Non-equilibrium charge transport in a conjugated polymer

Xiao Cheng; Hui Zhao; Hang Xie

doi:10.1088/1361-648X/abd811

Non-equilibrium charge transport in a conjugated polymer

J Phys Condens Matter. 2021 Jan 25;33(13). doi: 10.1088/1361-648X/abd811.

Authors

Xiao Cheng¹, Hui Zhao², Hang Xie¹

Affiliations

¹ Department of Physics, Chongqing University, Chongqing 401331, People's Republic of China.
² School of Physical Science and Engineering, Tongji University, 20092, People's Republic of China.

PMID: 33395677
DOI: 10.1088/1361-648X/abd811

Abstract

To address the non-equilibrium transport mechanism in a conjugated polymer, we investigate the dynamics of the lattice deformation and the charge transport in a polymer chain coupled with the reservoirs by the time-dependent non-equilibrium Green's function formulism. We find that the delocalized soliton lattice wave (SLW) forms in the polymer, rather than the well-known localized excitations such as polarons and solitons. The source reservoir drives an electron-like transient dynamic SLW while the drain reservoir drives the hole-like one. These transient SLWs propagate in opposite directions and then merge and relax to a steady SLW. These results are confirmed by our analytical derivation based on the continuum model. When the bias voltages are symmetric (μ_L= -μ_R), the dynamic SLW subsides to the stationary soliton lattice (SL). In the energy domain, the sandwich-structured non-full filled SL bands form in the original gap, which can provide the conduction channels. Especially, in the case of the symmetric bias voltages (μ_L= -μ_R), the SL band is half-filled. The transmission current is the major part of the total current and the rest minor part is the effective current induced by the charge density waves accompanied by the SLW.

Keywords: conjugated polymer; non-equilibrium transport; soliton lattice.