太陽能電池材料( bulk heterojunction, BHJ )需含有良好的共振系統，過去數十年來已有許多科學家嘗試出合成不同的化合物，然而在予體-受體這一類型的共軛聚合物方面，受體強度的影響似乎沒有廣泛的探討。本論文主要著重於計算( Dimethoxyphenylene與Fluorene )為予體在與不同受體所形成的寡聚物與共聚物而應用於異質接面( BHJ )太陽能電池的研究。 本文以2,5-dimethyloxyphenylene( DMOP )與flourene( F )為主體(予體)，設計出八種不同的受體而形成寡聚物與共聚物。以DFT/B3LYP搭配6-31G*的基底函數計算結構的最佳化，經由理論計算結果來探討，當予體接上不同受體( X )時，結構會依照受體的強弱大小而造成兩面角的改變；接著選用三種計算方法( DFT、TD-DFT與ZINDO )，對單體與寡聚物做EHOMO、ELUMO與EGAP，會得到三種不同的能隙值Eg( DFT )、Eg( TD )和Eg( ZINDO )，當單體數增加時，Eg( DFT )、Eg( TD )和Eg( ZINDO )的能隙值都會逐漸降低，而寡聚物的能隙值也會依照受體強度的變化而有所變動，再將n = 1~4的能隙值由外插法求得共聚物的能隙值，以外插法計算的三種方法DFT、TD-DFT、ZINDO中，以TD-DFT計算結果的能隙值與實驗值較接近。寡聚物的吸收光譜也會因受體的改變而影響最大波長的分布情況與吸光範圍。經由能隙與光譜相互比較的結果，找出五種共聚物PDMOPTP、PDMOPDTTP、PDMOPDTBT、PFTP與PFDTTP其能隙值都介於1.40~1.90eV之間，且吸收波長都在可見光區甚至有些共聚物以達到紅外光的範圍，對於異質接面( BHJ )太陽能電池中也許會是一種具有發展性的材料。 Recently, donor-acceptor (D-A) conjugated copolymers have attracted considerable attention because their electronic and optoelectronic properties could be efficiently tuned by intramolecular charge transfer (ICT). However, the effects of acceptor strengths on the electronic and optoelectronic properties of donor-acceptor and donor-acceptor-donor copolymers have not been fully explored. Our study on the 2,5-dimethyloxyphenylene (DMOP) and fluorine (F)-based donor-acceptor polymers showed that the hole mobility was controlled by the acceptor strength and backbone coplanarity in the bulkheterojunction (BHJ) solar cell device. We had selected eight donor-acceptor system and thiophene-acceptor-thiophene monomers/oligomers to investigate their electrochemical and photophysical properties. The geometrical structures and electronic properties of both monomers and oligomers are studied using three kinds of calculation methods. One, we used density functional theory (DFT/B3LYP) to calculate HOMO energies, LUMO energies and the HOMO-LUMO gaps (Eg) of these polymers. The lowest excitation energies and the maximal absorption wavelength λabs of the oligomers of these polymers and studied employing the time-dependent density functional theory (TDDFT) and semi-empirical method (ZINDO). According to our calculating result, some copolymers such as PDMOPTP, PDMOPDTTP, PDMOPDTBT, PFTP and PFDTTP exhibit more lower HOMO-LUMO gaps (Eg) than others and their absorption spectra can reach visible light to near-infrared region. Therefore we show five kinds of copolymers may be applied to the electron-donating materials in BHJ solar cells.
