中文摘要：

用密度泛函理论（DFT）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．

英文摘要：

Ground and excited state structures of several poly（p-phenylenevinylene） （PPV） oligomers that contain a biphenyl bridge were fully optimized by density functional theory （DFT） and the configuration interaction singles （CIS） method, respectively. The most rational geometric structures for the ground state, the excited state and frontier molecular orbitals were obtained. The absorption and emission properties of the oligomers were then calculated using the semi-empirical Zerner＇s intermediate neglect of differential overlap （ZINDO） and time-dependent density functional theory （TD-DFT）. We analyzed the effect of an increase in the biphenyl chain length on frontier molecular orbitals and the energy gap. Results indicate that absorption and emission properties hardly change as the length of the biphenyl chain increases. A cross configuration between neighboring PPV oligomer chains and the degree of intrachain twist becomes increasingly obvious. Molecular symmetry is reduced and the π-π stacking effect is weakened among these types of conjugated molecules in a solid. This is perhaps the most important factor for an increase in the fluorescence quantum efficiency of light-emitting diodes.