Infrared-driven poly(vinylidene difluoride)/tungsten oxide pyroelectric generator for non-contact energy harvesting

Piezoelectric Nanogenerators Based on Electrospun PVDF-Coated Mats Composed of Multilayer Polymer-Coated BaTiO3 Nanowires

“…Therefore, the net dipole moment of the β-phase is higher than that of the α-phase, which can produce more power output when subjected to an external load. This is the reason more β phase is beneficial to improve the piezoelectric performance of PVDF. − Figure k shows the XRD patterns of electrospinning nanofibers, investigating the crystal structure of PVDF. One can see that all nanofibers have a distinct crystal peak at 20.6°, corresponding to the overlapping characteristic reflections of the (110) plane and the (200) plane of β-phase PVDF.…”

Gravure Printing for PVDF Thin-Film Pyroelectric Device Manufacture

“…Corona treatment consists in producing a high-frequency electrical discharge able to break the surface molecular bonds of the sub-strate, creating free radicals able to form new surface functional groups [105]. Recently, it has been reported that, by depositing the PVDF from solution onto a hydrophilic substrate, it is possible to obtain self-polarization of the dipoles orthogonally to the substrate, through substrate-PVDF interaction via hydrogen bonds [51]. Since the corona discharge is performed in the air, the free radicals that superficially form on the substrate can interact and combine with oxygen and water atoms, resulting in hydrophilic polar functions [103,104].…”

“…For this purpose, due to its ability to couple very high-throughput and high resolution over a large area, the gravure printing method, widely used in industry, was chosen among different printing techniques because of its great potential in the manufacture of high quality material layers and devices [49][50][51][52]. Among available lead-free pyroelectric materials, polyvinylidene fluoride (PVDF) was selected, as it is potentially better suited for the testing purpose, having the typical advantages of polymers, such as low-temperature processability, low-cost and flexibility [2,29].…”

“…Among these, γ, and even more so, β polar phases are mostly recognized for providing a pyroelectric response [2,8,54,[56][57][58][59][60], but they are thermodynamically less stable than the non-polar α phase and difficult to obtain [58,59,61]. Moreover, to achieve pyroelectric operation in PVDF films, a macroscopic polarization process must be performed to obtain the alignment of polarized covalent bonds in the polar phases [2,8,51]. This process, termed "poling", is typically carried out by mechanical stretching at temperatures of 80-140 • C using a prolonged electric field of at least 100 kV•mm −1 at temperatures of 80-165 • C, or by electrospinning [8,51,62].…”

“…Moreover, to achieve pyroelectric operation in PVDF films, a macroscopic polarization process must be performed to obtain the alignment of polarized covalent bonds in the polar phases [2,8,51]. This process, termed "poling", is typically carried out by mechanical stretching at temperatures of 80-140 • C using a prolonged electric field of at least 100 kV•mm −1 at temperatures of 80-165 • C, or by electrospinning [8,51,62]. Although mechanical stretching is considered the preferred process in the industrial production of pyroelectric films [63], it is not compatible with direct film deposition on substrates [64].…”