By using displacement current measurement (DCM) and electric-field-induced optical second-harmonic generation (EFISHG) measurement, we studied the carrier behavior in the indium-tin oxide (ITO)/Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))/C60/Au(or Al) capacitors. Two DCM peaks appeared asymmetrically at around −35.5 V and +30.0 V in the dark. Correspondingly, the EFISHG response from the C60 layer was observed, but the peak positions were different with respect to DCM ones. The results show that the spontaneous polarization of the ferroelectric P(VDF-TrFE) polymeric layer directly affects the electric field in the C60 layer, and thus governs the carrier motion in this layer. As a result, the C60 layer serves like an insulator in the dark, while electrons and holes are captured and released at the interface in response to the turn-over of spontaneous polarization of ferroelectric layer. On the other hand, under white light illumination, C60 layer serves like a conductor due to the increase of photogenerated mobile carriers, and these carriers dominate the carrier motions therein. Our findings here will be helpful for analyzing carrier behaviors in organic electronic devices using ferroelectric polymers.

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The effect of ferroelectric polymer on carrier behaviors in indium–tin oxide (ITO)/poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)]/N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-(1,1′-biphenyl)-4,4′-diamine (α-NPD)/Au structure was investigated. The internal electric field in α-NPD introduced by the dipole moments from ferroelectric P(VDF–TrFE) together with the α-NPD/P(VDF–TrFE) interface accumulated charges plays an important role in the carrier motion in α-NPD. In displacement current measurement (DCM), two asymmetric peaks and reduced polarization resulting from a large injection barrier from Au electrode to α-NPD layer were observed. Coupled with the electric-field-induced optical second-harmonic generation (EFISHG) measurement, the electric field in α-NPD layer was directly probed and gave a support that only part of the dipoles in P(VDF–TrFE) was polarized. We proposed that the formation of an amorphous insulating layer between amorphous α-NPD layer and partially crystallized P(VDF–TrFE) layer markedly decreased the voltage directly applied on the P(VDF–TrFE) film and caused a reduced polarization. Our findings here will be helpful in analyzing the carrier behavior in organic electronic devices using ferroelectric layers.