有機發光二極體光萃取研究，具高玻璃轉換溫度主體材料之磷光有機發光二極體與強共振腔有機發光二極體之壽命延長

Study on light extraction enhancement of organic light emitting diode (OLED), phosphorescent OLED with high-Tg hosts, and lifetime elongation of strong-cavity OLED

林聖傑(Sheng-Chieh Lin)

指導教授 ： 李君浩

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202002669

摘要

本論文有三個部分，第一部分介紹以咔唑(carbazole)與苯並咪唑(benzimidazole)衍生物為主體材料製作高效率藍色磷光與長壽命綠色磷光有機發光二極體，第二部分為高效率綠色磷光有機發光二極體之光萃取研究，第三部分為具有強共振腔效應之有機發光二極體壽命延長。
在第一部分我們使用台大化學所梁文傑教授實驗室所提供的三種具有咔唑與苯並咪唑之衍生物作為主體材料製作高效率藍色磷光與長壽命綠色磷光有機發光二極體。藉由增加咔唑的數量使得所有化合物的玻璃轉化溫度(Tg)皆在180 ℃以上。在這三種化合物中，9-(1,2-diphenyl-1H-benzo[d]imidazol-4-yl)-9H-3,6-di(N-carbazolyl)carbazole (4-3cbzBIZ)摻雜bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic)之藍色磷光有機發光二極體其最高電流效率、功率效率和外部量子效率分別為58.73 cd/A、59.31 lm/W和28.58%。而在4-3cbzBIZ中摻雜tris[2-phenylpyridinato-C2,N]iridium(III) (Ir(ppy)3)之綠色磷光有機發光二極體在初始亮度為30,000 cd/m2下的壽命為使用4,4’-Bis(N-carbazolyl)-1,1’-biphenyl (CBP)作為主體材料之3.03倍。
第二部分我們使用東華大學魏茂國教授實驗室所提供的三種不同週期之光柵(833.33, 416.67, 277.78 奈米)來製作綠色磷光有機發光二極體，藉由調控陽極及元件電洞傳輸層之厚度優化並搭配週期為416.67奈米的光柵作為內部結構且利用半球透鏡作為外部結構製作元件，最高可得52.59%的外部量子效率以及106%的外部量子效率增益，且利用偏振片量測並進行波導模態與表面電漿模態的光萃取分析。
第三部分我們以薄鋁金屬作為陽極製作有機發光二極體，並且比較了1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile (HAT-CN)與氧化鉬(MoOx)兩種不同的電洞注入層，其中以氧化鉬作為電洞傳輸層之有機發光二極體有較低的阻抗及較高的穩定性，此外我們比較了以薄鋁和氧化銦錫做為陽極之有機發光二極體元件表現。利用薄鋁作為陽極搭配氧化鉬作為電洞傳輸層之有機發光二極體在調控電子傳輸厚度優化後，在定電流密度下操作壽命為使用氧化銦錫為陽極之有機發光二極體的2.92倍。

關鍵字

有機發光二極體 ； 咔唑 ； 玻璃轉化溫度 ； 奈米結構 ； 光萃取 ； 強共振腔

並列摘要

There are three topics in this thesis. First, we studied high-efficiency blue and long-lifetime green phosphorescent organic light-emitting diodes (PhOLEDs) by using carbazole and benzimidazole derivatives as host materials. Secondly, we studied light extraction through non-planar structures in high-efficiency green PhOLED. Lastly, we demonstrated the lifetime elongation of strong-cavity OLEDs.
In chapter 3, we used three benzimidazole derivatives with high glass transition temperature (Tg) over than 180 ℃, which were supplied by Prof. Man-Kit Leung’s group in Chemistry Department, National Taiwan University, as host materials for high-efficiency blue and long-lifetime green PhOLEDs. Among the three compounds, OLED with 9-(1,2-diphenyl-1H-benzo[d]imidazol-4-yl)-9H-3,6-di(N-carbazolyl)carbazole (4-3cbzBIZ) doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) achieved highest efficiency as 58.73 cd/A, 59.31 lm/W and 28.58% in current efficiency, power efficiency and EQE, respectively. Besides, operation lifetime of green PhOLED with 4-3cbzBIZ doped with tris[2-phenylpyridinato-C2,N]iridium(III) (Ir(ppy)3) had 3.03-times enhancement compared to that with 4,4’-Bis(N-carbazolyl)-1,1’-biphenyl (CBP) one.
In chapter 4, we studied the light extraction of green PhOLEDs with nanostructures (pitch = 833.33, 416.67, and 277.78 nm), which were supplied by Prof. Mao-Kuo Wei’s group, between the glass substrate and indium-zinc-oxide (IZO) anode. After optimizing thickness of IZO and hole-transport layer (HTL), green PhOLED with nanostructure and macrolens could achieve EQE value of 52.59% and enhancement ratio of 106%. Besides, we divided electroluminescence spectra into TE and TM mode to analyze light extraction mechanism.
In chapter 5, we used Al as the anode and compared device performances with molybdenum oxide (MoOx) and 1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile (HAT-CN) as the hole-injection layer (HIL) materials. Device with MoOx as HIL resulted in lower impedance and better stability. Besides, we compared device anode with Al and indium tin oxide (ITO). After optimizing thickness of electron-transport layer (ETL), operation lifetime of device with Al/MoOx as the anode/HIL had 2.92-times enhancement than device with ITO anode.

並列關鍵字

organic light-emitting diode ； carbazole ； glass transition temperature ； nanostructure ； light extraction ； strong-cavity

參考文獻

1. Rothberg, L. J.; Lovinger, A. J. Journal of Materials Research 2011, 11, (12), 3174- 3187.

2. Tang, C. W.; VanSlyke, S. A.; Chen, C. H. Journal of Applied Physics 1989, 65, (9), 3610-3616.

3. O’Brien, D. F.; Baldo, M. A.; Thompson, M. E.; Forrest, S. R. Applied Physics Letters 1999, 74, (3), 442-444.

4. Im, Y.; Byun, S. Y.; Kim, J. H.; Lee, D. R.; Oh, C. S.; Yook, K. S.; Lee, J. Y. Advanced Functional Materials 2017, 27, (13).

5. Lee, J.-H.; Chen, C.-H.; Lee, P.-H.; Lin, H.-Y.; Leung, M.-k.; Chiu, T.-L.; Lin, C.-F. Journal of Materials Chemistry C 2019, 7, (20), 5874-5888.