Two highly fluorescent triphenylamines (TPA) end-capped respectively with one and three pyrene arms, namely N,N-diphenyl-4-(pyren-1-yl)aniline (PyTPA) and 4,4′,4′′-trispyrenylphenylamine (TPyPA), have been designed, synthesized and applied as hole-transporting emitters in organic light-emitting devices (OLEDs). While the two compounds have similar chemical structures (the only difference being the number of pyrene arms), devices based on them show distinct electroluminescent characteristics. PyTPA-based devices exhibit intense deep-blue emission with Commission Internationale de L'Eclairage coordinates (CIE) of (0.14, 0.11); whilst TPyPA-based devices emit white light with CIE of (0.31, 0.35). It is considered that the three electron-donating pyrene arms in TPyPA increase its electron-donating ability, which facilitates exciplex formation with the electron-transporter. This gives rise to a yellow exciplex emission and thus shifts the electroluminescence from deep-blue to white. More importantly, both devices can operate at record-low driving voltages (<4V at 20 mA cm−2), indicating the TPA-cored emitters offer not only high luminance efficiencies, but also good hole-injection and transporting features.
我们设计、合成了两种末端分别带有一个和三个
芘臂的高荧光
三苯胺(
TPA),即 N,N
-二苯基-4-(
芘-1-基)
苯胺(Py
TPA)和 4,4′,4′′-三
芘苯胺(TPyPA),并将其用作有机发光器件(OLED)中的空穴传输发射器。虽然这两种化合物具有相似的
化学结构(唯一的区别在于
芘臂的数量),但基于它们的器件却显示出截然不同的电致发光特性。基于 Py
TPA 的器件会发出强烈的深蓝色光,其国际照明委员会坐标(CIE)为(0.14, 0.11);而基于 TPyPA 的器件则会发出白光,其国际照明委员会坐标(CIE)为(0.31, 0.35)。据认为,TPyPA 中的三个电子负载
芘臂提高了其电子负载能力,从而促进了与电子传递器形成共轭物。这就产生了黄色的赋形剂发射,从而使电致发光从深蓝色转变为白色。更重要的是,这两种器件都能在创纪录的低驱动电压下工作(20 mA cm-2 时电压小于 4V),这表明
TPA 芯发光体不仅发光效率高,而且具有良好的空穴注入和传输特性。