高效率有機發光二極體的新穎雙極性主體材料及光萃取之研究

Investigation of Novel Bipolar Host Materials and Light Out-Coupling for Highly Efficient Organic Light-Emitting Diodes

林銘祥(Ming-Shiang Lin)

指導教授 ： 吳忠幟

國立臺灣大學/電機資訊學院/光電工程學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.10248

摘要

在本論文中，我們探討了高效率磷光有機發光二極體的兩種新穎雙極性主體材料及光萃取技術。首先我們討論兩種高三重態能量雙極性主體材料，CMesB和mCPCN。
CMesB被設計成同時具有電洞和電子傳輸的能力，其中包含兩個三甲基硼烷及一個咔唑分子。所有基於CMesB的紅/綠/藍/白光磷光有機發光二極體，都在實用亮度範圍內展現出良好的外部量子效率（紅：20.7 %，綠：20.0 %，藍：16.5 %，白：15.7 %）。這樣的結果顯示，具有高三重態能量的雙極性主體材料CMesB，在製造顯示及照明用途的紅/綠/藍/白光磷光有機發光二極體上，有相當高的潛力。
接著，我們介紹另一個具有高三重態能量的不對稱雙極性磷光主體材料mCPCN，是將氰基加到mCP分子所構成。包含mCPCN的單載子元件特性，說明了它擁有相對平衡的電洞�電子注入及傳輸性質。最大外部量子效率達26.4 %，電流效率達58.6 cd A-1，以及功率效率達到 57.6 lm W-1的高效率藍光磷光有機發光二極體已被實現。使用mCPCN的藍光磷光有機發光二極體呈現相當低的高亮度效率衰減，並在每平方公尺一千燭光及八千燭光的亮度下，仍分別保持約25 %及20 %的外部量子效率。此外，mCPCN也成功地應用在白光磷光有機發光二極體上，獲得超過23 %的外部量子效率。
最後，我們針對氧化銦錫陽極厚度對有機發光二極體光萃取效率的影響進行了理論計算及實驗驗證。製作在不同氧化銦錫厚度上的綠光雙發光層磷光有機發光二極體，各項效率特性表現出顯著的差異（外部量子效率：1.21倍，電流效率：1.30倍，功率效率：1.23倍），與理論計算的結果相當一致。

關鍵字

磷光有機發光二極體 ； 雙極性主體材料 ； 藍光磷光有機發光二極體 ； 白光磷光有機發光二極體 ； 光萃取效率

並列摘要

In this dissertation, we investigate two novel bipolar host materials and a light out-coupling technique for highly efficient phosphorescent organic light-emitting diodes (PhOLEDs). First we discuss the concepts of bipolar host materials with high triplet energy, and then introduce two host materials, CMesB and mCPCN.
CMesB contains the dimesityl borane/carbazole hybrid and is designed to have both hole- and electron-transporting capabilities. Red/green/blue/white PhOLEDs based on CMesB all showed high external quantum efficiencies (20.7 % for red, 20.0 % for green, 16.5 % for blue, and 15.7 % for white) at practical brightnesses. The results indicate that bipolar host CMesB with the high triplet energy has high potential in manufacturing RGBW PhOLEDs for display or lighting applications.
Next, we report another novel asymmetric bipolar and high-triplet-energy phosphorescent host material, mCPCN that incorporates one cyano group onto mCP. Characteristics of single-carrier devices containing mCPCN indicate its rather balanced hole/electron injection and transport properties. Highly efficient blue PhOLEDs with maximum external quantum, current and power efficiencies of 26.4 %, 58.6 cd A-1, and 57.6 lm W-1, respectively, were achieved. Blue PhOLEDs adopting mCPCN exhibited impressively low efficiency roll-off up to the brightness of 10000 cd m-2, retaining a high quantum efficiencies of ~ 25 % at 1000 cd m-2 and ~ 20 % even at 8000 cd m-2. mCPCN had also been successfully used in implementing highly efficient white PhOLEDs having external quantum efficiencies in excess of 23 %.
Finally, we investigated the influence of ITO anode thickness on light out-coupling efficiency of OLEDs theoretically and experimentally. The efficiency characteristics of green D-EML PhOLEDs with different ITO thicknesses showed remarkable variations (1.21 times in quantum efficiencies, 1.30 times in cd A-1 efficiencies and 1.23 times in lm W-1 efficiencies), and agreed with the simulated results.

並列關鍵字

phosphorescent OLEDs ； bipolar host materials ； blue PhOLEDs ； white PhOLEDs ； light out-coupling efficiency

參考文獻

CH1

[1] M. A. Baldo, D. F. O’Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompson, and S. R. Forrest, Highly efficient phosphorescent emission from organic electroluminescent devices, Nature, 1998, 395, 151-154.

[2] Y. Kawamura, K. Goushi, J. Brooks, J.J. Brown, H. Sasabe and C. Adachi, 100% phosphorescence quantum efficiency of Ir(III) complexes in organic semiconductor films, Appl. Phys. Lett., 2005, 86, 071104.

[3] Y. L. Tung, S. W. Lee, Y. Chi, Y. T. Tao, C. H. Chien, Y. M. Cheng, P. T. Chou, S. M. Peng and C. S. Liu, Organic light-emitting diodes based on charge-neutral Os(II) emitters: generation of saturated red emission with very high external quantum efficiency, J. Mater. Chem., 2005, 15, 460-464.

[4] D. Tanaka, H. Sasabe, Y. J. Li, S. J. Su, T. Takeda and J. Kido, Ultra High Efficiency Green Organic Light-Emitting Devices, Jpn. J. Appl. Phys., 2007, 46, L10-L12.