以苯并噻二唑及喹喔啉衍生物為主體之有機功能性材料的設計、合成與性質

Design, Synthesis and Characteristic of 2,1,3-Benzothiadiazole Derivative and Quinoxaline Derivative-Based Organic Functional Materials

張宇翔(Yu-Hsiang Chang)

指導教授 ： 汪根欉

國立臺灣大學/理學院/化學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003269

摘要

相較於傳統之無機材料，有機功能性材料具有生產成本較低、可製成可撓曲元件等優點，並可以透過分子設計改變其吸光及放光之行為，因此近年來有關的研究相當盛行。在有機功能性材料的領域中，有機太陽能電池、有機發光二極體以及具有雙光子吸收性質之材料是三種相當熱門的研究主題。有機太陽能電池是利用具有高吸光係數及高載體遷移率之有機分子作為元件之主動層，吸收光能以轉換為電能，在能源逐漸耗竭的現今更加受到矚目；有機發光二極體則是以具有高螢光或磷光量子產率之有機分子作為元件之發光層，將電能轉換為光能，目前也已經廣泛的應用於商業製程中；另外，具有雙光子吸收性質之有機分子可以於皮下組織吸收近紅外光以進行光動力療法或是生物顯影，於生醫領域亦有顯著的應用。

在本篇論文中，第一章為有機功能性材料的簡介，我們將回顧有機功能性材料之發展，以及如何透過分子設計改變材料之光物理及電化學性質。第二章為有機太陽能電池之研究，以本實驗室林立彥博士於2012年發表之D-A-A型小分子染料 DTDCPB 進行改良，將中心拉電子基團苯并噻二唑分別改為吡啶噻二唑及具二氰基修飾之苯并噻二唑，設計出目標分子 DCPoPTD、DCPiPTD及 DTDCPDCBT。雖然尚未合成出 DTDCPDCBT，但DCPoPTD及DCPiPTD 相較於DTDCPB 確實如預期中吸光紅移、能隙縮小，目前以 DCPiPTD 混摻C70 所製成之太陽能電池元件於初步測試中有不錯的表現。第三章為雙光子吸收材料之研究，同樣以二氰基修飾之苯并噻二唑作為中心之拉電子基團，設計並合成出對稱結構之DDTDCBT，其具有較紅移之雙光子吸收。爾後為了提升有機分子於水中的溶解度，我們設計並合成出兩個具有新型推電子基團 MP 之分子 DMPPhBT 及 DMPPhDCBT，在分子設計上透過甲基化形成具水溶性之有機離子，提高其於生醫領域之應用性，目前也已經初步量測其雙光子激發螢光。第四章為有機發光二極體之研究，我們設計並合成出以二氰基修飾之喹喔啉為主體的電子傳輸材料56p-QN及56m-QN。此二電子傳輸層材料具有較低之分子能階，可與不同的電洞傳輸材料搭配以形成放光紅移之激態複合物系統，並具有不錯之螢光量子產率。將激態複合物系統與吸光波長匹配之螢光分子混摻製成有機發光二極體元件，其元件之放光位於近紅外光範圍，並擁有相當高之外部量子效率。

關鍵字

有機太陽能電池 ； 雙光子吸收材料 ； 有機發光二極體

並列摘要

In comparison to conventional inorganic materials, organic functional materials own several advantages, such as lower cost for mass production and mechanical flexibility of the devices. Moreover, according to different applications of organic functional materials, the photophysical and electrochemical properties of organic molecules could be elaborately adjusted by different designing strategies. Among different categories of organic functional materials, organic photovoltaics (OPVs), two-photon absorption (2PA) materials and organic light-emitting diodes (OLEDs) have attracted lots of attention due to their promising future. Organic photovoltaics, whose active layers are composed of organic molecules with strong extinction coefficient and high charge carrier mobility, has been thriving nowadays because of the depletion of nonrenewable energy resources. In opposite to organic photovoltaics, electric power is consumed for organic light-emitting diodes to generate light. In addition, for biomedical application, two-photon absorption materials are prominent due to their capability to absorb deep penetrating near-infrared light in the tissue.

In this thesis, the first chapter briefly introduces the history of OPVs, OLEDs and 2PA materials as well as some universal designing strategies of organic molecules to adjust their photophysical and electrochemical properties. In the second chapter, aiming at bathochromic absorption for efficient OPV devices, benzothiadiazole (BT) derivative-based small molecules were modified from previously reported D-A-A type molecule DTDCPB. While the synthesis of cyano-substituted DTDCPDCBT is not complete, thiadiazolo[3,4-c]pyridine (PTD) -based molecules DCPoPTD and DCPiPTD were synthesized and the effect of enhanced electron-withdrawing ability on bathochromic absorption has been corroborated. Moreover, the position of nitrogen atom on the PTD unit plays an important role in deciding the photophysical and electrochemical properties. By now, DCPiPTD-based OPV device could achieve PCE up to 6.6%, which is promising for further device optimization. The third chapter illustrates the design and syntheses of molecules utilized as two-photon absorption materials. In addition to cyano-substituted DDTDCBT, novel　1-methylpiperazine (MP) -based molecules DMPPhBT and DMPPhDCBT were designed to enhance the water solubility for biomedical application. 2PEF spectra of neutral molecules DDTDCBT, DMPPhBT, and DMPPhDCBT as well as organic counterion pairs DMPPhBT-MeI and DMPPhDCBT-MeI were preliminarily measured. In the last chapter, two quinoxaline-based molecules 56p-QN and 56m-QN were synthesized as electron acceptors for exciplex-based OLEDs. With elongated conjugated backbone attached by electron-withdrawing cyano groups, the energy levels of the two molecules are lowered significantly. Blend films of these two electron acceptors with appropriate electron donors exhibited exciplex characteristics with high photoluminescence quantum yields (PLQYs). Lastly, OLED devices based on these exciplex systems with suitable fluorescent emitters showed low turn-on voltages and relatively high external quantum efficiencies (EQE) among OLEDs in the range of near infrared emission.

並列關鍵字

Organic photovoltaics ； Two-photon absorption materials ； Organic light-emitting diodes

參考文獻

1.3 References

[1] Best Research-Cell Efficiency Chart. https://www.nrel.gov/pv/cell-efficiency.html (accessed Jul 6, 2020).

[2] Fang, P. H., J. Appl. Phys. 1974, 45, 4672-4673.

[3] Reucroft, P. J.; Takahashi, K.; Ullal, H., J. Appl. Phys. 1975, 46, 5218-5223.

[4] Tang, C. W., Appl. Phys. Lett. 1986, 48, 183-185.