We investigate the non-radiative decay process of diphenyldibenzofulvene (DPDBF) in solid phase by using the quantum chemistry methods. To carry out the non-radiative rate constant calculation, we construct a solid phase model based on ONIOM method. The geometry of DPDBF molecule is optimized for the ground state by DFT and the first excited state by TD-DFT and the corresponding vibrational frequencies and normal coordinates are computed. Under displaced-distorted harmonic oscillator potential approximation, Huang-Rhys factors are obtained. Vibronic coupling constants are calculated as a function of the normal mode based on Domcke's scheme. We find that vibronic coupling constants of 12 modes with large reorganization energies are similar order and if this result is still valid for other modes, the internal conversion rate would be determined by high frequency modes because they have significant nuclear part that is related to Franck-Condon overlap integrals. We also find that geometrical changes are suppressed due to the stacking effect, which yielding small Huang-Rhys values in solid phase.

本論文敘述雙苯環二苯富烯分子之光學性質的理論研究。雙苯環二苯富烯分子具有一種特別的光學性質，稱為堆積誘導發光(Aggretation Induced Emission)。這樣的性質之所以特別，原因在於有機化學家已普遍相信，當化合物從溶液態相變化成固體態時，隨著分子濃度的增加，會由於碰撞效應等因素，使化合物的發光能力衰落。化學家們把這種現象稱作是堆積誘導發光。由於堆積誘導發光化合物這種隨分子濃度增加，反而較易發光的特性，使它們在光伏特電池、有機發光二極體以及蛋白質偵測上，具有良好的表現。為探討AIE的機制，有機化學家與理論計算學家攜手合作，他們發現具有堆積誘導發光性質的化合物，在溶液狀態與在固體狀態的發光速率(radiative rate)相差不大，因此他們認為：堆積誘導發光化合物在溶液狀態與固體狀態之螢光產率的差異，很可能是來自非發光速率(non-radiative rate)不同。在文獻中，理論計算學家已提出系統在溶液狀態之非發光速率的計算方法，即在溶液狀態必須考慮模式混合效應(Duschinsky rotation effect)。然而，對於系統在固體狀態之非發光速率的計算方式卻尚未被提及，因此，在本文裡，我們以雙苯環二苯富烯為研究體系，提出一個系統在固體狀態之非發光速率的計算方式：我們使用位移-扭曲簡諧位能面的假設，將文獻中的非發光速率計算公式加以推廣，使其能運用在多種振動模式(Multi-modes)，再搭配執行固態模擬所得的參數，進而得到系統在固體狀態之非發光速率。

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