電子振動耦合在分子激發態之理論及其在有機光電材料上之應用

Abstract

分子的電子振動耦合在光化學過程中扮演著重要的角色，例如：分子內轉換、系間轉換、電子轉移等，其耦合帶動著激發態分子由高的振動能級降到最低的振動能級，此分子振動弛豫過程是分子激發態能量耗散的重要途徑之一，若能降低此能量耗散效應，將有助於提高發光量子產率，進而發展出高效能有機光電材料。因此，本論文將從理論與計算化學的角度出發，利用密度泛函理論探討不同分子系統在弛豫過程中的重組能，以期能更深入了解電子振動耦合在激發態動力學中所扮演的角色。 本論文主要分為三個篇章，分別針對電子振動耦合在分子激發態的基礎理論和其在有機光電材料之應用做探討： (一)、分析多環芳香烴在不同激發態的電子振動耦合，進而發現調控分子內重組能之設計原則； (二)、近紅外發光材料中，單體和二聚體的鉑金屬錯合物之分子內重組能分析； (三)、發展單重態激發分裂(singlet fission)過程的電子振動耦合計算方法。 本論文所提出的觀點，將有助於了解電子振動耦合對於不同類型的有機光電材料之影響，進而藉由調控分子內重組能以提高其材料效能。

Vibronic coupling in the molecular excited states is one of the central concepts in the photochemical process, which is related to the internal conversion, intersystem crossing, energy transfer, and electron transfer. The strength of vibronic coupling determines the energy cost in the vibrational relaxation process which is called the internal reorganization energy. Reducing this energy dissipation in the excited state would helpful for increasing the luminescence quantum yield. In this thesis, we use DFT calculations to estimate the vibronic coupling in the different molecular systems. Three topics are independently studied: (a) investigation of polycyclic aromatic hydrocarbons with different vibronic coupling strengths in the lowest three excited states, (b) analysis of the reorganization energy of Pt(II) complex in monomer and dimer forms, and (c) development of a new methodology to estimate the vibronic couplings in the excited states associated with singlet fission process. The acquired knowledge from this thesis enabled us to elucidate the strength of vibronic coupling in the various systems. Furthermore, from the viewpoint of the reorganization energy, we provide valuable design principles to explore the high-performance optoelectronic materials.