電致變色是材料的光學性質，在外加電壓的作用下改變而產生的可逆顏色變化的現象
近年來，電致變色材料（EC）及其電致變色元件（ECD）的研究受到高度的關注，可應用於智能窗戶，汽車後鏡子，安全頭盔和顯示器等各個領域。在不同種類的EC材料中，有機分子紫精（1-1'-二取代-4,4'-聯吡啶）在電化學和光電化學過程中作為氧化還原對，透過可逆的單電子還原可以形成非常穩定的自由基陽離子。但是，現今大多數電致變色材料因本身性質的因素，只能考慮單一方向上應用，例如只有單一還原或單一氧化，這導致在應用上有許多的限制。因此，開發出合適的EC材料對於新一代電致變色器件至關重要。高性能EC材料主要應具有多色特性，長期穩定性，易加工性和快速響應時間。在論文中，我們主要的目標是開發可用於還原和氧化過程的新型電致變色材料。
本研究以有機電致變色材料為主軸，利用Gaussian09中的密度泛函理論（DFT）及時間相依密度泛函理論（TD-DFT）進行電致變色材料的分析，研究了它們的電化學和光學性質，藉由改變材料的共振配體（conjugation group）、推電子基(electron donating group)及分子間的共振強度(  spacer)，系統性的分析並提出能提升電致變色材料光電強度的策略。此外，我們還探討了不同強度的推電子基的效應以及溶劑對氧化和還原過程中對整體電致變色的影響。計算結果顯示所設計的單體具有清晰的顏色轉換在氧化還原過程中
。當引入更強的推電子基團和更強的 spacer在第二氧化態中有新的長波長(NIR)吸收峰產生。因此，可增加其應用性。透過本研究，吾人更加了解不同取代基在整體電致變色材料中所扮演的角色，以及發展出可同時用於氧化及還原型態的新型電致變色材料，有助於未來的電致變色材料之設計及應用，本研究希望除了透過傳統實驗的分析之外，從理論計算的角度出發，提出新的觀點供其他學者參考。

Electrochromism is the property of a material to reversibly change the color as a result of electrochemical oxidation or reduction driven by electrical bias. Recently, studies on electrochromic materials (EC) and designing suitable electrochromic devices (ECD) has attracted great attention because of their potential applications in various fields such as smart windows, mirrors, safety helmets, and displays. Among the different kind of EC materials, viologen (1-1’-disubstituted-4,4’-bipyridinum) is used as a redox couple in many electrochemical and photoelectrochemical processes, since it undergoes reversible one-electron reductions and formed very stable radical cations at very low potential. However, most of the electrochromic materials can only be used in the one direction such as either reduction or oxidation process, which resulted in only one color state. Thus, finding suitable EC materials is essential in developing a new generation of electrochromic devices. A high-performance EC material primarily should possess multicolored characteristics, long-term stability, easy processing and rapid response time. Keeping in mind, In this study, we aimed to develop the novel electrochromic materials which can be used in both reduction and oxidation processes.
In this study, we propose a simple linkage approach by merging ambipolar EC materials in both -acceptor- (-A-) and donor-acceptor-donor (D-A-D) configurations composed of Anthracene, Toluene, and Pyrene as -conjugated molecules, TPA as a donor and viologen as an acceptor moiety investigated their electrochemical and spectroelectrochemical properties using density functional theory calculations. Furthermore, we also explored the substitutional effects in donor moiety as well as the different solvents on the overall electrochromism during both oxidation and reduction processes using. Here mainly we focused the relationship between the structure, functional group’s electronic and spectral properties, as well as redox potential of designed monomers. Our calculations indicate that designed monomers have attractive absorption properties, and show clear color switching upon the redox process. Besides, introducing stronger electron donating group and stronger -spacer cause the new absorption peaks in the second oxidation states. These designed viologen derivatives will be potential candidates, which can be used in both oxidation and reduction processes for upcoming electrochromic devices.

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