以蒽為主體之非晶態材料雙極性載子傳輸特性與摻雜電性研究及其在有機電激發光元件之應用

Abstract

將p型與n型有機摻雜層引入由2-methyl-9,10-di(2-naphthyl)anthracene (MADN) 天藍光系統與黃光材料rubrene所組成的雙波段白光有機電激發光元件結構中，並有效控制載子再結合區域於薄層發光層中，在亮度1000 cd/m2下可得到高發光效率10 cd/A和9.3 lm/W。利用有機摻雜層的p-n接面作為連接層，也可以製作出高亮度的串聯式雙波段白光有機電激發光元件。 但雙波段白光元件的色域與演色性無法達到全彩顯示器與固態照明應用的需求。於是我們開發出以2-methyl-9,10-di(1-naphthyl)anthracene (□,□-MADN) 為主發光體材料的高效率且穩定的深藍色發光系統並應用於三波段白光有機電激發光元件中，可得到高發光效率8 cd/A和寬廣的發光頻譜，CIE色度座標為(0.34, 0.35)，色域及演色性也提升到73.2 %和87。 我們也利用飛行時間量測法來量測一系列以蒽(anthracene)為主體的材料的載子傳輸特性，量測結果顯示這些材料具有極快的電洞載子遷移率，其數值介於2 × 10-3 to 9 × 10-3 cm2/Vs 之間。同時也發現能將C60應用於飛行時間技術中作為電荷生成層，可大幅減少樣品中待測材料的厚度。 另一方面， 根據導納量測理論與有機材料高阻抗的特性，我們提出了雙異質介面有機元件的導納等效電路模型，並用以研究MADN的p型與n型薄膜摻雜層電性。其結果顯示將氧化鎢(WO3)與氟化銫(CsF)摻雜於MADN中，可降低載子的注入能障以及元件的操作電壓。 最後，根據飛行時間量測法與導納分析的結果，我們設計出第一個以MADN為單一主體材料的高效率且穩定的有機電激發光元件。

We demonstrated highly power-efficient di-chromatic white organic light-emitting diode (WOLED) devices composed of a sky blue doped emitter of 2-methyl-9,10-di(2-naphthyl) anthracene (MADN) and a yellow emitter of rubrene. By introducing p-doped and n-doped organic layers into the device architecture along with carefully controlling the carrier recombination zone in a thin layer thickness, the high efficiency of 10 cd/A and 9.3 lm/W at 1000 cd/m2 can be achieved. A high-brightness tandem di-chromatic WOLED device with a connecting layer of organic p-n junction was also fabricated. But the color gamut and color rendering index (CRI) of di-chromatic WOLEDs are not adequate for full-color display and solid state lighting applications. Hence we developed an efficient and stable deep blue fluorescent system based on a host material of 2-methyl-9,10-di(1-naphthyl) anthracene (a,a-MADN) and adopted it to tri-chromatic WOLED devices. The color gamut and CRI of tri-chromatic WOLED device can be improved to 73.2% and 87, respectively, with high efficiency of 8.0 cd/A and a white CIEx,y coordinates of (0.34, 0.35). The hole mobilities of ADN-type material were also measured by time-of-flight technique, and it is found that ADN-type materials have high hole mobilities in the ranges of 2 × 10-3 to 9 × 10-3 cm2/Vs. C60 was also shown to be a useful charge generation layer and effectively reduces the layer thickness of test material for TOF measurements of hole mobilities of ADN-type materials. We further investigated the electrical characteristics of MADN-based p-doped and n-doped organic layers by measuring current-voltage curves and temperature-dependent admittance spectroscopy. It was found that the conductive-doping can reduce the injection barrier and drive voltage when they are adopted in OLED devices. Finally, according to all results disclosed in this thesis, an efficient and stable OLED device with simplified architecture based on a single common host of MADN was demonstrated for the first time with excellent performance.