Wave-packet multi-scale simulations based on a non-linear tight-binding Hamiltonian for carrier transport in π-conjugated polymers

Abstract

We proposed a multi-scale computational framework based on a wave-packet propagation with a non-linear tight-binding Hückel model and molecular dynamics with a density functional method, and adopted the multi-scale approach to carrier transport of organic polymers showing dynamic structural fluctuations. In the tight-binding Hückel Hamiltonian, we introduced an electron–hole binding energy, the non-linear term in the present method, and investigated the influence of the electron–hole binding on the carrier mobility. We conducted wave-packet propagation for 5 ps dynamics on two kinds of polymers with 1 μm length. We found that when the electron–hole binding energy is changed from 0 to 500 meV, the carrier mobility can be changed by two orders of magnitude. We also analyzed the localization property of the wave-packet on the polymers, and found that (1) in both small and large electron–hole binding regimes, the orbital localization simply causes the decrease in carrier mobility, and (2) in an intermediate electron–hole binding regime, the orbital localization rather enhances the carrier mobility.