A theory for magnetic-field effects of nonmagnetic organic semiconducting materials

TL;DR

This paper introduces a universal theoretical mechanism explaining how weak magnetic fields influence charge transport and optical properties in nonmagnetic organic semiconductors, unifying various experimental observations.

Contribution

It presents a comprehensive theory that explains magnetic-field effects in organic semiconductors and supports empirical formulas used in the field.

Findings

Magnetic fields alter charge hopping coefficients between molecules.

Changes in hopping affect polaron density and device currents.

The theory explains diverse experimental phenomena.

Abstract

A universal mechanism for strong magnetic-field effects of nonmagnetic organic semiconductors is presented. A weak magnetic field (less than hundreds mT) can substantially change the charge carrier hopping coefficient between two neighboring organic molecules when the magnetic length is not too much longer than the molecule-molecule separation and localization length of electronic states involved. Under the illumination of lights or under a high electric field, the change of hopping coefficients leads also to the change of polaron density so that photocurrent, photoluminescence, electroluminescence, magnetoresistance and electrical-injection current become sensitive to a weak magnetic field. The present theory can not only explain all observed features, but also provide a solid theoretical basis for the widely used empirical fitting formulas.