密度泛函理论研究2种新型染料分子的分子内电荷转移现象

DFT study on intermolecular charge transfer in two novel dye molecules for organic solar cell

采用量子化学方法研究了2种新型有机染料分子P1和P4,几何优化和基态性质计算采用B3LYP密度泛函,基组为6-311G(d).由于P1和P4分子中分别存在2个对称的吸电子基团,所以2个染料分子的电子结构存在明显的特点:2个紧邻简并最低空轨道(LowestUnoccupied Molecular Orbital,LUMO)轨道.P1和P4最高占据轨道(Highest Occupied Mo-lecular Orbital,HOMO)到LUMO轨道的跃迁能级差分别为2.79和3.26eV.同时,采用含时密度泛函方法(Time-Dependent Density Functional Theory,TDDFT)研究了2个染料分子的激发态性质.通过电荷差异密度理论方法(Charge Different Density,CDD)直观的展示了分子内电荷转移的现象.对于P1,电荷转移的方向是从苯甲酸基团到2个二氰乙烯基噻吩苯基团;对于P4,电荷是由2个二氰乙烯基联苯基团基团向苯甲酸基转移.

Two novel organic dyes（P1,P4） for organic solar cell were investigated by means of quantum-chemical calculations.Optimized geometries of two dyes and their ground state properties were studied at the B3LYP/6-311G（d） level.Because of the two configurationally symmetric acceptors,an obvious characteristic of the electronic structure is the two near-degenerate LUMO level.For HOMO→LUMO transition,the energy level differences of P1 and P4 is about 2.79 and 3.26 eV,respectively.Excited-state properties of two dyes were investigated using time-dependent density functional theory（TD-DFT）.Charge of P1 is transferred from the benzoic acid moiety to dicyano-vinyl thiophene-2-yl phenyl moiety;charge of P4 is transferred from dicyano-vinyl biphenyl moiety to benzoic acid moiety by means of charge different density（CDD） method.