中文摘要：

以2,4′-聚噻唑,聚噻吩以及噻吩噻唑两嵌段聚合物分子为研究对象,利用第一性原理计算方法和非平衡格林函数理论,研究了分子极性对分子结器件的电输运性质的影响.计算结果表明,噻唑单元在输运方向上存在分子偶极矩,从而导致在含有噻唑单元的2,4′-聚噻唑和噻吩噻唑两嵌段聚合物的分子结中产生电流整流效应.两种分子结的整流比率分别达到38（2.0V）和24（1.4V）.通过对外场下能级的偏移和分子轨道在实空间扩展性变化的分析,对分子结中整流现象进行了详细的阐述.

英文摘要：

Transport properties of three typical molecular junctions which contain polythiazoles（PTz）,polythiophenes（PTh） homopolymers and diblock oligomer（DBO） are studied theoretically by combining Density Functional Theory（DFT） and Nonequilibrium Green Function（NEGF） method.There is strong rectification effect in PTz and DBO molecular junction respectively which is the result of molecular dipole moment of thiazole unit in the transport direction.The rectification ratios 38 at 2.0 V for PTz and 24 at 1.4 V for DBO have been obtained.By analyzing the changes of the transmission spectrum and MPSH states with external electrical field,we find that rectification characteristics of I-V is due to both the energy levels shifts of the extended molecule and the localization properties of the MPSH orbital of the corresponding energy level in an electric field.