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A Time-Dependent DFT Study of the absorption and Fluorescence Properties of Pyrene-Fused N-Heteroacene

A Time-Dependent DFT Study of the Absorption and Fluorescenc...

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第十三届全国量子化学会议

作者： Huanxiang Zhang Wei Hao Zilong Wang Jia Zhu Qichun Zhang Shuzhou Li Department of Chemistry Beijing Normal University School of Materials Science and Engineering Nanyang Technological University

absorption and fluorescence spectra of Pyrene-Fused N-Heteroacene(Ring12 and Ring15) have been computed by using time-dependent density functional theory(TDDFT). From the calculated frontier molecular orbitals, we can see the electron distribution of LUMO orbital is more delocalized than HOMO orbital and the substituents on Si has not great contribution to electron transfer. In order to explore the impact of different substituents and simplify the calculation model, we calculated the absorption and fluorescence properties of Ring12 and Ring15 by adding the substituents gradually. Our results shows that the number of methyl groups attached to Si has a particularly small effect on the absorption wavelength no matter in Ring12 or Ring15. At the same time the difference of band gap is very small. And because the HOMO is mainly localized over the two thiophene moieties but the LUMO is delocalized throughout the entire molecular backbone, absorption and emission intensity is small. Interestingly, when substituted with a strong electron-withdrawing group1 such as –COOH in Ring12, the band gap is reduced and thus presents a large redshift(about 180 nm)in absorption wavelength. From our calculations,we can obtain the influence of the number of different substituents on the absorption and emission wavelengths about the Pyrene-Fused N-Heteroacene and the results have important consequences about simplify computation of Pyrene-Fused N-Heteroacene.

关键词： Pyrene-Fused N-Heteroacene absorption wavelength TDDFT

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苯并[1,2-b:4,5-b｀]二噻吩共聚物光伏材料的光电性能的理论研究(英文)

苯并[1,2-b:4,5-b｀]二噻吩共聚物光伏材料的光电性能的理论研究(...

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第十届全国计算(机)化学学术会议

作者：彭月明王学业王暖庆郑小燕易山峰湘潭大学化学学院环境友好化学与应用省部共建教育部重点实验室

Since the absorption spectra and hole mobility of conjugated polymer donor materials are the major factors that affect the power conversion efficieny(PCE) of polymer solar cells (PSCs),in order to predict absorption band and the hole mobility for guiding the synthesis of novel materials with broader absorption band and higher hole mobility for improving the photovoltaic properties of the conjugated polymers,quantum-chemical techniques are employed to calculate the absorption spectra and energy gaps of benzo[1,2- b:4,5-b’]dithiophene(BDT) with different conjugated units,namely,poly(4,8-bis(dodecyloxy) benzo[1,2-b:4,5-b’]dithiophene)(H2),poly(4,8-bis(do- decyloxy) benzo[1,2-b:4,5-b’]dithiophene)-alt-(2,5-thiophene)(H6),poly(4,8-bis(dodecyloxy) benzo[1,2-b:4,5-b’]dithiophene)-alt-(2,9-thieno[3,4-b]pyrazine)(H9).In addition to HOMO-LUMO gaps(Δ),geometries optimized,electronic properties of the neutral molecules are studied using the B3LYP *** lowest excitation energies(E) and the maximal absorption wavelength(λ) of(H),(H6)and(H9) are investigated by employing time-dependent density functional theory(TD-DFT).Δ and E values of each polymer are obtained by extrapolating those of the oligomers to the inverse chain length equal to zero(1/n=0). When introduced electron-donating unit and electron-deficient unit are introduced into BDT,their energy gaps,HOMO and LUMO energy levels of the polymers are tuned *** effects lead to a reduction of the energy barrier for the injection of holes in related polymeric photovoltaic devices and should contribute to the enhancement of their performances.

关键词： absorption wavelength energy gap photovoltaic materials polymer time-dependent density functional theory(TD-DFT)

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