吡咯并吡咯二酮与低聚噻吩共聚物电荷传输性质的理论研究

利用密度泛函理论对吡咯并吡咯二酮(DPP)与噻吩形成共聚物的低聚物(PDPP-n T)m的电子结构及二体堆积模型的电荷传输性质进行计算.结果表明,随着聚合物单元内DPP浓度增加,噻吩数减少,聚合物分子的HOMO和LUMO能级同时降低,并且HOMO-LUMO带隙变小;链内相邻DPP单元的电子波函数有效重叠增大,显著改善了链内的电子传输能力;同时分子主链的刚性增强,使分子链间LUMO轨道重叠增强,电子转移积分增大;最终体系由p型向双极性材料转化.

Theoretical Study on Charge Transport Properties of Copolymers of Diketopyrrolopyrrole and Oligo-thiophene

The electronic structures and charge transport properties of the oligomers of diketopyrrolopyrrole ( DPP ) with the thiophene were investigated with ab initio density functional theory and classical Marcus charge transport theory. The results show that with the increase of the DPP concentration( or decrease of the thiophene numbers) in the polymer unit both the HOMO and LUMO energy levels of the polymers decrease, and the band gaps narrow. As the DPP concentration increased, the intrachain overlap of the electron wave functions of the DPP acceptor units was improved, that facilitates the intrachain electron transport. Moreover, the increase of DPP concentration strengthens the rigidity of the molecular backbone and enhances the interchain overlap of LUMO orbitals, which strengthens the electron transfer integrals and the system is conver-ted from p-type into ambipolar materials.