||Investigation and Fabrication of Metal Oxide Hole Injection Layer in Quantum Dot Light Emitting Diode
||Institute of Microelectronics
quantum dot light emitting diodes
第一個部分通過氧化鎳前驅物溶液濃度的調變控制元件性質，元件發光層為硒化鎘/硫化鋅核殼型量子點以及電子傳輸層為氧化鋅奈米粒子，分別獨立塗佈於氧化銦錫透明基板，製造出氧化鎳全無機量子點發光二極體。適當的濃度(2M)使得元件具有較高的厚度以及更低的表面粗糙度。最高亮度3071 cd/m^2，電流效率0.3 cd/A。
第二部分使用醋酸銅摻雜到氧化鎳前驅物內作為電洞注入層，製成全無機量子點發光二極體。實驗結果發現當Cu:Ni摻雜濃度由0.5%→1.5%時，亮度可以從3155 cd/m^2到10892 cd/m^2，最大電流效率亦可從0.867 cd/A到0.965 cd。表示於低電壓操作環境不形成短路通道的前提下，適度的摻雜能有效提升元件效率。
而本文的第三部分中，驗證了第二部份製備的高性能元件擁有較高的氧化銅成分導致電洞傳輸層粗糙度的變化。證實混合材料可將高電洞遷移率的氧化銅與氧化鎳結合，進而改善載子平衡。並成功使用醋酸銅製備氧化銅前驅物，取代氧化鎳為電洞傳輸層。實驗結果顯示以氧化銅作為電洞傳輸層的元件與沒有摻雜的氧化鎳元件相較，擁有更小的驅動電壓，最高亮度17030 cd/m^2以及最大電流效率1.67 cd/A。
Quantum dots are a good contender for the next generation of luminescent materials because of their excellent luminescent properties. In this paper, three kinds of colloids are developed and metal oxide is formed by spin coating method as the hole transport layer film. To construct an all-inorganic red light quantum dot light-emitting diode with exceptional brightness and color purity. This thesis is divided into three parts.
The first part controls the properties of the device by adjusting the concentration of the nickel oxide precursor solution. The device light emitting layer is a cadmium selenide/zinc sulfide core-shell type quantum dot and the electron transport layer is a zinc oxide nanoparticle independently coated on indium tin oxide transparent substrate, to produce a nickel oxide fully inorganic quantum dot light-emitting diode. The appropriate concentration (2M) allows the device to have a higher thickness and lower surface roughness, a maximum brightness of 3071 cd/m^2, and a current efficiency of 0.3 cd /A.
The second part uses copper acetate doped into the nickel oxide precursor as a hole injection layer to make a fully inorganic quantum dot light-emitting diode. The experimental results show that when the doping concentration of Cu:Ni is from 0.5% to 1.5%, The brightness is from 3155 cd/m^2 to 10892 cd/m^2. The maximum current efficiency is also from 0.867 cd/A to the last 0.965 cd. The results show that under the premise that the low voltage operation environment does not form a short circuit channel, moderate doping can effectively improve the device efficiency.
In the third part of thesis, it is verified that the high-performance components prepared in the second part of the paper have a higher copper oxide composition and cause the change in the roughness of the hole transport layer. It was confirmed that the mixed material can combine copper oxide and nickel oxide with high hole mobility to improve carrier balance. The successful use of copper acetate to prepare copper oxide precursor, replacing nickel oxide as a hole transport layer. The experimental results show that the device using copper oxide as a hole transport layer has a smaller driving voltage, a maximum brightness of 17030 cd/m^2, and a maximum current efficiency of 1.67 cd/A compared with the undoped nickel oxide element.
Table Captions VIII
Figure Captions IX
Chapter 1 Introduction 1
1.1 Introduction of electrical operating QD-LEDs 1
(I) Tunable and bright colours : 1
(II) Bright emission : 1
1.2 Four categories of QD-LEDs 3
Type I : polymer CTLs 3
Type II : Organic small molecule CTLs 3
Type III: Inorganic CTLs 3
Type IV : Hybrid organic-inorganic CTLs 4
1.3 Metal oxide semiconductor 4
1.4 Hole injection layer by Sol-gel method 5
1.5 Motivation 7
Chapter 2 Experiment process and measurement 12
2.1 Materials in the experiment 12
2.1.1 Sol-Gel hole transport layer 12
2.1.2 Emission material 12
2.1.3 Electron transporting layer 13
2.2 Experiment Process 13
2.3 Measurement method 14
Chapter 3 QD-LEDs based on NiOx 18
3.1 Thickness of NiOx HIL/HTL in all-organic QD-LEDs 18
3.1.1 Literature Review 18
3.1.2 Device Fabrication 18
3.1.3 Result and Discussion 19
3.1.4 Summary 20
3.2 Copper Doping of NiOx HTL in all-inorganic QD-LEDs 29
3.2.1 Literature Review 29
3.2.2 Device Fabrication 30
3.2.3 Result and Discussion 31
3.2.4 Summary 31
Chapter 4 QD-LEDs based on CuO 38
4.1 Literature review 38
4.2 Device fabrication 38
4.3 Result and Discussion 39
4.4 Summary 40
Chapter 5 Conclusion and Future Prospect 50
5.1 Conclusion 50
5.2 Future Prospect 51
5.2.1 Optimize thickness of NiOx HTL 51
5.2.2 Simplify the process 51
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