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研究生:朱健慈
研究生(外文):Chien-Ci Chu
論文名稱:具有雙載子傳輸層之藍光有機發光二極體研究
論文名稱(外文):A Study of Blue Organic Light Emitting Diodes with Bipolar Transport Layers
指導教授:橫山明聰蘇水祥
指導教授(外文):Meiso YokoyamaShui-Hsiang Su
學位類別:碩士
校院名稱:義守大學
系所名稱:電子工程學系
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:英文
論文頁數:90
中文關鍵詞:有機發光二極體有機藍光雙載子傳輸
外文關鍵詞:OLEDorganicbluebipolar transport
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在本篇論文中,我們可以藉由雙載子傳輸發光層減少電洞累積在介面及增加電子注入到發光層。雙載子傳輸發光層元件的結構為ITO/NPB/BTEL(NPB:CuPc)/BCP/Alq3/Al。ITO、NPB、BTEL、BCP、Alq3、Al分別為陽極、電洞傳輸層、發光層、電洞阻隔層、電子傳輸層及陰極。雙載子傳輸發光層是由NPB及CuPc利用共蒸著的方式所組成,這個結構可以增加電子注入到發光層,平衡電子和電洞的數目,而且可以減少電洞累積在介面。首先我們探討藉由改變雙載子傳輸發光層的混合比例及厚度對元件特性的影響,實驗結果顯示,當元件結構ITO/NPB(10nm)/BTEL(20nm)/BCP(15nm)/Alq3 (25nm)/Al ,且BTEL中NPB和CuPc的混合比例為10比1,元件壽命可以提昇3倍以上,亮度也可以增加2倍。
接下來我們將NPB及CuPc共蒸著的方式改為多層的結構來分散累積在介面上的電洞數量,這個多層量子井元件的結構為ITO/(NPB/CuPc)n/NPB/BCP/Alq/Al。在這裡n從0到6做調變,我們經由改變NPB和CuPc的厚度比例,來探討多層量子井元件的特性變化,由實驗結果顯示,當元件結構為ITO/[NPB(5.4nm)/CuPc(0.75nm)]4/NPB(5.4nm)/BCP(15nm)/Alq3 (25nm) /Al ,元件的亮度及效率可以提高2倍。可知多層量子井的結構可以平衡電子和電洞在發光層的數量進而提高發光的效率。從本篇論文中可以很明顯的發現利用雙載子傳輸發光層和多層量子井的結構可以改善藍光有機發光二極體的特性。

In this study, we could reduce the holes accumulated in the interface and enhance electrons injection into emission layer by using bipolar transport emission layer (BTEL). The structure of BTEL OLEDs is ITO/NPB/BTEL(NPB:CuPc)/BCP/Alq3/Al. ITO is used as an anode and NPB、BTEL、 BCP、Alq3、Al are used as a hole transport layer (HTL), an emission layer (EML), a hole blocking layer (HBL), a electron transport layer (ETL), and a cathode, respectively. The BTEL layer consists of NPB and CuPc, and is prepared with co-evaporation. This structure could enhance the electrons injection into the emission layer to balance the amount of holes and electrons, and reduce the hole accumulation in the EMT/HBL interface. First, We investigate the characteristics of BTEL OLEDs with various ratio and thickness in BTEL layer. Experimental results show that a BTEL OLED with the structure of ITO/NPB(10nm)/BTEL(20nm)/BCP(15nm)/ Alq3 (25nm)/Al[NPB:CuPc=10:1] exhibits good optoelectrical characteristics. The lifetime of an OLED with BTEL is three times than without BTEL, and the brightness is improved by two times.
Secondly, NPB/CuPc mult-layer is used in OLEDs structure to separate the holes in the EML/HBL interface. The structure of multiple-quantum-well (MQW) OLEDs is ITO/(NPB/CuPc)n/NPB/BCP/Alq3/Al. n is varied from 0 to 6. Varying the thickness ratio of NPB and CuPc, and investigation the characteristics of MQW OLEDs. The optimum structure is ITO/[NPB(5.4nm)/CuPc(0.75nm)]4 /NPB(5.4nm) /BCP(15nm)/Alq3(25nm)/Al(200nm), The brightness and efficiency of an OLED with a MQW structure is two times than without MQW. The structure of MQW could balance the amount of holes and electrons in the emission layer to improve luminance efficiency. Obviously, there are rather improvements of blue organic light emitting diodes performance by using either bipolar transport emission layer, or NPB/CuPc multiple-quantum-well structures.

Content
Abstract (in Chinese) i
Abstract (in English) iii
Acknowledgement v
Content vi
Table Captions ix
Figure Captions x
Chapter 1 Introduction
1-1 The history of organic light emitting diodes 1
1-2 The comparison of all displays 2
1-3 The aim of this study 3
Chapter 2 Review of Literatures
2-1 Principles of Luminescence 4
2-1-1 The Characteristics of Absorption and Emission 5
2-1-2 Characteristic Absorption of Organic Compounds 7
2-2 Physics of Operation 8
2-2-1 Characteristics of Charge Injection and Transpor 10
2-3 The structure of OLED 11
2-3-1 Electrode 11
2-3-2 Hole-Blocking Layer 13
2-4 Degradation of OLED 13
2-4-1 Joule Heating 14
Chapter 3 Experimental Procedure
3-1 Material 17
3-2 Substrate Etching and Cleaning 17
3-3 Vacuum evaporation system 18
3-4 Deposition of organic thin films 19
3-5 Deposition of electrodes 20
3-6 Measurement 20
3-6-1 Photoluminescence spectroscopy 21
3-6-2 Electroluminescence spectroscopy 21
3-6-3 Current-voltage measurement 22
3-6-4 Luminance measurement 22
3-6-5 CIE measurement 22
3-6-6 Ultraviolet-visible spectroscopy (UV-Vis) 23
3-6-7 Luminous efficiency 23
3-6-8 External quantum efficiency 24
Chapter 4 Results and Discussion
4-1 The Blue OLEDs with Various Ratio and Thickness of BTEL 26
4-1-1 BTEL mixed ratio is 5:1 and vary different thickness 26
4-1-2 BTEL mixed ratio is 10:1 and vary different thickness 27
4-1-3 BTEL mixed ratio is 25:1 and vary different thickness 28
4-1-4 Stability of BTEL OLEDs 28
4-2 Multi-layer with NPB and CuPc 29
4-2-1 Thickness ratio of NPB and CuPc is 4:1 30
4-2-2 Thickness ratio of NPB and CuPc is 9:1 31
Chapter 5 Conclusions and Future Prospects
5-1 Conclusions 33
5-2 Future Prospects 34
References 35

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