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

TL;DR

This paper presents 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 introduces a comprehensive theory linking magnetic fields to charge hopping and polaron density changes, explaining multiple magnetic-field effects in organic semiconductors.

Findings

Explains magnetic-field effects on photocurrent and luminescence.

Provides theoretical basis for empirical fitting formulas.

Unifies understanding of magnetic influences in organic semiconductors.

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 two hopping states are not too symmetric. 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.