Magnetoconductance responses in organic charge-transfer-complex molecules

Blending 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), a high electron affinity organic molecule, with N,N′-bis-(1-naphyl)-N,N′-diphenyl-1,1′-biphenyl′-4,4′-diamine (NPB) creates the charge-transfer-complex molecules and modulates the magnetoconductance (MC) responses of devices by an applied electrical bias. A negative MC response (−0.60%) is observed for the device made of NPB:F4-TCNQ(30%) film as the active layer, which has a distinct characteristic to negligible MC responses in pristine NPB- and F4-TCNQ-based devices. We attribute the MC responses to the magnetic-field-dependent transport of injected charge carriers through charge-transfer-complex molecules in the NPB:F4-TCNQ system, which are varied with the F4-TCNQ blending concentrations and the injection of minority charge carriers. Results of this study demonstrate a turning point of MC responses at the bias voltage near the threshold of the bipolar injection.