Epitaxy Enhancement of Piezoelectric Properties in P(VDF‐TrFE) Copolymer Films and Applications in Sensing and Energy Harvesting

Abstract

With the rapid development of science and technology, the giant breakthrough of environmentally friendly, efficient, and portable energy sources promotes rapid economic development and great progress in society. Over the past decades, various wearable electronic devices and portable flexible integrated devices have appeared in people's daily lives. These devices play an important role especially in fields of internet of things (IOT) and healthcare, including motion sensing, human health protection, and environmental monitoring. Usually external batteries are used to power these devices. This brings following disadvantages: first, the discarded battery causes pollution to environment; second, with the utilization of more and more sensors, it becomes a mission impossible to replace or recharge those used batteries; third, the presence of external batteries limits the portability of small-scale devices and also affects the biocompatibility between wearable devices and human body. Fortunately, in IOT and healthcare fields most of devices to be powered by batteries are usually of low energy consumption. [1] There exist many energy sources in environment waiting to be converted into electric energy to drive these devices. These sources include at least solar, thermal, and mechanical energies. The concept of nanogenerators was first proposed by using piezoelectric ZnO nanowire arrays to convert nanoscale mechanical energy into electrical energy. After that, piezoelectric, pyroelectric, triboelectric, and hybrid nanogenerators were proposed to convert one-source or even multisource energies into electric energy. Many inorganic and organic photoelectric materials were developed and even commercialized as solar cells, [2] while thermoelectric [3] and pyroelectric [4] effects were both utilized for thermal energy harvesting. Furthermore, mechanical energies widely spread in, such as, human walking, wind, ocean waves, vehicle vibration, and even sound wave. Mechanical energies can be harvested generally based on piezoelectric effect from inorganic and organic materials [5] and piezoelectrets, [6-8] With the rapid development of wearable and flexible electronics, energy harvesting from the environment has attracted much attention. As one representative piezoelectric polymer, poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] is an expected candidate for mechanical energy harvesting and self-powered mechanical sensors due to its flexibility and moderate piezoelectricity. However, low crystallinity and electroactivity limit its electric performance. Controllable modulation of microstructure and crystallization is one feasible measure to enhance piezoelectric property. Here the piezoelectric properties of epitaxial P(VDF-TrFE) films which are fabricated via removable polytetrafluoroethylene template method are reported. Piezoelectric measurement between 50 and 800 Hz presents an averaged d 33 coefficient of −40.7 pC N −1 for epitaxial film, ≈61% enhancement to that of non-epitaxial one. Transverse piezoelectric experiment...

High-Performance Piezoelectric Nanogenerator Based on Low-Entropy Structured Nanofibers for a Multi-Mode Energy Harvesting and Self-Powered Ultraviolet Photodetector

“…The following equation can be used to determine the bending strain ε imposed on the film. : where h sub is the thicknesses of the substrate and h P is the thicknesses of the P­(VDF-TrFE) film. R can be estimated by matching an inscribed circle to the arch’s apex, as illustrated in Figure b.…”

Thermal Release Transfer of Organic Semiconducting Film for High-Performance Flexible Organic Electronics

“…In Figure a–c, optical images of a series of bending moments are shown. Strain (ε) can be determined by − where h PET (150 μm) is PET’s thickness, R is bending radius, and h i represents each film’s thickness that is deposited on the PET substrate, including PMMA, DPP-DTT, and electrode layers. Since h i is far smaller than h PET , strain is mainly determined by PET’s thickness.…”

“…Since h i is far smaller than h PET , strain is mainly determined by PET’s thickness. R can be estimated by fitting an inscribed circle to the apex of the arch of the bended PET substrate. , Note that here bending operation of the flexible device was performed by fixing the device on a linear motor whose movement results in the deformation of the device. This means that the motor can always provide large enough stress to deform the device to preset bending radius.…”

Microstructure Dependence of Output Performance in Flexible PVDF Piezoelectric Nanogenerators

“…Therefore, the β phase content in the PVDF is of primary importance for piezoelectric-based applications. In this case, a wide range of additional processes, including high electric field poling [ 12 ], mechanical stretching along one- or two-directions [ 13 ], epitaxy process [ 14 ], electrospinning [ 9 ] and doping with organic and inorganic materials [ 15 , 16 ]. Comparing these processing methods, electrospinning is considered to be one of the easiest and simplest techniques used to increase the β phase content [ 17 , 18 ].…”