臺灣博碩士論文加值系統

白光有機發光二極體(White OLED)由於可應用於液晶顯示器(LCD)的背光源以及照明光源…等用途，因此極具有研究發展的必要與急迫性，包含它的發光特性、對比度、色純度都有極大的改良空間。因此，本論文將以白光OLED搭配銥(Ir)金屬複合物且結合緩衝層與抗反射層改善其光電特性，藉以完成高效率白光OLED元件的最佳組成結構設計與光電特性分析。
第一部份，本論文將先針對OLED的電洞注入特性進行分析與探討。首先本論文探討不同的ITO蝕刻方式進行分析與探討，由實驗結果發現利用雷射(Laser)蝕刻的OLED元件比傳統濕式(Wet)蝕刻具有較小的驅動電壓，然而雷射蝕刻的OLED元件發光特性卻變差，其原因乃由於利用雷射蝕刻的ITO圖樣在圖形邊界處會有一突起物導致高的電場存於邊界處，進而使OLED元件的發光特性及穩定性變差。接著本論文在電洞注入層(PEDOT:PSS)內加入奈米級二氧化鈦(TiO2)微粒藉由改善其光電特性，由實驗結果發現加入TiO2可使ITO與PEDOT:PSS層之間的能障降低，以致改善元件的光電特性，且改變發光頻譜的半高寬，此乃由於TiO2造成的光散射所致。繼續本論文創新的利用無機半導體材料硒化鋅(ZnSe)作為OLED的電洞注入(緩衝)層，實驗發現加入適當厚度的ZnSe可有效改善OLED的發光效率。當ZnSe緩衝層的厚度在7.5Å時，可獲得最高發光效率。
第二部份接著利用CuPc與TiOPc作為電子傳導層暨抗反射層進而改善OLED的對比度。實驗結果發現，加入CuPc與TiOPc作為電子傳導暨抗反射層可有效改善OLED的對比度約為2倍，而且在OLED元件的發光效率部分不但沒有因為抗反射層的損失，反而高於傳統元件。
最後，本論文探討具銥複合物之白光OLED的光電特性及其發光機制。由實驗結果發現良好的TPBI發光與Ir(ppy)3和Ir(piq)2(acac)的複合物及吸收頻譜重疊使得主體材料TPBI可以有效地將能量轉換給銥金屬複合物，進而得到高的發光效率。此外我們將具有銥金屬複合物的白光OLED加入ZnSe作為緩衝層以及CuPc與TiOPc作為電子傳導與抗反射層，藉由上述結構完成約2倍的高對比度之具有銥金屬複合物的白光OLED。

Owing to the urgent marketing requirement in LCD backlight and illumination light sources fabricated by white organic light emitting diode (OLED), more studies engaged in the luminescent performance, driving voltage, contrast and color purity of white OLED are still needed. Therefore, the main purpose of this doctoral thesis is to improve the optoelectronic properties of white OLED with iridium complexes and accomplish the optimal design for fabricating the structured white OLED as well as its optoelectronic characteristics analyses.
We reported an investigation of the hole injection properties of organic light-emitting diodes. The effect of laser and wet etching methods of ITO substrates on the optoelectronic properties of OLEDs was investigated. We found that the OLED with a laser-etched ITO substrate has a lower driving voltage than that with a wet-etched ITO substrate. However, a laser-etched ITO substrate worsens the luminance of an OLED. This lower luminance is attributed to the shoulder at ITO/glass fringe, which is responsible for a high local electric field. Besides, OLEDs with a light scattering layer are proposed and their optoelectronic characteristics have been investigated. TiO2 was doped into the PEDOT:PSS layer to as a light scattering layer. The TiO2 could act as a buffer to decrease the barrier high between ITO and PEDOT:PSS interface. On the other hand, high efficiency OLEDs with a ZnSe semiconductor layer as hole-injection semiconductor buffer has been fabricated. The device with a 7.5 Å thickness semiconductor buffer layer has the best power efficiency.
Moreover, we also investigated an high contrast ratio and high power efficiency OLEDs using dual electron transporting layer of copper phthalocyanine (CuPc)/ titanium oxide phthalocyanine (TiOPc) as an anti-reflection layer. The contrast ratio of the device with a CuPc / TiOPc anti-reflection layer is about double and the power efficiency higher than that of a conventional device without the anti-reflection layer.
Finally, we completely discuss the photoelectronic characteristics and possible emission mechanisms of a WOLED configured with blue fluorescence and phosphorescent iridium complexes proposed as well. Evidence indicates that the good energy overlap between the absorption spectrum of Ir(ppy)3 and Ir(piq)2(acac) and the emission spectrum of TPBI results in an effective energy transfer from TPBI to Ir(ppy)3 and Ir(piq)2(acac). In addition, the WOLED with iridium complexes comprising a ZnSe film as a buffer layer and a dual electron transporting layer of CuPc/TiOPc as an anti-reflection layer has been fabricated. Evidenced shows that holes and electrons can be injected from the electrodes to the emission layer via ZnSe and CuPc/TiOPc layer, respectively, which enhances the electron-hole recombination. Additionally, contrast ratio is enhanced by a factor of 2 owing to the use of a CuPc/TiOPc anti-reflection layer.

致謝 (Acknowledgment) I
中文摘要 II
Abstract IV
Contents VI
Figure Captions IX
Table Captions XV
Chapter 1 Introduction 1
1-1 History of Organic Light Emitting Diodes 1
1-2 Motivation 5
1-3 Organization of This Thesis 6
Chapter 2 Basic Concepts and Experimental Procedure 8
2-1 Electroluminescence in Organic Materials 8
2-2 Charge Carrier Injection and Transporting 9
2-3 Effects of Doping 13
2-4 Emission Mechanisms of Organic Materials 14
2-5 Experimental Procedure 16
2-5-1 ITO Substrate Cleaning and patterning 16
2-5-2 Fabrication of Organic Light Emitting Diodes 18
2-5-3 Measurements and Tests 18
Chapter 3 An Investigation of the Hole Injection Properties of Organic Light-Emitting Diodes 20
3-1 Effect of Laser-Etched Indium Tin Oxide on Optoelectrical Properties of Organic Light-Emitting Diodes 20
3-1-1 Introduction 20
3-1-2 Experiments 21
3-1-3 Results and discussion 23
3-1-4 Summary 25
3-2 Effects of Light Scattering Layer on Outcoupling Efficiency in Organic Light Emitting Diodes 26
3-2-1 Introduction 26
3-2-2 Experimental 28
3-2-3 Results and Discussion 29
3-2-4 Summary 32
3-3 Enhanced Power Efficiency by insertion of semiconductor buffer layer in Organic Light Emitting Diodes 33
3-3-1 Introduction 33
3-3-2 Experiments 35
3-3-3 Results and discussion 36
3-3-4 Summary 38
Chapter 4 Enhancing the Contrast and Power Efficiency of Organic Light Emitting Diodes using CuPc/TiOPc as an Anti-reflection Layer 39
4-1 Introduction 39
4-2 Experimental details 41
4-3 Results and discussion 42
4-4 Summary 46
Chapter 5 High Efficiency White Organic Light-Emitting Diode with Iridium Complexes 47
5-1 Full-Wavelength White Organic Light-Emitting Diodes with Blue Fluorescence and Phosphorescent Iridium Complexes 47
5-1-1 Introduction 47
5-1-2 Experimental 49
5-1-3 Results and discussion 50
5-1-4 Summary 52
5-2 Enhancement on the Efficiency and Contrast of Phosphorescent White Organic Light-Emitting Diodes 53
5-2-1 Introduction 53
5-2-2 Experimental 54
5-2-3 Results and Discussion 55
5-2-4 Summary 57
Chapter 6 Conclusions and Future Work 58
6-1 Conclusions 58
6-2 Future Work 59
References 60
Publications 118
Patents 123
Biography 124

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