%. The high efficiency is attributed to the high carrier mobility together with the low injection barriers for both the electron and the hole in the Spiro-(3)-F-based device.
为有机发光器件(OLED)设计并合成了一系列新的含氟 9,9â²-螺二芴衍生物(SFs)。通过 X 射线衍射分析确定了 2,2â²,7,7â²-四(2,4-二氟苯基)螺-9,9â²-二芴的空间结构。通过不同的取电子基团(如 F 和 CF3)取代模式,这些 SFs 的光物理特性、能级和热稳定性可以得到调整,其几何和电子结构的密度泛函研究也支持了这一点。使用 2,2â²,7,7â²-四(3-氟苯基)螺-9,9â²-二芴(Spiro-(3)-F)作为发射体的无掺杂深蓝色有机发光二极管显示出卓越的国际照明委员会(CIE)坐标(0.169, 0.122),其发射峰值约为 408 nm。408 纳米。此外,这些 SFs 还是 4,4â²-双(9-乙基-3-咔唑乙烯)-1,1â²-联苯掺杂剂的绝佳宿主材料,可形成低开启电压和高效率的高性能有机发光二极管,尤其是作为荧光宿主的螺-(3)-F,其纯蓝色 CIE 坐标为(0.149, 0.187),开启电压低至 3.4 V,亮度高达 10,000 cd mâ2 以上,电流效率高达 6.66 cd Aâ1 ,外部量子效率高达 4.92%。高效率归功于史派隆-(3)-F 器件的高载流子迁移率以及电子和空穴的低注入势垒。