富勒烯衍生物苯基C_(71)-丁酸甲酯的结构和电学性质第一性原理研究

First principles calculations of structure and the electronic properties of fullerene derivative phenyl-C_(71)-butyric acid methyl ester

使用B3LYP/6-31G(d)方法对有机太阳电池中作为电子受体材料的富勒烯衍生物苯基C71-丁酸甲酯([70]PCBM)的同分异构体进行了计算.PCBM与C70通过六元环和六元环共用的CC双键加成得到的产物是热力学控制产物;通过五元环和六元环共用的C—C键加成得到的产物则是动力学控制产物.[70]PCBM与C70的第一绝热电子亲和势很接近.PCBM对前线轨道贡献很小,[70]PCBM的最高占据分子轨道和最低未占据分子轨道(LUMO)的电子云主要分布在C70笼上.PCBM提升了C70的LUMO能级水平,有利于提高太阳电池的光电转换效率.自然布居分析表明,PCBM与C70之间没有发生显著的电荷转移.所有的性质研究表明,PCBM基团并不涉及电池光电转换过程,但在调整C70能级水平提高光电转换效率中发挥了重要作用.

Phenyl-C71 -butyric acid methyl ester （[ 70] PCBM） clusters are investigated by using the B3LYP method with 6-31G（d） basis set. The optimized results indicate that the addition of PCBM into the [6,6 ]-junction produces a closed methanofullerene which is thermodynamically stable product; and the addition into the [ 5,6]-junction results in an enlarged fullerene （an open fulleroid） which is a kinetically controlled product. The first adiabatic electron affinity for [70]PCBM is similar to that for C70. The energy gaps of [70] PCBM are reduced compared with those of C70. PCBM derivatives and show increased level of the lowest unoccupied molecular orbital of fullerenes. From the natural charge populations, it is found that adding PCBM unit onto the C70 cages does not change the charge populations remarkably; attaching a PCBM has no effect on the electronic structures of C70. The results of theoretical calculation suggest that PCBM is not involved in the process of photoelectric conversion but it plays a key role in adjusting the level of HOMO-LUMO for increasing photoelectric conversion efficiencies.