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

¹ Physics Department, The Hong Kong University of Science and Technology - Clear Water Bay, Hong Kong SAR, China
² School of Physics, National Key Laboratory of Crystal Materials, Shandong University - Jinan, Shandong, 250100, China

^a phxwan@ust.hk
^b xsj@sdu.edu.cn

Received: 14 September 2010
Accepted: 12 November 2010

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 polaron 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 investigation indicates a convincing new mechanism for organic magnetic-field effect.