Performance Of Piezoelectric Nanogenerators Research Articles

Enhanced Piezoelectric Energy Harvester by Employing Freestanding Single‐Crystal BaTiO3 Films in PVDF‐TrFE Based Composites

AbstractAdvancements in wearable electronics and Internet of Things (IoT) sensors have catalyzed the need for effective micro‐energy harvesting. Piezoelectric nanogenerators (PENGs) are ideal due to their high conversion efficiency and durability. However, the contrast between the high piezoelectric coefficients of brittle inorganic ceramics and the lower coefficients of superior flexibility and biocompatibility of organic polymers poses a significant challenge. This work introduces a novel multilayer composite PENG, integrating a single‐crystal BaTiO3 (BTO) film between poly(vinylidene fluoride‐co‐trifluoroethylene) (PVDF‐TrFE) layers. The PVDF‐TrFE/BTO/PVDF‐TrFE PENGs demonstrate substantially improved energy harvesting performance, with outputs reaching up to 15.1 V, 2.39 µA, and power density of 17.33 µW cm−2 during bending deformation. This power density represents a significant increase compared to pure PVDF‐TrFE and nanoparticle BTO‐doped PVDF‐TrFE PENGs. Durability tests show consistent performance, with a stable ∼15.0 V output across 2000 bending cycles. Additionally, when attached to the human body, these PENGs efficiently convert body motions into electrical responses. This work demonstrates a significant enhancement in the performance of PENGs using sandwich‐structured composite of PVDF‐TrFE and freestanding single‐crystal BTO films, showing its potential to address the power requirements of wearable and flexible electronic devices.

Self-adhesive electrode applied to ZnO nanorod-based piezoelectric nanogenerators

ZnO nanorod-based piezoelectric devices have gained wide attention in energy harvesting systems as they can be processed at low temperatures onto flexible plastic substrates, giving a good potential for low cost. However, the vacuum-evaporated, precious metal contacts remain a high-cost element of the devices. This paper discusses the use of transparent conductive adhesives (TCAs) as an alternative top contact that is free from both vacuum-evaporation and precious metals. TCA films of various thicknesses were tape-cast onto nickel microgrid on PET substrates and adhered using low-pressure cold-lamination to bond the adhesive component of the TCA to piezoelectric generators with the final device structure of PET/ITO/ZnO-seed/ZnO-nanorods/CuSCN/PEDOT:PSS/TCA. The piezoelectric performances of the devices were compared by measuring output voltage in open-circuit and maximum power output across a range of resistive loads. The voltage output was observed to rise with increasing TCA thickness, reaching a maximum value of 0.72 V generated with 110 μm of TCA as top contact. However, the higher resistance due to increased TCA thickness led to decreased power output; a maximum calculated power of 0.25 μW was obtained from the device with the thinnest TCA layer of 22 μm. Finally, the performance of piezoelectric nanogenerators with TCA contacts were compared to a control device with an evaporated gold contact.

Effects of the aspect ratio of ZnO nanorods on the performance of piezoelectric nanogenerators

Abstract This paper presents an investigation on the performance of ZnO nanorod (ZNR)-based piezoelectric nanogenerators (PENGs). ZNRs on the ZnO seed layer coated double-sided flexible polyethylene terephthalate (PET) at different molar concentrations (0.01, 0.05 and 0.1 M) were synthesized by controlling the aspect ratio (length/diameter) of ZNRs, that are closely related to the piezoelectric output potential voltage using a simple hydrothermal method. ZNR PENGs were fabricated with an opposite electrode of gold-coated PET (Au/PET), which was placed on both the top and bottom of the ZNR-coated double-sided PET. X-ray diffraction and field emission scanning electron microscopy images revealed that as the molar concentration increased, the orientation of the as-grown ZNRs became non-uniformly distributed along the c-axis and also along with the decreased aspect ratio. At a low molar concentration (0.01 M), the ZNR PENGs exhibited a relatively high output potential voltage (∼4.48 V) under an external pressing mass (500 g). The ZNR samples grown at 0.05 and 0.1 M exhibited a lower piezoelectric voltage 2.48 and 1.84 V, respectively. These results confirmed that ZNR PENGs with a small diameter, long length (i.e. high aspect ratio) and good alignment tend to be bent more easily for the efficient generation of the piezoelectric potential.

Effect of diameter and height of electrochemically-deposited ZnO nanorod arrays on the performance of piezoelectric nanogenerators

We investigated the performance of zinc oxide (ZnO) nanorod arrays (NRAs)-based piezoelectric nanogenerators (NGs) by controlling their diameter and height which are closely related to piezoelectric output current. The ZnO NRAs as a nanostructured piezoelectric material were synthesized on flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) (i.e., ITO/PET) substrates by a facile electrochemical deposition (ED) method. As the zinc nitrate concentration and growth time increased, the diameter and height of ZnO NRAs also increased. Based on the ZnO NRAs on ITO/PET, piezoelectric NGs were fabricated with an opposite electrode of gold-coated PET film (i.e. Au/PET). At 10 mM of zinc nitrate concentration and 1 h of growth time, the ZnO NRAs exhibited relatively regular and higher output currents, leading to an estimated average value of ∼10.4 nA/cm2 under a low external pushing force of 0.98 N. For the samples at 1 and 100 mM, piezoelectric currents were relatively low (∼4.34 and 1.45–5.21 nA/cm2, respectively). It was found that the ZnO NRAs with high diameter/height uniformity and good alignment tend to be bent more easily for efficiently generating piezoelectric currents. The bending efficiency of ZnO NRAs was also analysed theoretically by calculating the strain distribution of ZnO NRAs-based NGs with different diameters and heights of the nanorods.

Layer‐by‐Layer Controlled Perovskite Nanocomposite Thin Films for Piezoelectric Nanogenerators

Perovskite nanoparticle‐based nanocomposite thin films strictly tailored using unconventional layer‐by‐layer (LbL) assembly in organic media for piezoelectric nanogenerators (NGs) are demonstrated. By employing sub‐20‐nm BaTiO3 nanoparticles stabilized by oleic acid ligands (i.e., OA‐BTONPs) and carboxylic acid (COOH)‐functionalized polymers, such as poly(acrylic acid) (PAA), the resulting OA‐BTONP/PAA nanocomposite multilayers are prepared by exploiting the high affinity between the COOH groups of PAA and the BTONPs. The ferroelectric and piezoelectric performance of the (PAA/OA‐BTONP)n thin films can be precisely controlled by altering the bilayer number, inserted polymer type, and OA‐BTONP size. It is found that the LbL assembly in nonpolar solvent media can effectively increase the quantity of adsorbed OA‐BTONPs, resulting in the dramatic enhancement of electric power output from the piezoelectric NGs. Furthermore, very low leakage currents are detected from the (PAA/OA‐BTONP)n thin films for obtaining highly reliable power‐generating performance of piezoelectric NGs.