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研究生:翁瑞興
研究生(外文):Ruey-Shing Weng
論文名稱:有機發光二極體在金屬與有機層界面的注入機制
論文名稱(外文):Injection Mechanisms at the Interface between Metal and Organic Layer in OLEDs
指導教授:翁恆義
指導教授(外文):Heng-Yih Ueng
學位類別:碩士
校院名稱:國立中山大學
系所名稱:電機工程學系研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2002
畢業學年度:90
語文別:中文
論文頁數:96
中文關鍵詞:有機發光二極體傳輸注入有機界面
外文關鍵詞:interfaceorganicinjectionLiFOLEDtransport
相關次數:
  • 被引用被引用:12
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  • 收藏至我的研究室書目清單書目收藏:2
在本論文中,將討論金屬電極與有機層間界面的界面電性與特性。由於目前文獻中,對於界面電性與載子在界面的注入過程並不真正地十分確定,所以在部分文獻中的元件模型,在處理載子的注入仍是以傳統的無機半導體為基礎。
當在Al與Alq3間插入一層薄的LiF層,OLED元件的performance有極大的改善,如降低驅動電壓、增加發光效率等。因此首先探討在金屬與有機層間加入一層非常薄的LiF 時,探討LiF對元件性能影響的可能機制。接著,針對關於載子在金屬與有機層間界面處的注入模型做進一步討論。最後,將討論LiF厚度變動時,與注入模型的關係。
關於LiF厚度變動參數對注入模型的影響,在實驗數據中,當LiF為0.5nm時,元件有最佳表現。而當LiF厚度大於0.5nm,元件表現逐漸變差。本論文假設當LiF厚度大於0.5nm時,單純只是由於LiF在此時形成一“完整的絕緣層薄膜”降低了載子的注入而使元件表現變差。而在推導過程中,假設與金屬功函數參數無關;且由於有機材料的分子結構與無機半導體的共價鍵晶格結構不同,因此假設平衡時在界面處無類似無機半導體p-n junction的能帶彎曲現象。最後得到的結果,與文獻所示相吻合。
因此經由本文理論推導與傳輸模型的模擬結果,證明載子的注入與金屬的功函數幾乎無關,而是由金屬與有機層間所形成的界面型態所決定。再者,對Al/LiF/Alq3架構,LiF在0.5nm時,其界面處的反應達到飽和;所以當LiF厚度大於0.5nm時,LiF在此時形成一“完整的絕緣層薄膜”,因此當LiF厚度大於0.5nm時,元件表現變差,其主要的原因是由於載子通過時,受到絕緣層的阻礙。
In this dissertation, the electrical characteristics of the interface between the metal cathode and organic layer in OLEDs are detailed investigated. Currently, surveying on the literature, it is limited in understanding the interfacial characteristics and the injection process of electron at interface, therefore the carrier injection phenomena investigated here is still based on the traditionally inorganic semiconductor physics.
As a thin LiF layer inserted between the Al and Alq3 layers, the performance of OLED shown a great deal of improvement, such as lowering the driving voltage and increasing the luminescence efficiency. At first, we study how a very thin LiF layer affecting the performance of OLED device, and the feasible mechanisms attributed to this improvements. Then, the further discussion should be focused on the injection model built for the charge at metal/organic interfaces. Finally, the relationship that the injection model related to the variety of LiF layer thickness could be investigated.
From the experimental data, the Al/LiF/Alq3 devices with the LiF thickness of 0.5nm have shown the best performance, and the device performance decay as the thickness of LiF layer increased over 0.5nm. In this study, it assumes that the LiF layer just forms an “integrated” thin insulating film and lowing the charge injection as the layer thickness over 0.5nm, and it also assume that in model derived process is independent on the metal work function.
Since the molecular structure of organic materials is quite difference from the valence band structure in inorganic semiconductor materials, it could be assumed no band bending like that the p-n junction at the interface of inorganic semiconductor under thermal equilibrium. After theoretical approach, we get the reasonable results by comparing with the literatures reported recently.
The conclusion of this study reveals that the charge injection is independent on the metal work function, but is determined by the interface structure characteristic of interface structure at metal/organic interfaces. Furthermore, in the Al/LiF/Alq3 structure, the chemical reaction is saturated at the interface as the LiF layer forms a “integrated” thin insulating film. Therefore, the device performance decay is the effect due to the insulating LiF layer when the thickness of LiF layer is over 0.5nm.
第一章緒論...........................................1
第一節有機發光二極體的介紹..................1
1.1.1 OLED與平面顯示器簡介.....................1
1.1.2 OLED的發展概況...........................2
1.1.3 小分子與高分子OLED的比較.................3
第二節有機發光二極體的工作原理..............5
1.2.1 螢光與磷光...............................5
1.2.2 有機電致發光與染料的摻雜.................5
1.2.3 OLED元件架構.............................6
1.2.4 多彩、全彩OLED元件架構...................8
第三節論文目的與章節簡介....................9
第二章文獻討論......................................10
第一節陰極電極的演進.......................10
第二節陰極/有機層間的界面電性特性..........12
第三節陰極/有機層間注入模型的討論...........17
2-3-1 空間電荷限制與注入限制傳輸...............17
2-3-2 界面傳輸模型(一).........................20
2-3-3 界面傳輸模型(二).........................26
第三章模型推導與討論.................................29
第一節條件..................................29
第二節考慮MIS穿透二極體的模型,與方形能障的穿透率....31
第三節考慮載子的分佈.........................33
第四節討論...................................35
第四章結論............................................39
Reference................................................40
圖表.....................................................46
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