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研究生： 周郭憲
Chou, Kuo-Hsien
論文名稱： 七元環電子傳輸材料製作高效率有機發光二極體
Highly Efficient OLEDs with Seven-Member-Ring Based Electron Transporting Materials
指導教授： 周卓煇
Jou, Jwo-Huei
口試委員: 陳建添
Chen, Chien-Tien
王欽戊
Wang, Ching-Wu
岑尚仁
Chen, Sun-Zen
學位類別： 碩士
Master
系所名稱： 工學院 - 材料科學工程學系
Materials Science and Engineering
論文出版年： 2022
畢業學年度： 110
語文別： 中文
論文頁數： 79
中文關鍵詞： 有機發光二極體 、電子傳輸材料 、七元環
外文關鍵詞： OLED, Electron Transporting Materials, Seven-Member-Ring
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    • 有機發光二極體(Organic light-emitting diode, OLED)顯示器擁有高對比、自發光和廣視角等優勢，已在市場上取得巨大的成功；而OLED 照明擁有面光源、光線柔和、無眩光等特性，是極具潛力的照明技術；為了進一步提升 OLED 的競爭力，使其更節能省電，高效率OLED 的研發十分關鍵。
    達到高效率 OLED 的方法有：新材料研發、元件結構設計以及光取出結構設計等；在 OLED 元件裡，相比於電洞，電子的注入較少，使電子在發光層中的數目少於電洞，導致載子不平衡，進而降低元件效率，因此尋找良好的電子傳輸材料，改善電子的注入與傳輸，為提升 OLED 效率的關鍵。
    本研究使用四種新穎七元環電子傳輸材料，1-aza-DBdippy (DPP)、1-aza-DBdipPhCN (DPC)、1-aza-DBpPhCN (PC)與 1-aza-DBppy (PP)；透過乾式製程，探討對不同光色元件效率的影響；在綠光元件中，以DPP 製成的元件表現最優異，在亮度 1,000 cd/m2 時，相較於常見之TPBi，能量效率從 22.5 提升至 31.9 lm/W，增幅為 42%；電流效率從31.5提升至39.2 cd/A，增幅為24%；外部量子效率從8.7提升至10.9%，增幅為 25%；此提升歸結於 DPP 擁有：(1)良好的電子遷移率 (1.1×10-4cm2/ Vs)，使電子能更有效的注入發光層；(2)較深的 HOMO (6.3eV)，能有效阻擋電洞的流失，增加載子結合的機會。
    在藍光元件中，主體為 CBP 時，七元環材料的元件表現均低於TPBi 的元件；PC 效率的下降可歸因於高的 LUMO(2.32 eV)，不利電子的注入；PP 效率的下降歸結於 PP 擁有：(1)淺的 HOMO (6.01 eV)，無法將電洞限制於發光層內；(2)高的LUMO(2.11 eV)，提升電子注入的難度；(3)低的電子遷移率(1.3×10-6cm2/ Vs)，降低電子傳輸的效率；DPC 與 DPP 效率的下降則歸因於低的三重態能階，無法將激子限制於發光層；另外，主體使用 mCBP 時，PC 製成的元件擁有最佳的表現，亮度 100 cd/m2下，與使用 TPBi 的元件相比，能量效率從 13.1 上升至 18.7 lm/W，增幅為 43%；電流效率從 16.2 上升至 24.5 cd/A，增幅為 51%；外部量子效率，從 7.3 提升至 10.9 %，增幅為 49%；PC元件效率的提升歸結於它與發光層之間擁有電子陷阱，有益於電子注入發光層。

    Organic light-emitting diode (OLED) display has advantages of self-lit, wide viewing angle and high contrast, and has achieved a significant success in display market. Besides, OLED lighting has the characteristics of surface light source, soft diffused light and glare-free, becoming a lighting technology with great potential. In order to make OLED more competitive and more energy saving, the development of high-efficiency OLED is critical.
    Synthesis of new materials, design of efficiency-effective device architectures and light extraction structures are effective approaches to achieve high-efficiency OLED. Typically, electron is the minor carrier in OLED devices, causing carrier imbalance and low-efficiency. Therefore, the development of electron transporting material (ETM) is crucial for high-efficiency OLEDs.
    In this study, four novel ETMs, 1-aza-DBdippy (DPP), 1-aza-DBdipPhCN (DPC), 1-aza-DBpPhCN (PC), and 1-aza-DBppy (PP), were used. Through dry process, the effect of ETMs on the green and blue device was discussed. Among green devices, the device made of DPP performed the best. For example, at 1,000cd/m2, compared with TPBi based device, the power efficacy (PE) improved from 22.5 to 31.9lm/W, an improvement of 42%, the current efficacy (CE) increased from 31.5 to 39.2cd/A, an improvement of 24% and external quantum efficiency (EQE) improved from 8.7 to 10.9%, an increment of 25%. The improvement may be attributed to the fact that DPP has (1) faster electron mobility enables electrons injecting into emissive layer more efficiently, (2) deeper HOMO enables a better hole blocking ability, increasing the recombination with electrons.
    Among the CBP-host composing blue light devices, the device performance of all seven-member ring material is lower than that of TPBi. The device efficiency decrement of PC can be attributed to high LUMO of PC (2.32eV), reducing the injection of electron. The device efficiency decrement of PP is due to the fact that DPP has shallow HOMO (6.01eV), high LUMO (2.11eV) and low electron mobility. The weak performance of DPC and DPP may be due to low triplet energy level, resulting in inefficient exciton confinement. As mCBP was used in lieu of the CBP, the blue device composing PC performed the best. For example, at 100 cd/m2, PE improved from 13.1 to 18.7lm/W, an improvement of 43%, CE improved from 16.2 to 24.5cd/A, an improvement of 51% and EQE improved from 7.3 to 10.9%, an improvement of 49%. These can be attributed to device structure showing an electron-trapping rather than a barrier, which facilitates the injection of electrons.

    摘要..............I Abstract..............III 致謝..............V 目錄..............IX 表目錄..............XI 圖目錄..............XI 壹、緒論..............1 貳、文獻回顧..............3 2-1、OLED 的發光原理..............3 2-2、OLED 的能量轉移機制..............5 2-3、OLED 材料之發展..............7 2-3-1、陽極材料..............7 2-3-2、電洞注入材料..............8 2-3-3、電洞傳輸材料..............8 2-3-4、發光層材料..............9 2-3-5、電子傳輸材料..............13 2-3-6、電子注入材料..............14 2-3-7、陰極材料..............14 2-4、OLED 元件效率..............15 2-5、高效率 OLED 的製作技術..............16 2-6、光色定義..............20 2-7、電子傳輸材料之種類..............21 2-7-1、噁二唑(Oxadiazole)衍生物 ..............21 2-7-2、唑類化合物(azole-based materials) ..............23 2-7-3、金屬螯合物(Metal chelates) ..............26 2-7-4、含矽之雜環類化合物 ..............28 2-7-5、其他類型..............29 2-8、三重態激子侷限..............34 參、實驗方法..............35 3-1、本研究所選用之材料..............35 3-1-1、材料之功能、全名及簡稱 ..............35 3-1-2、材料之化學結構..............37 3-2、元件設計與製備..............41 3-2-1、基板電路設計..............41 3-2-2、基板清洗..............41 3-2-3、真空蒸鍍裝置..............42 3-2-4、鍍膜速率測定..............43 3-3、元件光電特性量測..............44 3-3-1、元件電流、電壓與亮度特性之量測 ..............44 3-3-2、發光效率之計算..............46 肆、結果與討論..............47 4-1、電子傳輸材料的物理特性..............47 4-2、元件結構..............55 4-2-1、綠光元件結構..............55 4-2-2、藍光元件結構..............56 4-3、電子傳輸材料對綠光、藍光元件之影響..............58 4-3-1、綠光元件的探討..............58 4-3-2、藍光元件的探討..............62 伍、結論..............70 陸、參考文獻..............72 附錄、個人著作目錄 ..............79 (A) 期刊論文..............79 (B) 研討會論文..............79 (C) 獲獎紀錄..............79

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