A General Charge Transport Picture for Organic Semiconductors with Nonlocal Electron-Phonon Couplings

TL;DR

This paper presents a comprehensive numerical study of charge transport in organic semiconductors, unifying different transport regimes and identifying an intermediate regime where traditional models do not apply.

Contribution

It introduces a nearly exact numerical approach to map out various charge transport regimes in the Holstein-Peierls model, revealing an intermediate regime beyond existing theories.

Findings

Identification of distinct transport regimes (phonon-assisted, transient localization, band-like)

Discovery of an intermediate regime where none of the traditional models apply

Limited applicability of the hopping regime in the proposed paradigm

Abstract

The nonlocal electron-phonon couplings in organic semiconductors responsible for the fluctuation of intermolecular transfer integrals has been the center of interest recently. Several irreconcilable scenarios coexist for the description of the nonlocal electron-phonon coupling, such as phonon-assisted transport, transient localization, and band-like transport. Through a nearly exact numerical study for the carrier mobility of the Holstein-Peierls model using the matrix product states approach, we locate the phonon-assisted transport, transient localization and band-like regimes as a function of the transfer integral ($V$) and the nonlocal electron-phonon couplings ($\Delta V$), and their distinct transport behaviors are analyzed by carrier mobility, mean free path, optical conductivity and one-particle spectral function. We also identify an "intermediate regime" where none of the established pictures applies, and the generally perceived hopping regime is found to be at a very limited end in the proposed regime paradigm.