【作者】 刘俊娟；

【导师】 安忠；

【作者基本信息】 河北师范大学 ， 凝聚态物理， 2008， 硕士

【摘要】 基于一维紧束缚SSH模型,采用非绝热动力学方法,我们研究了:1.掺杂聚合物的静态性质以及杂质离子对极化子动力学过程的影响。(1)在聚合物中均匀加入杂质离子的数目不同,则聚合物材料带隙的宽度不同;随着杂质势强度的增加,带隙变得越来越窄;(2)在聚合物中加入相同的杂质势(VP>0),发现杂质离子对电子极化子和空穴极化子的运动速度影响不同。在电场下极化子被加速,达到饱和速度后与杂质离子发生碰撞,电子极化子与杂质离子(VP>0)碰撞时受到库仑排斥作用,类似于势垒;而空穴极化子与杂质离子(VP>0)碰撞时受到库仑吸引作用,类似于势阱,由于杂质离子对正负极化子的作用不同,造成了它们平均速度的差异。(3)正负极化子的平均速度与杂质离子之间的距离有关。当杂质离子之间距离较近时,如,两杂质离子相距六倍晶格常数距离时,电子极化子的平均速度远快于空穴极化子。此外,正负极化子的平均速度还随着杂质势强度的增加而减少。2.含有侧基聚合物的静态性质以及侧基对极化子动力学过程的影响。(1)在聚合物链中引入具有排斥电子作用的侧基,侧基上的电子易跃迁至主链,相当于N型半导体材料。相反,如果用吸引电子基团作为聚合物的侧基,主链电子易跃迁至侧基,相当于P型半导体材料。侧基的加入使得聚合物带隙中形成局域能级,深能级随着主链与侧基之间跃迁积分的增加向带隙中间靠近,而随着其侧基基团在位能的增加分别向导带和价带靠近;(2)由于电子极化子和空穴极化子与侧基碰撞时受到的相互作用不同,导致了电子和空穴极化子运动速度不同。如,两侧基之间相距十六倍晶格常数时,极化子与侧基碰撞后,电子极化子的速度远快于空穴极化子。电子极化子的平均速度随着跃迁积分的增加而减少,相反,空穴极化子的平均速度随着跃迁积分的增加而增加;另外,侧基之间的距离对电子和空穴极化子平均速度的影响不同。随着侧基之间距离的增加,电子极化子的平均速度基本不变,而空穴极化子的平均速度在侧基之间的距离为14-22个晶格常数时,平均速度明显变小。电子和空穴极化子的平均速度还随着侧基基团在位能的变化而变化。更多还原

【Abstract】 Based on the one-dimensional tight-binding Su-Schrieffer-Heeger (SSH) model and by using a nonadiabatic molecular dynamic method, we studied some static properties of polymer and the dynamical process of polaron in a polymer chain.1. we investigated some static properties of polymer and the dynamical process of polaron in polymer with impurity ions. (1)It is found that the polymer band gap is different in polymer with different number of impurity ions. It is also found that the band gap of conjugated polymer decreases with the increasing of the impurities potential strength. (2) In polymer with the same impurity ions (VP>0), we found that the velocities of the electron and the hole polaron are different. The polaron is accelerated by an external electric field to arrive a stationary velocity, then the polaron will collide with impurities. There is the coulomb repulsion between electron polaron and impurity ions (VP>0), which is similar to the potential barrier, while there is the coulomb attraction between the hole polaron and impurity ions (VP>0), which is similar to the potential well. Electron and hole polaron have different coulomb interaction with impurity ions, which causes the polaron speed of plus and minus difference. (3)The average velocity of polaron is affected by the distance between impurity ions. When impurity ions have a little distance, for example, the distance of impurity ions is six times lattice constant, the average velocity of the electron polaron is faster than the hole polaron. In addition, it is found that the average velocity of polaron decreases with the increasing of impurities potential strength.2. We investigated some static properties of polymer and the dynamical process of polaron in a polymer chain with side radicals. (1) In the polymer chain with the electronic group with exclusion as side radicals, it is found that the electron is easy to transfer to the main chain, namely, N-type semiconductor material. On the contrary, if the electronic group with attractive replace side radicals, it is found that theπ-electron of the main chain is easy to transfer to the side radicals, namely, P-type semiconductor material. Local degenerate energy levels in the band gap are formed by adding the side radicals. Local energy levels approach to the center of the band gap with the increasing of the hopping integral (t1) between theπ-electron of the main chain and the unpaired electrons at the side radicals. And local energy levels approach to the valence band and conduction band with the increasing of the potential energy of the side radicals. (2) It is found that the velocities of the electron and the hole polaron are different due to the influence of side radicals, it is because polaron and side radicals have different interaction, which causes the polaron speed of plus and minus difference. The polaron is accelerated by an external electric field and arrives a stationary velocity, then the polaron will collide with the side radicals, when the distance of side radicals is sixteen times lattice constant, the velocity of the electron polaron is far faster than the hole polaron. It is shown that the average velocity of the electron polaron decreases with the increasing of the hopping integral (t1), but the average velocity of the hole polaron increases with the increasing of the hopping integral (t1). And it is found that the average velocity of the polaron is affected by the distance of side radicals, the average velocity of the electron polaron almost be a constant with the increasing of the distance of the side radicals, while the average velocity of the hole polaron decreases suddenly as the distance of the side radicals arrives 14-22 lattice constant. In addition, it is also found that the average velocity of the polaron relates to potential energy of the side radicals .更多还原