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標題: | 高效率有機發光材料與元件之光電特性與可靠度探討 Investigation of optoelectronic properties and reliability of high-efficiency organic light-emitting materials and devices |
作者: | Yi-Jiun Shiu 徐宜君 |
指導教授: | 吳忠幟 |
關鍵字: | 有機發光二極體,硼錯合物,熱激活化延遲螢光,濕製程,元件可靠度,磷光元件,電荷平衡, OLEDs,Boron complexes,thermally activated delayed fluorescence,solution process,operation lifetimes,reliability,phosphorescence OLEDs,charge balance, |
出版年 : | 2018 |
學位: | 博士 |
摘要: | 有機發光二極體已成為重要的顯示技術與照明技術,因此元件的效率與壽命備受重視。第三代OLED材料熱激活化延遲螢光(Thermally Activated Delayed Fluorescence, TADF)經由分子結構的設計可開發內部量子效率具有潛力達理想100%,此種技術無需使用較昂貴之稀有過度金屬元素,以純有機之分子結構但仍能達到高效率,更能落實低成本高效率並符合經濟效應。因此本論文第一部分主要研究具前瞻性之TADF發光材料,並對於其物理機制進行深入探討,再透過光學優化的結構設計將元件效率達到理論極限。此外,有機發光二極體的壽命亦為現行OLED應用瓶頸之一,因此如何透過元件結構設計而達到元件內部電荷平衡及可靠度是一個重要課題;本論文第二部分針對綠藍磷光發光材料及元件進行可靠度研究,針對材料能階匹配及電洞/激子阻擋層的採用以及複合區的議題進行一系列元件內部電荷平衡並提升元件壽命的探討。
首先,本論文研究一系列新穎含硼化合物的TADF發光材料,以硼原子為主體的化合物可促使donor與acceptor呈正交結構,進而得到較小的單重態及三重態的能階差(),本研究探討其TADF光物理特性(吸收/放光頻譜、暫態時間解析等),並以濕製程方式製作OLED元件得到外部量子效率13.5%的綠光元件。 其次,接續前部份研究,經由材料結構改良後,增加材料本身的熱穩定性質,衍生出另一系列新的含硼化合物TADF材料,經由改變不同的donor而得到藍-綠光的硼化合物,此系列綠光TADF材料經由深入的光物理特性分析後發現不僅具有TADF特性且大幅提升內部量子效率,並能以熱蒸鍍方式製作元件並透過光學優化元件後,可得外部量子效率近27%的高效率TADF綠光元件。 論文最後部份探討磷光OLED元件內各種因素對於可靠度的影響。藉由選擇具有較好的熱穩定性/化學穩定性材料、元件各層材料間能階匹配、及三重態能階之侷限能力與增加再結合區的區域範圍,幫助元件內部達到電荷平衡且有助於提升元件效率及壽命。 Organic light-emitting diodes (OLEDs) have attracted much attention due to their applications for displays and lighting. To enhance OLED performances and reduce cost for displays and lighting, the third-generation OLED materials, thermally activated delayed fluorescence (TADF) materials, have emerged in recent years. Through the design of the material structures, TADF materials are in principle able to achieve 100% IQE without using more expensive heavy metal elements. In the first part of this thesis, we studied a series of novel boron based TADF materials and their use for high-efficiency TADF OLEDs. On the other hand, OLED stability also remains an important issue nowadays. In the second part of this thesis, we investigated OLED reliability through considering the charge balance and other issues. First, we studied TADF materials exploiting the boron atom as a hub to anchor both electron-donating and electron-accepting moieties, for which the poor orbital overlap between donor and acceptor provide the needed criteria for reduced . These novel TADF complexes show intense luminescence accompanied by prominent TADF. Among all studied OLEDs, the device using PrFTPA processed by spin coating achieved EQE of 13.5 %. The results demonstrate that boron complexes can be used as a core composite to attain high performance OLEDs via harvesting TADF, broadening the horizon of the TADF class of molecules. Second, we studied another new series of TADF boron complexes (including fppyBTPA and dfppyBTPA) whose thermal stabilities are much better than the materials in the first part. The electron-donating triphenylamine and the electron-accepting functional phenyl-pyridinato fragment are linked at a boron bridge in fppyBTPA and dfppyBTPA. We obtained efficient green TADF OLEDs with external quantum efficiency (EQE) nearly 27% by vacuum evaporation. Third, we investigated operational lifetimes of phosphorescent OLEDs, to study the relation between device reliability, charge balance, energy level, triplet energy confinement and recombination zone. Through this study, we reported a relatively stable device structure, which can achieve better charge balance, and relatively maintained EL efficiency, and prolonged operational lifetime. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/77449 |
DOI: | 10.6342/NTU201804286 |
全文授權: | 未授權 |
顯示於系所單位: | 電子工程學研究所 |
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