Flexoelectricity-enhanced photovoltaic effect in Flexible LiNbO3 nanorod array/PVDF nanocomposites

Abstract

Recently, flexoelectricity-enhanced photovoltaic effect has gained significant scientific attention. In this investigation, we successfully fabricated vertically aligned LiNbO3 nanorod (LN-NR) arrays and mixed them with a PVDF (polyvinylidene difluoride)) solution to produce LN-NR/PVDF nanocomposites. The flexoelectric coefficient measurement results indicate that the LN-NR/PVDF-91 composite (91% LiNbO3) nanocomposite have the largest flexoelectric coefficient μ133 of 4.95 × 10-8 C/m, which is approximately 9-fold of the pristine PVDF film. The light polarization dependence of the photovoltaic current measurement on a LN-NR/PVDF-91 nanocomposite demonstrated that the increasing of photovoltaic (PV) current arises from the flexoelectric effect. Furthermore, the photovoltaic current (Ipv) of the LN-NR/PVDF composites was measured at various nanomaterials. It was revealed that the Ipv of the flat LN-NR/PVDF-67 (0.65 μA/cm2) nanocomposite increased by13.8-fold compared with that of the LN-nanoparticles/PVDF-67 nanocomposites (43.8 nA/cm2). Next, the photovoltaic current (Ipv) of the LN-NR/PVDF composites was measured at various curvatures. The data indicate that at a downward bending curvature of 20 m-1, the Ipv of the LN-NR/PVDF-91 composites increases by 88% to 1.88 μA cm-2 than that of the composite in the flat condition. In contrast, the Ipv of LN-nanosheet/PVDF-67 nanocomposites (71.3 nA/cm2) only increased by 21.21% to 86.3 nA/cm2 at a curvature of 20 m-1 compared with that of the flat state of the LN-nanosheet/PVDF-67. This demonstrated that the shape of LN nanomaterials can strongly influence the photovoltaic current of LN/PVDF nanocomposites, which mainly due to the increase of the flexoelectricity of aligned LN nanoparticles/PVDF nanocomposites. The DFT (density function theory) calculation result indicates that the bending process can generate piezoelectric coefficient e35 of 0.038 C m-2 at a curvature of 20 m-1. Therefore, LN-nanorods/PVDF nanocomposite shows great potential application prospects on non-destructive readout of ferroelectric memory devices.