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用密度泛函理论(DPT)和单激发(CIS)方法分别对几种联苯桥联的聚对苯乙烯撑(PPV)齐聚物分子的基态结构和激发态结构进行全优化,得到基态与激发态分子的最优几何构型和前线分子轨道,并用半经验ZINDO(Zerner’s intermediate neglect of differential overlap)和含时密度泛函(TD-DFT)方法分别计算了各自的吸收光谱和发射光谱,分析了随着联苯链的增长前线分子轨道能级和能隙的变化以及对光电性能的影响.结果表明,联苯链的加长对吸收和发射性质影响不大,但在分子结构上由于PPV齐聚物(发光中心)链间交叉链内扭曲的构象越来越明显,降低了分子的平面性和对称性,减弱了这类共轭分子在固体中的π-π堆积作用,这可能是减少荧光猝灭效应,提高固体发光器件荧光量子效率的主要原因.
The density functional theory (DPT) and single excitation (CIS) methods were used to optimize the ground state and excited state structures of several biphenyl bridged poly (p-phenylenevinylene) (PPV) oligomers. The optimal geometries and frontier molecular orbitals of the excited state molecules were calculated and their respective absorption and emission spectra were calculated by Zerner’s intermediate neglect of differential overlap and time-dependent density functional (TD-DFT) With the increase of biphenyl chain frontier molecular orbital energy level and energy gap and the impact on the photoelectric properties of the results show that the extension of biphenyl chain absorption and emission properties of little, but in the molecular structure due to PPV The more conformational distortions in the cross-chain between chains of polymers (luminescent centers) reduce the planarity and symmetry of the molecules and reduce the π-π stacking effect of such conjugated molecules in solids, which may be a reduction Fluorescence quenching effect, the main reason to improve fluorescence quantum efficiency of solid-state light-emitting devices.