應用複合式電洞傳輸層之高效率有機電激發光元件

Abstract

我們成功利用了CuPc捕捉與阻擋電洞的特性，搭配混摻電洞傳輸層之元件結構，開發出一新型電洞傳輸層(複合式電洞傳輸層)。藉由調整此電洞傳輸層內CuPc的摻雜濃度，可以有效的控制電洞在有機電激發光元件內的傳輸特性，達到載子平衡、提升元件發光效率的目的。

在綠光Alq3標準元件方面，套用複合式電洞傳輸層大幅的提升了元件發光效率達1.7倍，在20 mA/cm2電流密度下之最佳元件發光效率為5.96 cd/A，操作電壓為7.64 V。不但如此，應用複合式電洞傳輸層在藍光元件更有不錯的表現。例如在DSA-Ph為客發光體之天藍光元件，20 mA/cm2電流密度下之最佳元件發光效率為16.15 cd/A，操作電壓為6.44 V，CIEx,y色度座標為(0.15, 0.29)，不但不會對發光顏色造成任何影響，更有增加藍光色飽和度的效果。另外，在BD1為客發光體之深藍光元件，20 mA/cm2電流密度下之最佳元件發光效率為5.39 cd/A，操作電壓為6.79 V，CIEx,y色度座標為(0.14, 0.13)，與標準深藍光元件比較，發光效率提升約2倍。

Carrier recombination as well as the balance of holes and electrons is considered to be one of the most important factors that determine the luminance efficiency of OLEDs. In this study, a novel composite hole transport layer (c-HTL) has been developed, which can efficiently control the hole mobility in order to improve hole-electron balance. Improvement in the hole/electron recombination was illustrated by the remarkably high luminance efficiency.

Under 20 mA/cm2 current driven condition, the Alq3-based green device with c-HTL has achieved a luminance efficiency of 5.96 cd/A at 7.64 V, which is 1.7 times higher than that of the standard device. Furthermore, c-HTL has demonstrated even better performance in blue devices. The sky-blue OLED with c-HTL based on the DSA-Ph dopant in MADN host has achieved a luminance efficiency of 16.15 cd/A with a CIEx,y color coordinate of [0.15, 0.29] at 6.44 V (20 mA/cm2) without deteriorating on the color saturation. The deep-blue device with c-HTL based on the BD1 dopant in MADN host has achieved a luminance efficiency of 5.39 cd/A with a CIEx,y color coordinate of [0.14, 0.13] at 6.79 V (20 mA/cm2), which is approximately 2 time higher than that of the standard device.