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標題: | 熱激活化延遲螢光材料之有機發光元件應用 Applications of Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Devices |
作者: | Meng-Jung Wu 吳孟融 |
指導教授: | 吳忠幟(Chung-Chih Wu) |
關鍵字: | 熱激活化延遲螢光,非摻雜元件,主體材料,白光元件,輔助性摻雜, TADF material,non-doped organic light emitting devices,host material,WOLEDs,Assistant dopant, |
出版年 : | 2016 |
學位: | 碩士 |
摘要: | 有機發光元件至今已經快速發展成一具有潛力的平面顯示技術,近幾年,熱激活化延遲螢光 (TADF) 材料引起廣泛討論,以其為發光體的元件在紅、綠、藍各式光色中,都達到足以和磷光匹敵的高效率 (EQE>20%)。熱激活化延遲螢光 (TADF) 材料最大的特性,在於其利用逆系統間跨越 (T 1 →S 1) 的過程,可同時蒐集單重態和三重態的激子,減少能量損失。此外,TADF材料還具有低價格、豐富來源和簡易的材料製備等特性,而儼然成為下一代OLED顯示技術材料的首要候選者。在我的論文中,欲利用TADF材料的現象,嘗試除了在擔任摻雜發光體以外,在其他功能上的利用。
我們實驗室已經發表以SpiroAC-TRZ的neat film特性可達到~100%的PLQY,為具有良好特性的TADF材料。在論文的第一部分,我們製作了以純SpiroAC-TRZ為發光層的非摻雜元件。我們設計單、雙、三和四層有機結構元件,改變不同電洞傳輸層和電子傳輸層材料,得到最佳結構為四層有機材料結構,具有低的起始電壓、好的注入電流,和相當高的EQE ~15%。 在論文的第二部分,我們以SpiroAC-TRZ當主體材料,在其中摻雜綠光磷光材料Ir(ppy)2acac,得到了優異的結果,操作電壓極低,EQE= 26.5%,元件roll-off很小,在10000 cd/m2下只有下降到EQE= 25.4%。由於TADF材料分子結構包含電洞傳輸材料和電子傳輸材料的單元,具有良好的雙極性傳輸特性,也具有成為良好主體材料的潛力。 在論文的第三部分,我們以mCPCN為主體材料,SpiroAC-TRZ為輔助性摻雜,TBRb為摻雜的黃光螢光材料,藉由調變兩者摻雜濃度的比例,觀察其頻譜變化。結果得到,在TBRb低濃度 (~0.5wt%) 參雜下,可以得到由SpiroAC-TRZ輔助轉移的能量,放出黃光,且SpiroAC-TRZ本身也會放天藍光,得到雙峰值發光元件(EQE~20%),CIE 座標位置為 (0.31, 0.44),為現今以全螢光為主的少數高效率白光元件。 Organic light-emitting devices (OLEDs) have been developed as an important display technology. In the past few years, thermally activated delayed fluorescence (TADF) materials have been developed to produce efficient fluorescence through harvesting both singlet and triplet excitons, by effective reverse intersystem crossing (T 1 →S 1). When applied as doped emitters, their OLED performance (EQE > 20%) can be comparable with phosphorescent emitters. Actually, TADF devices have already made great progresses in red, green, and blue OLED efficiency. Features such as low cost, rich resources and easy material preparation promote TADF materials as the most promising candidate for next-generation full-color OLED materials. In my thesis, we tried to take the advantages of the TADF phenomenon and use TADF materials in multifunctional applications. Our group has already reported that the TADF material, SpiroAC-TRZ, can yield a highly efficient TADF neat films having nearly unitary (~100%) PLQY. In the first part of the thesis, we fabricated non-doped organic light emitting devices by utilizing pure SpiroAC-TRZ as the emitting layer. We tested devices structures with single, double, three to four organic layers. By varying HTL (hole transport materials) and ETL (electron transport materials), we obtained the best results in four-layers devices with good characteristics such as low turn-on voltage, high current density, and high external quantum efficiency (~15%). TADF materials in general have bipolar carrier transport capability, due to both donor and acceptor units in their chemical structures. In the second part of the thesis, we used optimized non-doped SpiroAC-TRZ device structure as host for green Ir(ppy)2acac phosphorescent dopant. Such green phosphorescent OLED showed high external quantum efficiency (~26.5%) and low drive voltage. Most importantly, the device exhibited low efficiency roll-off (e.g. EQE~ 25.4% for a brightness of 10000 cd/m2). In the third part of the thesis, we utilized SpiroAC-TRZ as the TADF assistant dopant and the TBRb yellow fluorescent emitter as the sensitized emitter in the emitting layer. It resulted in efficient WOLEDs which can achieve high external quantum efficiency (~20%) and CIE coordinate at (0.31, 0.44), which is among the most efficient WOLEDs using all fluorescent materials. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/76729 |
DOI: | 10.6342/NTU201601540 |
全文授權: | 未授權 |
顯示於系所單位: | 光電工程學研究所 |
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