本研究選用聚乙二醇，將其添加至負型[6,6]-phenyl C61-butyric acid methyl ester (PCBM) 有機薄膜電晶體之主動層中，研究其對元件特性之影響。由實驗結果可知添加適當比例之高分子量聚乙二醇能夠有效的提高元件效能並且表現出較好的穩定性。在本研究中，加入聚乙二醇之元件載子遷移率可由0.014 cm2/Vs 提升至0.044 cm2/Vs，而臨界電壓也可由17V縮小至-2V。在大氣環境下量測，未添加聚乙二醇之元件載子遷移率變為原本之千分之一，而添加聚乙二醇後則為十分之一。這可歸功於聚乙二醇分子與鋁電極產生化學反應，進而減少電子注入障礙。

This study investigates the effect of blending of poly(ethylene glycol) (PEG) into the active layer on the performance of n-channel organic thin-film transistors (OTFTs) based on [6,6]-phenyl C61-butyric acid methyl ester (PCBM). We found that the performance and the stability of the OTFTs could be enhanced after the addition of PEG. The mobility could be improved from 0.014 to 0.044 cm2/Vs, and the threshold voltage shifted from 17V toward to -2V. In the ambient conditions, the mobility of the pristine-PCBM device degraded by three orders. However, the one of the device prepared with PEG only decreased by one order. The enhancement could be attributed into the reduction of the electron injection barrier due to the chemical reactions between PEG molecules and Al atoms of the source/drain electrodes.

中文摘要 i
Abstract ii
謝誌 iii
Contents iv
List of Figures vi
List of Tables viii

Chapter 1 1
Introduction 1
1.1 Preface 1
1.2 Organic Thin-Film Transistors 3
1.2.1 Introduction to Organic Semiconductors 3
1.2.2 Overview of Organic Thin-Film Transistors 3
1.2.3 Overview of n-channel Organic Thin-Film Transistors 4
1.2.4 Introduction to the N-channel Material PCBM 6
1.3 Motivation 7
1.4 Thesis Organization 9
Chapter 2 10
Mechanism and Operation 10
2.1 Structures of Organic Thin Film Transistors 10
2.2 The Charge Carrier Transportation in Organic Semiconductors 11
2.2.1 Preface 11
2.2.2 Polaron and Bipolaron 12
2.2.3 Hopping Model 13
2.2.4 Multiple Trapping and Release Model (MTR) 14
2.3 The Operation of Organic Thin-Film Transistors 14
2.3.1 Energy Level Principle and Carrier Distribution 14
2.3.2 The Methods of Extracting Parameters 18
2.3.3 Contact resistance 20


Chapter 3 21
Experimental and Analysis Methods 21
3.1 Substrate Preparation 21
3.1.1 Preface 21
3.1.2 ITO Patterning Process 21
3.1.3 Cleaning of ITO/Glass Substrate 23
3.1.4 Cleaning of SiO2/Si Substrate 23
3.2 The Materials 24
3.3 Device Fabrication Process of OTFTs 25
3.3.1 Spin-Coating Polymer Dielectric Film 25
3.3.2 Spin-Coating of PCBM/PEG Blends as the Active Layer and Evaporation of Metal Electrodes 25
3.4 Measurements and Analysis of OTFTs 28
3.4.1 Electrical Characteristics 28
3.4.2 Capacitance Analysis 28
3.4.3 Surface Morphology Measurement 28
3.4.4 X-ray Photoelectron Spectroscopy Measurement 30
Chapter 4 32
Results and Discussion 32
4.1 Characteristics of Device Electrical Properties 32
4.1.1 The Effect of Molecular Weight of PEG 32
4.1.2 The Effect of PEG Concentration 35
4.1.3 The Electrical Characteristics Measured in the Atmosphere 38
4.1.4 The Effect of PEG on the Devices Fabricated on PVP/SiO2 Substrate 40
4.2 Morphological Analysis of the Active Films 43
4.3 Analysis of Device Resistances 45
4.4 The Analysis of XPS Measurements 48
Chapter 5 49
Conclusion and Future Work 49
5.1 Conclusion 49
5.2 Future Work 49
Reference 50

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