| 研究生: |
余昀澔 Yu, Yun-Hao |
|---|---|
| 論文名稱: |
主鏈含孤立發光及電子傳遞基團高分子的合成與光電性質 Luminescent Copoly(aryl ether)s Consisting of Alternate Emitting and Electron-Transporting Segments Derivatives: Synthesis and Characterization |
| 指導教授: |
陳雲
Chen, Yun |
| 學位類別: |
碩士 Master |
| 系所名稱: |
工學院 - 化學工程學系 Department of Chemical Engineering |
| 論文出版年: | 2003 |
| 畢業學年度: | 91 |
| 語文別: | 中文 |
| 論文頁數: | 117 |
| 中文關鍵詞: | 光電性質 、孤立發光基團 、發光二極體 |
| 外文關鍵詞: | electron-transporting segment, emitting segment, PLED |
| 相關次數: | 點閱:64 下載:1 |
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高分子發光二極體(Polymer Light Emitting Diode, PLED)利用電激發光的原理,在PLED元件施加一順向偏壓後,電子與電洞分別由陰極與陽極注入,因為外加電場所造成的電位差,使得載子在有機薄膜中移動,進而在發光層中再結合形成電子-電洞對的激子,當此激子釋放能量後回到回基態時,部分能量會以光子的方式放出,使PLED元件發光。為了提高發光效率,必須減少電極與高分子間的能障及平衡電子電洞注入的速率來提高電子與電洞再結合的機率,大部分PLED高分子電洞注入速率大於電子,所以可利用多層結構導入電子傳遞層(Electron Transport Layer, ETL),或是摻混電子傳遞分子,或是利用化學合成改變分子結構,來提升電子注入的能力。
本研究合成主鏈含孤立發光基團及電子傳遞基團的高分子,在結構上以二苯乙烯衍生物為發光基團,並導入具電子傳遞功能的Oxadiazole基團,利用親核性取代反應合成具芳香醚高分子,使其共軛長度受到控制,並提升電子注入的能力。所合成的高分子P1~P5皆有良好的熱穩定性。利用模式化合物與高分子的比較,P1~P4的螢光光譜皆有能量轉移的現象,使高分子的發光及螢光量子產率皆由發光基團所控制,P1、P2發藍光,P3、P4發藍紫光。利用CV求得其氧化還原起始電位,並求出高分子的HOMO與LUMO能階,導入電子傳遞基團的P1~P4其LUMO能階都有明顯的下降,表示其改善了電子注入的能力。元件方面,比較所合成的高分子P2與摻混元件及雙層元件,將電子傳遞基團以化學方法導入主鏈的高分子P2其元件性質最佳,但由於孤立系統分子主鏈上是非全共軛的結構,使載子在分子鏈上移動較為困難,減少再結合的機率,所以造成元件的亮度並不高。
PLED have attracted much interest in recent years due to their potential application in large-area flat panel displays. To achieve high EL efficiency, it is necessary to balance the injection rates of opposite charges and decrease the barriers of charge injection from the opposite contacts. To achieve balanced charge injection, metal electrode with low work function and additional electron transporting layer have been widely employed. Besides, introducing electron transporting units in polymer structure can also be employed to balance charge injection.
In this work, four isolated copolymers including emitting segments (distyrylbenzene derivatives) and electron-transporting segments (1,3,4-oxadiazole derivatives) were synthesized and characterized. The ether spacers limited the π-conjugation length to allow the polymers to emit the fixed light color. The emission and the PL quantum yield of the polymers were dominated by the fluorophores with longer emissive wavelength via energy transfer from electron-transporting segments. The HOM and LUMO energy levels of these polymers have been estimated from their cyclic voltammograms. The electron affinity can be enhanced by introducing isolated electron-transporting segments that lead to charges injection balance. In single layer LED devices [Al/polymers (P1~P5)/ITO glass], incorporation of bis-oxadiazole unit increases the electron affinity and reduces the turn-on electric field better than one oxadiazole unit and the optoelectronic properties were better than P5 without electron-transporting segment. Moreover, incorporation of electron transporting segment in P2 leads to better optoelectronic properties than other methods such as blending and double layer devices.
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