π桥(π=Py、Tz、THF)对聚吡咯并吡咯二酮-联噻吩光电性能影响的第一性原理研究

First-principles Study on the Effect ofπBridge(π=Py,Tz,THF)on the Photoelectric Property of Polymer Polydiketopyrrolopyrrole-bithiophene

本文在聚吡咯并吡咯二酮-联噻吩(PDPP-2T,P1)的基础上,分别选取了吡啶(Py)、噻唑(Tz)、呋喃(THF)三种基团构造D-π-A共聚物P2、P3、P4,并通过密度泛函(DFT)第一性原理计算了四种聚合物的光电性质。计算结果表明,引入π桥后,能带曲率变大,有利于提升共聚物导电性,但带隙均增大;光吸收峰的短波吸收峰均发生红移,P2与P4的长波峰发生蓝移,而P3的长波峰变化不大,且长波吸收峰的强度均减弱。并用Bader电荷分析研究了三种π桥对D、A单元之间的电荷转移量的影响,发现引入π桥后,P2、P3电荷转移量减少,P4略微增加;且π桥在共聚物中既可以是得电子单元,又可以是失电子单元,表明引入π桥对D/A共聚物的电荷传输有一定影响。总之,用引入π桥的方法来提升共聚物的光电性质是一个需综合考虑的问题。

In this paper,on the basis of polydiketopyrrolopyrrole-bithiophene(PDPP-2T,P1),three groups of pyridine(Py),thiazole(Tz),and furan(THF)were selected to construct a D-π-A copolymer P2,P3,P4,and the photoelectric properties of the four polymers were calculated by the first-principle of density functional(DFT).The calculation results show that the band curvature becomes larger after the introduction of theπbridge,which is helpful to improve the conductivity of the copolymer,but the band gap increases.The short-wave absorption peaks of the light absorption peak are red-shift,and the long-wave peaks of P2 and P4 are blue shift,while the long-wave peak of P3 does not change much.And the intensity of the long-wave absorption peak is weakened.The influence of three kinds ofπbridges on the charge transfer between D and A units was studied by Bader charge analysis.It was found that the charge transfers of P2 and P3 decreases and P4 increases slightly after the introduction ofπbridges.It is an gain-electron unit or a loss-electron unit,which shows that the introduction of aπbridge has a certain effect on the charge transport of the D/A copolymer.In short,it is a problem that needs to be considered comprehensively to increase the photoelectric properties of the copolymer by introducing aπbridge.