给电子基团对吲哚染料电子结构和吸收光谱的影响

摘要

利用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT),分别基于B3LYP和PBE1PBE方法研究了一系列含有不同给电子基团的吲哚染料分子(ID1-ID3)的电子结构和吸收光谱性质.重点比较了不同电子给体对染料的分子结构、吸收光谱以及其在电池中的光伏性能的影响.结果表明从ID1、ID2到ID3,随着电子给体中苯环数日的增加,吲哚分子上的共轭效应逐渐增大,导致吲哚分子最高占据分子轨道-最低未占据分子轨道(HOMO-LUMO)之间的能隙变窄,分子的吸收光谱发生红移.染料分子的吸收光谱和LUMO能级分别影响染料的吸光效率和光电转化过程中电子的注入过程,从而使其二者成为决定电池光伏性能的重要参数.综合考虑上述两个参数对电池性能的贡献,通过理论研究证实,在ID1-ID3系列染料中,ID3具有较长的吸收谱带、较大的分子消光系数和合适的LUMO能级,从而表现出最为优越的光伏性能,这与实验得出的结论很好地吻合.%The electronic structures and absorption spectra of indoline dyes containing different donors (ID1 -ID3) were investigated by density functional theory (DFT) and time-dependent DFT,at the B3LYP and PBEIPBE levels,respectively.The effects of the donor moieties on the molecular structures,absorption spectra,and photovoltaic performance have been compared.The results indicate the increase in the number of phenyl groups in the donor decreases the highest occupied molecular orbital-the lowest unoccupied molecular orbital (HOMO-LUMO) energy gap and red-shifts the absorption band.This is related to the increased conjugation from ID1 to ID2 and ID3.The absorption spectra and LUMO energy level act as two criteria for the photovoltaic performance of a dye by determining the light harvesting efficiency and charge injection process,respectively.Considering the above two factors' contribution to the performance of a photovoltaic cell,ID3 with a long absorption band and high extinction coefficient,as well as a favorable LUMO energy level has been confirmed theoretically to be the best dye of ID1-ID3,which is consistent with experiment results.