Effects of electron-electron interactions on the dynamic recombination of on-chain polaron pair and off-chain counterion in conjugated polymers

¹ College of Information Science and Engineering, Hebei Engineering Research Center for Information Technology in Population Health, Hebei North University - Zhangjiakou 075000, China
² School of Electronic Engineering, Xidian University - Xian 710126, China
³ College of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University Shijiazhuang 050024, China
⁴ Department of Physics, Xingtai University - Xingtai 054001, China

^(a) zjkwangyadong@sina.com
^(b) my882154@126.com

Received: 11 July 2018
Accepted: 10 August 2018

Abstract

Combining the one-dimensional Su-Schrieffer-Heeger model and the extended Hubbard model, we investigate the dynamic recombination of an on-chain same charged polaron pair with an off-chain counterion trapped in an impurity molecule. We demonstrate that the bipolaron, the exciton and the trion are the main products in the polaron pair-counterion reaction and their yields depend sensitively on the electron-electron interactions. In general, the on-site Coulomb interactions favor the creation of the exciton while the nearest-neighbor interactions favor the creation of the bipolaron. However, the trion can also be formed directly with high yield via the polaron pair-counterion recombination by taking appropriate electron-electron interactions, which indicates that the trion formation model proposed by Kadashchuk et al. is a feasible and effective channel. Furthermore, we found that the yield of trion is proportional to the amount of charge trapped in the impurity injected into the main chain. Our findings show that the electron-electron interactions play a key role in the dynamic recombination of elementary excitations in a conjugated polymer.