- 學位論文
以芴為主體之電洞傳輸層材料設計、合成與元件應用
Design, Synthesis and Application of Fluorene-Based Hole Transporting Materials
摘要
近年，有機發光二極體 (Organic Light Emitting Diodes，OLEDs)已有非常多的研究者投入開發，並致力於發光效率的提升。其中，激發錯合物 (exciplex) 更是有機發光二極體歷史中一項重要的沿革。激發錯合物的優勢在於它的電子予體 (donor) 與電子受體 (acceptor) 為兩個獨立的分子，可以有效降低前沿分子軌域間的重疊比例，使其三重態與單重態間的能隙 (∆EST) 縮小，以提高良好的反向系統間跨越速率 (reverse intersystem crossing，RISC)，進而增加整體元件的內部量子轉換效率。 在本篇論文中，我們設計並合成了一系列以芴 (fluorene) 為主體的電洞傳輸層材料 (hole-transporting materials, HTMs)，並與適當的電子傳輸層材料 (electron-transporting materials, ETMs) 搭配運用於激發錯合物上，利用激發錯合物系統希望能增加藍光元件的效率，並藉由光物理與元件性質分析，探討分子結構、特性與元件效能之間的關係。在第一章中，將簡單介紹有機發光二極體的發展、原理和芴的特性。在第二章中，我們將電洞傳輸層材料中常見的咔唑 (carbazole) 置換成咔啉 (carboline)。利用改變咔啉環上氮的位置，調控分子的性質，期望能使最高佔有分子軌域 (highest occupied molecular orbital，HOMO) 的能量下降，進而使激發錯合物放光藍移。另一方面，在第三章及第四章，我們將探討芴 (fluorene) 的2、7號位接上不同的取代基對於其結構特性的影響。在第三章中，所選擇之電子予體為9-苯基咔唑 (9-phenylcarbazole)，並與現有的電子予體性質進行比較，期望能進一步改善激發錯合物之效率。第四章則是以二苯並噻吩 (dibenzothiophene) 衍生物作為新的電子予體，期望能使最低佔有分子軌域 (lowest occupied molecular orbital，LUMO) 的能量下降，並探討二苯並噻吩之不同位置連接芴對形成激發錯合物的影響。第五章則是將二苯並噻吩之衍生物在芴上修飾氰基，並探討其熱激活化延遲螢光 (thermally deactivated delayed-fluorescence, TADF) 性質。
並列摘要
Nowadays, organic light-emitting diodes (OLEDs) are promising devices and many scientists have put a lot of effort into efficiency improvement. Historically, exciplex is one of the milestones of OLEDs. The advantages of exciplex include well-separated frontier orbitals, small energy gap between singlet and triplet excited state (ΔEST), and efficient reverse intersystem crossing (RISC). All advantages mentioned above lead to high internal quantum efficiency. In this thesis, a series of fluorene-based hole-transporting materials were designed, synthesized, and utilized in emitting layers of OLEDs with proper electron-transporting materials. In the 1st chapter, OLEDs and characteristics of fluorene were briefly introduced. In the 2nd chapter, carboline was introduced as electron-donating group instead of carbazole, which is a molecule commonly used in hole-transporting materials. By adjusting the position of nitrogen in carboline the energy level of highest occupied molecular orbital (HOMO) was controlled and the exciplex emission was expected to blueshift. On the other hand, in the 3rd and 4th chapter, different substituents were introduced onto fluorene core and a series of hole-transporting materials with different donors were synthesized and examined. In the 3rd chapter, 9-phenylcarbazole was introduced as donor group and the properties of resulting molecules were compared to fluorene/carbazole-based molecules. In the 4th chapter, new donors based on amine derivatives with dibenzothiophene were designed and synthesized. In addition, dibenzothiophene was linked with nitrogen on different position and the resulting properties were examined. For these three chapters we selected appropriate electron-transporting materials to arrange in pairs with the hole-transporting materials. The performance of exciplex and OLED device are shown and discussed in this thesis. Last, in the 5th chapter, we added cyano group on the fluorene skeleton of molecules in the 4th chapter. The molecules have thermally deactivated delayed-fluorescence (TADF) and the properties are studied in this chapter.
參考文獻
延伸閱讀
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