Performance Optimization of Vertical Nanowire‐based Piezoelectric Nanogenerators

Abstract

The integrated nanogenerator (NG) based on vertical nanowire (NW) arrays is one of the dominant designs developed to harvest mechanical energy using piezoelectric nanostructures. Finite element method (FEM) simulations of such a NG are developed using ZnO NWs in compression mode to evaluate its performances in term of piezoelectric potential generated, capacitance, induced mechanical energy, output electrical energy, and effi ciency. This evaluation is essential to correctly understand NG operation. Three main issues are highlighted. The mechanical and electrical structures of the NG as an integrated system are optimized, and strategies for concentrating the mechanical strain fi eld in the NWs and increasing the force sensitivity are developed. In addition, the infl uence of NWs length and diameter on NG performances is investigated. The optimization results in a piezoelectric nano composite material where global performances are improved by mean of long and thin NWs.

Unveiling the Influence of Surface Fermi Level Pinning on the Piezoelectric Response of Semiconducting Nanowires

“…There remain many such contradictions between experimental results and the present theoretical understanding of ZnO NW-based devices when realistic doping levels are considered. Chief among them are (1) decent and length-dependent performance of ZnO NWs, [18] while anticipations based on analytical and computational study showed that the output of NWs under compression were reduced to a few millivolts and presenting length-independent performance due to the screening effect; [19,20] (2) enhanced piezoelectric coefficients, [21] which were measured for ZnO NWs with diameter beyond the size effects anticipated by ab initio method; [22] and (3) dissymmetric piezoelectric response of bent nanogenerators (NGs) under tensile and compressive strain. [23] Relatively high potentials (>0.2 V) can be repeatedly obtained from NGs integrating long and large ZnO NWs [24][25][26][27] with presumably nonintentional doping.…”

Theoretical study of output of piezoelectric nanogenerator based on composite of PZT nanowires and polymers

“…The capacitance increases along with the increase of the length of the PZT nanowire from 2.0 mm to 4.0 mm. As the length of PZT nanowire increases, the PZT proportion in the composite increases, which results in the increase of the dielectric constant of the composite, and further leads to a higher capacitance of the device under the fixed thickness [21].…”

“…(1). In addition, decreasing the distance between nanowire tip and the top electrode also contributes to the increase of the output voltage of the device because of the decrease of the electric potential transmission which is induced by the 3D dielectric losses [21].…”

“…The PZT nanowires were well oriented in polymer and their orientations are perpendicular to the electrodes. The device could work in compressive mode [21,22] and bending mode [23,24]. In this paper, the device is evaluated by compressive mode.…”

FEM modeling of vertically integrated nanogenerators in compression and flexion modes

“…The situation is very different for the device working in compression mode, previous work has shown that VING can sustain as high as 1 MPa compressive pressure [8].…”