Advanced materials and technologies | 2019
Vertically Aligned Piezoelectric Perovskite Nanowire Array on Flexible Conducting Substrate for Energy Harvesting Applications
Abstract
DOI: 10.1002/admt.201900228 a nonpiezoelectric polydimethylsiloxane (PDMS) elastomer. Among 1D piezoelectric nanomaterials, vertically well-aligned NW arrays on a conducting substrate are more suitable for achieving high-output PEHs due to their beneficial morphology compared to lateral NWs on substrates and randomly distri buted NWs inside an elastomer. To verify their applicability in energy harvesting device, many researchers have examined the energy conversion efficiencies of individual 1D NWs taken from ZnO,[2,17] ZnS,[18] CdSe,[19] and GaN[20] NW arrays. They also used NW arrays to demonstrate PEHs that can harvest electric energy source from mechanical deformations and demonstrated the operation of commercial electronic devices by the generated electricity. As of today, the perovskite-structured piezoelectric 1D nanostructures [such as BaTiO3, PZT,[24] and (K, Na) NbO3] have been used to realize energy generation under external pressure. Although previous studies have revealed that perovskite-structured piezoelectric 1D NW arrays can be used for flexible PEHs, they only focused on energy generation under pushing motions and comparatively little work has been done on characterization under bending. Moreover, a theoretical simu lation of operation of NW arrays-based flexible PEH during bending deformation has not yet been well established. This work reports on the use of lead-free biocompatible BaTiO3 NW arrays in the fabrication and investigation of a flexi ble PEH on a thin conducting substrate. Perovskitestructured piezoelectric 1D BaTiO3 NW arrays were vertically grown onto flexible Ti substrates by a facile low-temperature hydrothermal synthesis and were sandwiched between two electrodes by another Ti substrate on top. On repeated bending by a customized bending machine, the BaTiO3 NW arrays-based flexible PEH (activation area of 1.5 cm × 1.5 cm) encapsulated inside a PDMS polymer produced a maximum open-circuit voltage of ≈15 V, a maximum short-circuit current of ≈400 nA, and an effective power of ≈0.27 μW; these values were created for a maximum horizontal displacement of 5 mm from an original 2 cm long sample at a deformation rate of 15 cm s−1. Under an external pressure of 49.57 N introduced by means of a pushing unit, the maximum output voltage and current pulse of the energy harvester were ≈20 V and ≈60 nA, respectively. In addition, to verify the effective piezoelectric potential generation Energy conversion based on vertically aligned piezoelectric nanowire (NW) arrays is of great interest because of their unusual properties originating from large surface area/high aspect ratio and excellent piezoelectric properties. Here, perovskite-structured piezoelectric BaTiO3 NW arrays are vertically grown onto the flexible Ti substrates by a two-step hydrothermal reaction to realize an aligned 1D nanostructures-based flexible energy harvester. The BaTiO3 NW array-based flexible piezoelectric energy harvester (PEH) successfully converts a maximum open-circuit voltage of ≈15 V, a maximum short-circuit current of ≈400 nA, and an effective power of ≈0.27 μW during repeated bending deformations. Under pressing with an external force of 49.57 N, the harvested output signals of the vertically aligned NW arraysbased PEH are ≈20 V and ≈60 nA. Finite element analysis with multiphysics simulation supports the hypothesis of effective potential generation by the NW arrays-based flexible PEH. These results can aid in the further development of high-output 1D nanostructures-based flexible PEHs.