The interface and bulk polarization effect of the single layer ferroelectric-like organic semiconductors on the current-voltage data

Abstract

It was shown recently that the hole current-density is in organic semiconductor structures modulated by the hole drift mobility, μd. It explicitly depends on the externally applied electric field, Ea, on the electric field at the hole-injecting electrode/organic interface, Eint, and on the Ea independent intrinsic hole drift mobility, μmax. Based on this relationship the published current-voltage measurements of two ferroelectric-like diode structures are examined. The on-state current-density of each diode is within the interval of Ea up to the value of the coercive electric field, EC, represented by the space-charge limited current, SCLC, specified by Ea independent, values of Eint and μmax. The polarization remains constant and small. Within the stated interval each off-state curve is described in terms of the linear Ea dependent Eint, which causes the polarization change. For Ea ≈ EC the current-density behavior depends on the location of the ferroelectric polarization within the sample. For the polarization confined within the volume of the electrode/organic interface then the off-state abruptly transits into the SCLC segment of the off-state curve that is followed by the steep unidentified current-density increase at the highest Ea to the intersection of both states. For the bulk polarized sample, the off-state close to EC deviates into the nearly linear Ea dependent current-density segment incorporating a weak Ea dependent hole density at the interface. The maximum difference between the off-, and on-states occur at Ea close to EC which is at about the point of the off-state interface polarization maxima.