倒置式上發光有機電激發光二極體元件電子注入層之研究

Abstract

為了與n型薄膜電晶體結合應用至廣色域的有機電激發光顯示器上，我們致力於研發倒置式上發光有機發光二極體。在我們倒置式上發光結構的研究中，鍍上高反射的Al金屬作為陰極，以Ag和2.5 nm 的Al加17.5 nm 的Ag的半穿透薄膜作為陽極能夠得到最佳的增益強度。我們開發出了新型以Alq3-LiF-Mg為電子注入層的元件。金屬Mg的最佳化厚度比使用傳統Alq3-LiF-Al電子注入層的元件金屬Al最佳化厚度要薄，較適合應用在ITOLED元件上。且電性上與BPhen: 5% Cs2CO3作為n型摻雜層的電子注入層的元件上差不多，並且擁有較好的元件穩定性。以單層WO3 （5 nm）的電洞注入層搭配半穿透陽極Al/Ag以降低電洞從陽極注入的能障，應用此結構的綠光螢光ITOLED有效的降低了載子注入的能障，提高元件的效率，而此結構的倒置式Alq3綠光上發光元件效率可達6.0 cd/A，且較高飽和度CIEx.y = (0.22,0.67)。

Inverted type OLEDs have become increasingly important and timely for the realization of n-channel a-Si or Oxide TFT driven large panel active-matrix OLED displays. We developed inverted top-emission OLED employing highly reflective Al as cathode and a semitransparent Al/Ag as anode on glass substrate by using hole injection layer (tungsten oxide, WO3) to alleviate the severe energy level mismatch between anode and organic layer. We discovered a novel trilayer [Alq3-LiF-Mg] as the electron injection layer (EIL) in which its optimized metallic Mg component is thinner than the metallic Al in the conventional [Alq3-LiF-Al] electron-injection triad structure. This new EIL was demonstrated in an inverted top-emitting OLED (ITOLED) of green fluorescent Alq device which achieved an efficiency of up to 6.0 cd/A with a saturated CIEx,y coordinate (0.22, 0.67). The current density–voltage characteristic of this ITOLED is similar to the device with BPhen: 5% Cs2CO3 as n-type doped EIL, and its operational lifetime is also more stable.