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標題: | 高效率熱激活延遲螢光之有機發光二極體材料與激態複合體之結構研究 Probe Exciplex Structure of Highly Efficient TADF OLEDs |
作者: | Tzu-Chieh Lin 林子傑 |
指導教授: | 周必泰(Pi-Tai Chou) |
關鍵字: | 激態複合體,步進式掃描,傅立葉轉換遠紅外光光譜儀,熱激活延遲螢光, Exciplex,step-scan,FT-IR,TADF, |
出版年 : | 2017 |
學位: | 博士 |
摘要: | 第一章
近年來含有硼烷基受體的熱激活延遲螢光(TADF)分子正引起學者們的注意,不過到現在還沒有人合成過在N供體和硼烷受體之間具有直接B-N連接的TADF放光分子。所以於合成上應簡化分子結構,從而促進合成設計和多功能性。此篇論文中我們合成了含有N-borylated和acridine(吖啶)受體的全新系列化合物:ACBM,PACBM和SACBM。進行光譜學分析可以發現到這些化合物具有顯著的溶劑化效應和TADF光物理性質。藉由時間依據的DFT計算化合物的HOMO和LUMO可以發現在空間中有明顯的分子內電荷轉移。而其中的SACBM樣品,可以製作出綠色發光的OLED元件,其CIE色度和最大外量子放光效率為(0.22,0.59),而元件的發光效率、功率及效率分別為19.1%,60.9cd / A和43.6lm / W,是一個具有極高效率並含有N-borylated 的OLED發光材料。 第二章 此篇論文我們研究將咔唑 (carbazole) 作為主要結構的電子提供者CN-Cz2及1,3,5-三嗪 (triazine) 作為基礎的電子接受者 (PO-T2T) 共同蒸鍍形成分子間電荷傳遞 (intermolecular charge transfer) ,熱激活延遲螢光 (TADF) 且放光效率極高的有機發光二極體材料之固體薄膜,其外部量子效率 (EQE) 可達16%。利用pump-probe步進式掃描 (step-scan) 傅立葉轉換紅外光譜儀來偵測其所形成的激態複合體 (exciplex) ,並從激發態的紅外光譜來明顯區分CN-Cz2及PO-T2T的區域性激發態 (LE) 或者是電荷轉移態 (CT) ,其中最為重要的是我們在CN-Cz2:PO-T2T的瞬時紅外吸收圖譜發現到一個寬大且中心大概位於2060 cm-1的吸收譜帶,其名為polaron吸收譜帶。透過仔細的時間解析可以了解到激態複合體的電荷轉移態會透過延遲放射螢光的過程經過大約3 µs緩解至中間基態緊接著再由結構緩解回到最原始的區域性基態,結構緩解的時間尺度大約14 µs。 偵測固態樣品的光學性質一直是一個困難的挑戰,藉由pump-probe步進式掃描 (step-scan) 傅立葉轉換紅外光譜儀可以提升相當多的光學靈敏度及提供激發態相當詳細的分子震動變化訊息,此篇論文主要是偵測激態複合體分子間的電荷轉移及相互作用,還有相當多的高效率分子內有機發光二極體材料可以研究,此外還能架設循環式液體系統,透過幫浦以一定的流速來更新樣品同樣也可以偵測液體樣品,使的此技術可以發展得更加多元。 Chapter 1 Despite the fast boom of thermally activated delayed fluorescence (TADF) emitters bearing borane-based acceptor, so far, no TADF emitter with a direct B−N linkage between N-donor and boryl acceptor has been reported. The latter should simplify the molecular architecture and hence facilitate the synthetic design and versatility. We report here the preparation and characterization of a new series of N-borylated compounds with functional acridine donor unit; namely: ACBM, PACBM, and SACBM. Spectroscopic studies were performed to explore their photophysical properties that exhibited prominent solvatochromism and thermally activated delayed fluorescence. The time-dependent DFT calculation indicated the involvement of substantial intramolecular charge transfer character for which HOMO and LUMO are spatially separated. For compound SACBM, fabrication of green emitting OLED gave CIE chromaticity of (0.22, 0.59) and maximum external quantum efficiency, luminance efficiency and power efficiency of 19.1%, 60.9 cd/A, and 43.6 lm/W, respectively, demonstrating for the first time the highly efficient OLEDs using N-borylated TADF emitters. Chapter 2 We report here for the first time the pump-probe step-scan Fourier transform IR spectra of exciplex composed of a new carbazole-based electron donor (D: CN-Cz2) and 1,3,5-triazine-based electron acceptor (A: PO-T2T) co-deposited on the solid film that gives rise to highly efficient intermolecular charge transfer (CT), thermally activated delayed fluorescence (TADF), and record-high exciplex type OLEDs (EQE: 16%). The IR spectral assignment to the CT state is unambiguous due to its distinction from the local excited (LE) state of either the donor or the acceptor chromophore. More importantly, a continuous, broad absorption band centered at ~2,060 cm-1 was observed in the CN-Cz2:PO-T2T transient IR spectrum and assigned to a polaron absorption. Comprehensive time-resolved kinetics lead us to conclude that CT excited states relax to a ground-state intermediate with a time constant of ~3 µs, followed by a structural relaxation to the original prepared CN-Cz2:PO-T2T LE configuration within ~14 µs. The detection of the optical properties of solid samples has been a difficult challenge. Pump-probe step-scan FT-IR cna increase the amount of optical sensitivity and provide a very detailed molecular vibration message in excited state. Here, we tried to detect exciplex and the charge transfer and interaction between donor and acceptor. In addition to that, using this technic, there are a lots of high efficiency intra-molecular OLED materials can be studied. Except to solid sample, we can setup a circulating liquid system, through the peristaltic pump to provide the a certain flow rate to renew sample solution can also detect liquid samples, making this instrument can be developed more diverse. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/68038 |
DOI: | 10.6342/NTU201800022 |
全文授權: | 有償授權 |
顯示於系所單位: | 化學系 |
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