Voltage Dependence of Magnetoconductance in Organic Semiconductor Devices

We study the voltage effect on magnetoconductance (MC) in an organic semiconductor device based on voltage-related carrier density and mobility. With the effects of magnetic field and hyperfine interaction, we present the transition between polaron and bipolarons, and provide the dependence of MC on total carrier density and mobility. The MC effect will become weak with increasing voltage in a unipolar polymer device and the sign of MC will change at a critical voltage. In a small molecular device, the situation is opposite: MC increases with increasing voltage. Furthermore, our theoretical calculations are well consistent with the experimental results. (C) 2013 The Japan Society of Applied Physics