具分子內與分子間電荷轉移行為之材料的設計、合成、鑑定與其在有機發光二極體上之應用

Abstract

有機光電元件相較於傳統的無機光電元件，具有低成本、製程難度較低、可撓性等優勢，受到學界及業界的高度重視。具有低單重態及三重態能階差的有機材料，因其具有使用100%激子的潛力，近年來成為第三代有機發光二極體 (OLEDs) 的主流。近年來，主要有兩種方法設計具此一性質的有機材料：熱激活化延遲螢光 (thermally activated delayed fluorescence, TADF) 及激發錯合體 (Exciplex)。兩種皆利用分離分子中最高佔據分子軌域 (HOMO) 與最低未佔分子軌域 (LUMO) 來降低單重態及三重態能階差。藉由適當的分子設計與合宜的元件材層，可使整體元件外部效率超過30%，因此成為近期OLED研究領域中的熱門題目。 在本論文中，主要設計與合成一系列以咔唑為核心的有機光電材料，並應用於第三代OLED (TADF OLEDs) 的發光層中作為主體或客體材料，相關的材料性質將一併在本文中分析與討論。各章節內容簡要如下：第一章介紹OLEDs之相關背景知識；第二章以先前發表的分子 (CzT) 做延伸，藉由置換電子予體 (donor) 或改變其拓樸結構，探討對TADF性質和元件表現的影響；第三章以9-苯基咔唑 (CzP) 為核心，藉由改變核心上donor數量與強度、或將donor接在CzP的1號位，又或是引入異核原子於兩核心間，藉此探究對分子特性與元件表現的影響。

Organic optoelectronic devices have attracted intense attention from researchers and companies all over the world for their low cost, ease of production, and mechanical flexibility compared to traditional inorganic optoelectronic devices. The molecules with small singlet and triplet energy gap (ΔEST) are the mainstream of current OLEDs development due to their potential of utilizing 100% excitons. Nowadays, there are two main routes to design small ΔEST organic materials, thermal activated delayed fluorescence (TADF) and exciplex. Both strategies are in an aim to separate distribution of HOMO and LUMO in order to further reduce ΔEST. The external quantum efficiency can be surpassed 30% by utilizing adequate molecules with proper device’s fabrication. Therefore, it has been attractive to both academia and industry. In this thesis, a series of carbazole-based organic optoelectronic materials utilized in TADF OLEDs as either host or guest materials were designed, synthesized, and characterized. The essence of each chapters are briefly introduced as follows. 1st chapter provides an overview for OLEDs and 2nd chapter extends the previously published molecule (CzT) to investigate the effects on TADF properties and device performance through introducing different electron donors and then changing their topology. In chapter 3, we take 9-phenylcarbazole (CzP) as the core of HTMs. We investigate the effects on molecule properties and device performance by manipulating the strength of donors, connecting the donor to the 1st position of CzP, or introducing hetero-atoms between two CzPs.