上發光有機發光二極體之陽極研究

The study of Top-Emission Organic Light Emitting Diode Anode

蔡承儒(Cheng-Ru Tsai)

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2006年)

摘要

本論文研究上發光型有機發光二極體之陽極，共分成三個部份：1.以Al/Ag/Ag2O為陽極 2.以Al/Au為陽極 3.以Al/AuGeNi為陽極 製作上發光有機發光二極體元件。第一部份利用UV-ozone來製作Ag2O，使陽極功函數提高，有效改善電洞注入效果。利用高反射金屬Al，搭配高功函數金屬， Au，來作為高反射陽極。Al/Au雙層金屬層作為元件陽極可以有較佳的發光特性。隨後研究Al/Au陽極中Al和陰極Ag最佳厚度調整，當Al 60/Au 2 nm時，能夠具有高反射率，且與有機層有最佳電洞注入特性，提升發光效能。陰極方面選用多層金屬複合層LiF/Al/Ag作為陰極，同時亦探討其最佳厚度，以兼顧陰極穿透性及導電性。當陰極厚度為LiF0.2/Al 2/Ag 15 nm，可以有較佳穿透性及不錯的導電性，使發光特性提升。最後有效調整有機層厚度使元件發光特性達到最佳化。第三部份利用高反射金屬Al，搭配其他高功函數合成金屬，如AuSn, AuGe, AuGeNi等，來作為高反射陽極。發現Al/AuGeNi雙層金屬層作為元件陽極可以有較佳的發光特性。最後針對有機層方面研究改變電洞注入層、電洞傳輸層及電子傳輸層三者之間厚度最佳控制，當有機層厚度為m-MTDATA 30/NPB 10/Alq3 100 nm時，可得到最佳發光效率1.4 cd/A，最高亮度3010 cd/m2。

並列摘要

The top emission organic light-emitting diodes (TEOLEDs) with multilayer electrodes were studied. A high-reflectivity bottom anode is essential for high-performance top-emitting organic light-emitting devices. Ag has the highest reflectivity for visible light among all metals, yet its electronic properties are not ideal for anodes of OLEDs. We report that by inducing a thin silver oxide at the surface of Ag, hole injection from Ag anodes into OLEDs is largely enhanced yet with rather high reflectivity retained. Top-emitting devices using such surface-modified Ag anode show device characteristics competitive with those of a bottom-emitting device using the indium tin oxide anode. Firstly a high reflectivity metal, Al, followed by a high work function metal, such as AuSn、AuGe or AuGeNi, was used as bilyaer anode. It was found that the Al/Au bilayer anode can give rise to a very good luminescent performance if the Al thickness in the bilayer was adjusted to 60 nm. The Al/AuGeNi bilayer anode has high reflectivity and good adhesive contact with the hole injection layer. Next the cathode in TEOLEDs composed of multiple layers, LiF/Al/Ag, were studied. The optimum thicknesses in each layer as 0.2/2/15 nm were used to achieve high transparency and good conductivity. The effects of thicknesses of each organic layer were also studied. When the optimum thicknesses of m-MTDATA/NPB/Alq3 were adjusted to 30/10/100 nm, the highest brightness and best luminance efficiency of 3010 cd/m2 and 1.4 cd/A, respectively, were obtained.

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