刮刀塗佈技術製作有機發光二極體之壽命研究

Abstract

影響OLED壽命衰退的因子，可區分為內在和外在兩種。而造成外在因子的最大來源就是環境中的水氧，由於OLED有機材料與高活性金屬陰極對於環境中的水氧皆相當敏感，受水氧侵蝕的位置當OLED通電時即呈現不發光的黑點，而黑點會隨著時間的增長而慢慢變大，使得真正發光的區域越來越小，造成OLED亮度衰退的現象。本篇論文首先透過改良的封裝條件，包括：新型封裝膠、噴砂封裝玻璃、吸濕劑以及封裝置具，完全抑制OLED元件黑點的生長來源。 然而，仍可以發現OLED的亮度還是隨著操作時間增長而產生衰退現象。而這樣的衰退機制，就要歸咎於OLED本身元件結構或是所使用的有機材料上，因此，這些就稱之為內在因子。本篇論文是以綠光磷光元件(ITO/PEDOT:PSS/TcTa/26DCzPPy:Ir(mppy)3=94:6/TPBi/LiF/Al)為基準，嘗試改變HTL、Host材料、添加PFI (perfluorinated ionomer)改變電洞注入層功函數、發光層使用mixed host系統，在定電流的情況下，亮度以1000 nits為起始點，去觀察元件亮度的變化，最後發現mixed host系統較能有效的改善元件壽命。

There are two factors affecting the lifetime of OLED, divided into intrinsic and extrinsic types. The largest source of extrinsic factor is the moisture and oxygen of environment. Since highly active metal cathode and the organic materials in OLED are quite sensitive to moisture and oxygen, these parts will be eroded easily. When the current through the OLED, the parts which were eroded will not light and showing black spots. As time becomes longer, the black spots become larger and light parts become smaller,it makes OLED's brightness decline. In this thesis, we use improved encapsulation conditions to inhibit the growth sources of black spots in OLED, such as new glue、sandblasting glass、getter and encapsulation device. However, we still find that the brightness of OLED declines with time. The reason for this phenomenon is caused by the organic materials or the device structure, and these are the intrinsic factors. In this thesis, we use green PHOLEDs (ITO/PEDOT:PSS/TcTa/26DCzPPy:Ir(mppy)3=94:6/TPBi) as the standard, and using some methods, such as change HTL、Host material，add PFI(perfluorinated ionomer) to change HIL work function, EML use mixed host system. We observed the brightness changes under the constant current and setting the starting point of brightness as 1000 nits, and finally, we found that the mixed host system can improve the lifetime of the devices effectively.