Piezoelectric composite film and method for making same

Abstract

The present invention relates to a composite film capable of converting mechanical energy into electrical energy. The film comprises a substrate and piezoelectric nanoparticles configured to form a plurality of pores. The films of the present invention are flexible and highly porous, resulting in a high dielectric constant and beneficial pore-mediated mechanical properties. When used in piezoelectric nanogenerators (PNGs), the films result in increased bulk film strain and reduced film impedance, resulting in highly efficient PNGs with higher output voltages and currents compared to known PNGs. A method for synthesizing the film is also described. The provided method is simple and cost-effective.

Description

Background of the Invention

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit under 35 U.S.C. § 119(e) of provisional patent application SN63 / 102,752, filed June 30, 2020, the contents of which are incorporated herein by reference. FIELD OF THE INVENTION

[0002] In one of its aspects, the present invention relates to a composite film, and more particularly to a piezoelectric composite film configured to include a plurality of pores. The device may be used, for example, as a power source for wireless data communications in personal electronics and for energy harvesting from vibration and biomechanical motion. The device may have applications in structural health monitoring in aircraft, space vehicles, implantable biomedical devices, and the like. 2. Description of the Prior Art

[0003]

[0003] Developing increasingly small structures and high-performance green power sources has become an important area of ​​research to aid in the deployment of self-powered electronics. Piezoelectric nanogenerators (PNGs), which comprise flexible, small structures, have emerged as promising candidates for this purpose. 1 For example, the use of PNG has been reported in self-powered nanoelectromechanical systems (NEMS), electronic / piezotronic devices, implantable medical devices, and remote sensing. 2~8 .

[0004]

[0004] The use of self-powered structural health monitoring (SHM) to monitor the operating condition of aerospace systems has been reported. 9 Such SHM systems are reported to overcome traditional time-poor and costly scheduled maintenance failure modes, thereby enhancing the safety, integrity, and efficiency of aircraft structures. 10 .

[0005]

[0005] Wired sensor networks are now the industry standard for aircraft SHM 11~12 Nevertheless, the implementation of wired networks can be an error-prone method that requires significant manpower and costs. Instead, wireless sensor network systems can effectively eliminate wiring issues. 13 For such wireless systems, a reliable and sustainable power source is often critical. One state-of-the-art technology for powering such wireless systems is piezoelectric energy harvesting devices, which can harvest energy from the surrounding environment. 7、14 .

[0006]

[0006] Energy harvesting techniques, e.g., electromagnetic 18~22 and electrostatic 23~25 Triboelectricity based method 15 and piezoelectric 16~17 Nanogenerators and devices have been investigated for their ability to harvest ambient energy, such as from vibrations, wind, raindrops, and ocean waves. Triboelectric nanogenerators (TENGs) have been reported to have high energy conversion efficiency, high output voltage, and flexible material options, as well as being lightweight and low cost. 26~38 However, TENGs may suffer from a lack of durability and compactness, which may limit their SHM applications, especially in aircraft. On the other hand, piezoelectric nanogenerators (PNGs) have been reported to exhibit mechanical robustness, environmental compatibility, and sensitivity, suggesting their potential for SHM applications. 39~42 .

[0007] Many materials have been reported for the fabrication of PNG, such as inorganic lead zirconate titanate (PZT), barium titanate (BaTiO), zinc oxide (ZnO), Na / KNbO, and ZnSnO nanoparticles, which are reported to have large piezoelectric coefficients and high energy conversion efficiencies. 39~43、106~108Organic piezoelectric polymers, such as polyvinylidene fluoride (PVDF) and the copolymer hexafluoropropylene [P(VDF-HFP)] trifluoroethylene (P(VDF-TrFE)), and poly(vinyl acetate) (PVAc), have also attracted more attention due to their high flexibility, biocompatibility, simple material synthesis methods, and the reported existence of an energy-efficient β-phase. 109~113 However, endogenous PVDF-based PNGs generate lower electrical energy output compared to their inorganic counterparts. 114~122 .

[0008]

[0008] Modification of the microstructure of piezoelectric films to enhance strain-dependent piezoelectric polarization has been reported as a mechanism for utilizing energy sources. Strategies such as the introduction of nanowires have been reported. 43~46 ,Aspect ratio tuning,Film porosity modulation via multi-step etching method 25、47~52 , cascading multiple devices 53~56 , and a reduction in the charge shielding effect 57~61 is a structure-driven technique that has been reported to push the limits of piezoelectricity. For example, Su et al. reported that by creating pores in zinc oxide (ZnO) nanowires, the output current of PNG increased by approximately 23 times (27.7 nA) with a 5.4% increase in the porosity percentage. 47 Using random, highly porous (50%) polyvinylidene fluoride (PVDF) structures (by etching), Mao et al. reported PNGs with output voltages and currents of 11.1 V and 9.7 μA, respectively, which are higher than those reported for lithographically-based porous PVDF nanowire arrays. 48、53 reported a cascade-type six-layer rugby ball-shaped PNG structure, which achieved an output performance of 88.62V. PP and increased to 353 μA 55 .

[0009] Although piezoelectricity has been reported to be enhanced by these strategies, optimally integrating suitable mechanical and electrical properties in a single piezoelectric film can be challenging. For example, among piezoelectric materials, single crystals such as lead zirconate titanate (PZT), (1-x)Pb(Mg 1 / 3 Nb 2 / 3 )O3-xPbTiO3(PMN-PT) 62 has a high piezoelectric coefficient (d 33 However, these materials require high-temperature synthesis and can be fragile. Lead-free piezoelectric materials can be more environmentally friendly, but the power performance of such materials is reported to remain moderate. 63 .

[0010]

[0010] It has been reported that dispersing highly piezoelectric nanoparticles (NPs) into flexible polymers to form films improves fabrication scalability, device flexibility, mechanical strength, and electrical output. 64~68 However, such reports require the utilization of NP dispersion promoters to improve the homogeneous dispersion of NPs in the polymer backbone, which may adversely affect device performance. 69~74 Other researchers have reported that by functionalizing the surface of piezoelectric NPs before mixing them with polymers, 75 It has been reported that this problem has been addressed by replacing the NPs with organic-inorganic metal halide perovskites (OMHPs), such as methylammonium lead iodide (MAPbI3) or formamidinium lead halide (FAPbBr3) homogeneously dispersed in a PVDF or polydimethylsiloxane (PDMS) matrix; however, these films may still have issues with brittleness and scalability. 40、41、76、77 .

[0011]

[0011] Despite the progress made to date in the development of piezoelectric films, there remains room for improvement to address the problems and weaknesses of the prior art. Summary of the Invention

[0012] It is an object of the present invention to obviate or mitigate at least one of the above-mentioned disadvantages of the prior art.

[0013] It is another object of the present invention to provide a novel film composite having a piezoelectric potential.

[0014]

[0014] Accordingly, in one of its aspects, the present invention provides a film comprising a perovskite and a polymer, wherein the perovskite and polymer are configured to form a plurality of elongated pores.

[0015]

[0015] In another aspect of the present invention, the present invention provides a method for producing a film, the method comprising the steps of: (a) preparing a first solution by adding a polymer to a first solvent; (b) preparing a second solution by adding a perovskite to a second solvent; (c) homogeneously mixing the first solution with the second solution to create a mixture; and (d) maintaining the mixture at a substantially constant temperature to crystallize the polymer and perovskite.

[0016]

[0016] In another aspect of the present invention, the present invention provides a composite film comprising a substrate and a plurality of piezoelectric nanoparticles, wherein the substrate and nanoparticles are configured to form a plurality of pores, and the composite comprises two opposing major surfaces interconnected by the pores.

[0017]

[0017] Thus, the present inventors have developed a composite piezoelectric film comprising a substrate and piezoelectric nanoparticles configured to form a plurality of pores. This film is flexible and highly porous, providing a high dielectric constant and pore-mediated mechanical properties. When used in PNG applications, the film provides increased bulk film strain and reduced film impedance, resulting in highly efficient PNGs with higher output voltages and currents compared to other reported PNGs. The present film, with its enhanced output power capability and large area scalability, is believed to have application as a compact, flexible power source in self-powered micro / nano wireless devices to harvest mechanical energy from a range of environmental vibrations. The present inventors have also developed a simple, low-cost method for preparing the film.

[0018] To the inventors' knowledge, no film has been previously known that possesses this combination of characteristics.

[0019] Other advantages of the present invention will become apparent to those skilled in the art upon review of the present specification.

[0020] Aspects of the present invention will now be described with reference to the accompanying figures, in which, for example, reference numerals represent the various parts, and in which: [Brief explanation of the drawings]

[0021] [Figure 1] Figure 1 shows the characterization of the pure PVDF film: (a) top surface of the pure PVDF (annealed at 75 °C); (b) scanning electron microscopy (SEM) image of the cross section of the pure PVDF film; (c) FTIR spectrum of the PVDF film (wavenumber 510 cm-1 and corresponding absorption at 841 cm-1). [Figure 2]Figure 2 shows the characterization of one embodiment of a film of the present invention, in which the film comprises ZnO-PVDF. (a) Top-view SEM image of PVDF loaded with ZnO nanoparticles (NPs) with diameters of 35–45 nm; (b) Cross-sectional SEM image of PVDF loaded with ZnO NPs. The SEM images show that the nanoparticles are not uniformly dispersed but rather accumulate at different locations in the PVDF film. This creates pores of different sizes after the etching process; (c) Top-view SEM image of a porous PVDF film obtained after etching the ZnO NPs with 37 wt% hydrochloric acid (HCl); (d) Atomic force microscopy (AFM) image of the porous PVDF surface; (e) Measured surface roughness (100 nm) of the porous PVDF. [Figure 3] Figure 3 shows another embodiment of a film of the present invention, in which the film comprises a perovskite polymer. The perovskite polymer film shown comprises FAPbBr2I-PVDF and is incorporated into a piezoelectric nanogenerator (PNG). (a) PNG fabrication method; (b) XRD pattern of a perovskite polymer film of the present invention that is 20 wt% FAPbBr2I@PVDF; (c) FTIR results of a porous PVDF film and a perovskite polymer film of the present invention that is 25 wt% FAPbBr2I@PVDF; (d) Digital photographs of a large area film (approximately 15 cm x 15 cm) and the fabricated PNG. [Figure 4] Figure 4 shows (a) a cross-sectional SEM image of the perovskite polymer film (20 wt % PVDF@FAPbBr2I) in Figure 3 (the inset shows a magnified image of the pores); (b) the corresponding elemental mapping of fluorine in PVDF and (c) lead in the perovskite polymer film; (d) the calculated stress and (e) the piezoelectric potential distribution for similar areas of the pure PVDF film in Figure 1, the 20% porous PVDF film in Figure 2, and the 60% porous perovskite polymer film (porosity induced by 20 wt % FAPbBr2I) in Figure 3. [Figure 5]Figure 5 shows the morphology of the pore structure of the perovskite polymer film in Figure 3. (a) Cross-sectional SEM image of the perovskite polymer film showing regularly distributed pores with lengths of 20–25 μm; (b) Surface topography of the FAPbBr2I@PVDF film from an AFM image showing the pore diameters of approximately 3–5 μm. [Figure 6] Figure 6 shows a schematic diagram of the crystallization process of PVDF and FAPbBr2I nanoparticles in the perovskite polymer film of Figure 3. The y-axis represents the total concentration of PVDF and FAPbBr2I in solution; (b) Schematic evidence showing the interaction between FA+ cations and -CF2- groups. FTIR spectra confirm this interaction by a blue shift of the infrared absorption peak of the C-F bond in the wavenumber range of 1350–1100 cm-1. [Figure 7] Figure 7 shows atomic force microscopy (AFM) images of the perovskite polymer films in Figure 3 with different mass ratios (wt%) of FAPbBr2I precursor solution in 10 wt% PVDF precursor solution: (a) 5 wt%; (b) 10 wt%; (c) 15 wt%; (d) 20 wt%; (e) 25 wt%; (f) 30 wt%; and (g) the grain boundary topology of FaPbBr2I NPs (100 nm). [Figure 8] Figure 8 shows finite element simulations of the pure PVDF film of Figure 1, the porous PVDF film of Figure 2, and the perovskite polymer film of Figure 3 under a compressive pressure of 800 kPa. (a) Finite element simulations of the pure film, the porous PVDF film, and the perovskite polymer film under a compressive pressure of 800 kPa. Mechanical stresses are calculated along (b) the horizontal axes (A–F) and (c) the vertical axis. [Figure 9]Figure 9 shows a graphical characterization of the piezoelectric potential distribution for the perovskite polymer film (20 wt% FAPbBr2I@PVDF) in Figure 3 in the presence of a single pore structure and a pore (8-pore) array structure. The pore shape was optimized from the observation of cross-sectional SEM images of the film. (a) Mechanical stress distribution for the film with a pore array structure (left) and a film with a single pore structure (right). The arrows indicate the amplified stress on the sidewall of each pore. (b) The piezoelectric potential distribution is higher in the film with the presence of many pore structures (left). [Figure 10] Figure 10 shows the energy harvester characterization system. The controller unit is operated by a workstation interface (Fig. 9). The controller unit (VR9500) generates different control signals, which are amplified by a power amplifier (Lab Works Inc.'s PA138) and fed to an electrodynamic shaker (ET-126-1) to control its operation. An accelerometer (3055D3) provides a feedback signal from the shaker to the controller unit so that action can be taken in case of any faults. The shaker is mechanically coupled to a metal hammer to characterize the energy harvesting device. The output from the device is measured and observed on an oscilloscope. [Figure 11] Figure 11 shows the maximum power performance of the perovskite polymer PNG of Figure 3. (a) Output voltage and (b) current of the perovskite polymer PNG at 30 Hz and 2 G acceleration when subjected to a load of 138 grams (g). [Figure 12] Figure 12 shows a schematic diagram of the energy generation mechanism of the perovskite polymer PNG in Figure 3 based on the stress distribution profile. [Figure 13] FIG. 13 shows the variation of (a) the output voltage and (b) the output current of the perovskite polymer PNG of FIG. 3 with different FAPbBr2I mass ratios (0 wt%, 10 wt%, 20 wt%, 30 wt%). [Figure 14]Figure 14 shows the power performance of PNGs. (a) Voc and (b) Isc of PNGs fabricated from pure PVDF (Figure 1), porous PVDF film (Figure 2), and perovskite polymer film (Figure 3). For PGNs containing porous PVDF film and perovskite polymer film, the original mass ratio of particles inside the final film was 20 wt%. (c) Verification of polarity formation of perovskite polymer PNGs by switching test; (d) relative permittivity of PVDF PNGs and perovskite polymer PNGs; KPFM images of (e) porous ZnO-PVDF film and (f) perovskite polymer film. [Figure 15] Figure 15 shows the frequency-dependent output power performance of the perovskite polymer PNG of Figure 3 with an input excitation of 10-50 Hz and 2 G acceleration. The maximum output voltage and current at 30 Hz frequency were 85 V and 30 μA, respectively. The slow decrease in output power at higher frequencies (>30 Hz) corresponds to the decreasing effect of the 138 gram (g) test mass on the PNG. [Figure 16] Figure 16 shows the flexibility test of the perovskite polymer PNG of Figure 3 at 10 Hz and 2 G acceleration when a cyclic bending force is applied from an electrodynamic shaker. The generated (a) output voltage (b) output current, 14 V and 0.3 mA, respectively, represent the performance of the perovskite polymer PNG during bending. [Figure 17] Figure 17 shows the framework for a self-powered integrated wireless electronics node (SIWEN) by using the perovskite polymer PNG of Figure 3 as a power source and sensor simultaneously. [Figure 18] Figure 18 shows the internal structure of the self-powered integrated wireless electronics node (SIWEN): (a) functional block diagram of the SIWEN, (b) internal circuit diagram of the LTC3588-1 module, and (c) structure of the RSL-10 system-on-chip (SoC). [Figure 19]Figure 19 shows the application of the perovskite polymer PNG of Figure 3 for IoT. (a) Measured output power of the perovskite polymer PNG under an applied acceleration of 2 g (30 Hz). The load used was a 138 g metal block; (b) Charging characteristics of the SIWEN's input (1 μF) and output capacitors (220 μF); (c) Digital photograph showing the sensor signal received by a mobile phone; (d) SIWEN being used to detect a car engine state in a parked position (the inset shows the corresponding frequency domain distribution via fast Fourier transform); (e) Charging a commercial capacitor (1 μF) by a single perovskite polymer PNG while excited by a car engine; (f) Corresponding digital photograph of engine vibration detection. [Figure 20] 20 shows the structural design of another embodiment of the film of the present invention, in which the film comprises porous PVDF. The film shown comprises porous PVDF and is integrated into a PNG and a functional wireless sensing circuit. (a) Schematic of the functional elements of the porous PVDF PNG, which is mainly composed of a PNG unit and an integrated circuit unit; (b) Close-up of the original circuit; (c) PNG device as fabricated; (d) Illustration of the entire sensing system in a block diagram. [Figure 21] FIG. 21 shows (a) an as-fabricated large-scale embodiment (approximately 15 cm x 15 cm) of the porous PVDF film of FIG. 20; (b) a cross-sectional scanning electron microscopy (SEM) image of the surface of a pure PVDF film, annealed at 65°C; and (c) a cross-sectional SEM image of ZnO-NPs dispersed in a porous PVDF film. [Figure 22]Figure 22 shows the material characterization of the porous PVDF PNG shown in Figure 20. Scanning electron microscopy (SEM) images of (a) pure PVDF film; (b) distribution analysis of ZnO NPs in the PVDF matrix of the porous PVDF film (inset is the film before etching); (c) top-view SEM of the porous ZnO-PVDF film after etching of ZnO NPs (inset is the real film after etching); (d) surface morphology by AFM; (e) characterization of the crystallinity of the PNG by Fourier transform infrared spectroscopy (FTIR) spectra to confirm β-phase formation. [Figure 23] FIG. 23 shows an atomic force microscopy (AFM) image of the surface of the porous PVDF film of FIG. 20; (b) the measured surface roughness of the porous PVDF film. [Figure 24] FIG. 24 shows a schematic representation of the energy generation mechanism from the porous PVDF PNG of FIG. [Figure 25] Figure 25 shows the measured experimental and simulated electrical output performance of the porous PVDF PNG of Figure 20. (a) Peak-to-peak output voltage at 30 Hz frequency and 2 G acceleration, with the porous PVDF PNG top surface weighted with a standard mass of 138 grams; (b) Peak-to-peak output current at 30 Hz frequency and 2 G acceleration, with the PNG top surface weighted with 138 grams; (c) Stress distribution for a 50 wt% porous PVDF film; (d) Electric potential distribution for a 50 wt% PVDF porous film, with a peak output voltage of 39.8 volts; (e) Short-circuit current polarity switch test to determine piezoelectricity; (f) Stability test of the porous PVDF PNG for 36,000 cycles (30 Hz for 20 minutes). [Figure 26] Figure 26 shows the measured open circuit voltage of films at a frequency of 30 Hz when the ZnO mass fraction increases from 0% (pure PVDF) to 60%, including (a) the preparation of ZnO-PVDF solutions with ZnO mass ratios of 0 to 60 wt% (0 and 50 wt% are not shown here); (b) the prepared solutions of ZnO-PVDF with almost identical thicknesses. [Figure 27]FIG. 27 shows (a) the stress distribution for a pure PVDF film and (b) the potential distribution for a pure PVDF film, with a peak output voltage of 10.9 volts. [Figure 28] Figure 28 shows that (a) the output short-circuit current of the porous PVDF PNG of Figure 20 (50 wt%) in the frequency range 10 Hz to 50 Hz and (b) the open-circuit voltage revealed identical amplitudes with reversed polarity formation, confirming the reliability of the piezoelectric output signal. [Figure 29] Figure 29 shows the demonstration of the high power capability and anticipated applications of the porous PVDF PNG device of Figure 20, which contains 50 wt% porous PVDF film. (a) Comparison of the output voltage of the porous PVDF film over a wide range of frequencies from 10 Hz to 50 Hz; (b) Output voltage measured across various commercially available capacitor values ​​of 1 μF, 2.2 μF, 4.7 μF, 10 μF, 47 μF, and 100 μF charged with a porous PVDF PNG excited at 30 Hz; (c) Measured output peak power and peak power density under load of the porous PVDF PNG at a frequency of 30 Hz; (d) Measured output voltage across the input and output capacitors of the EMM when the porous PVDF PNG is excited by a linear motor shaking at 30 Hz; (e) Practical configuration of a linear shaker, where the device is fixed on top of the shaker and a 138-gram mass is applied on top of the porous PVDF PNG; and (f) Signal transmission via a Bluetooth® device. Detailed Description of the Preferred Embodiments

[0022]

[0021] The present invention also relates to a film comprising a perovskite and a polymer, wherein the perovskite and polymer are configured to form a plurality of elongated pores.

[0023] Preferred embodiments of this film may include any one or a combination of any two or more of any of the following features: The film comprises two opposing major surfaces interconnected by pores; the pores are at least partially aligned perpendicular to the two opposing major surfaces of the film; · When force is applied to the main surface of the film, the pores deform; The pores are approximately 20 μm to 25 μm in length; The pores are about 3 μm to about 5 μm in diameter; · Perovskites contain nanoparticles; · Perovskite is embedded in a polymer; · The film contains perovskite in crystalline form; · Perovskite crystals contain non-centrosymmetric structures; · Perovskites include hybrid halide perovskites; · Perovskites include (HHP)-formamidinium lead bromide iodide (FAPbBr2I); · The film contains the polymer in the crystalline β phase; · the polymer is selected from the group consisting of polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), and polyethyl acrylate (PEA); · Polymers include polyvinylidene fluoride (PVDF); the film comprises a perovskite in a mass ratio of about 10 wt % to about 30 wt %; The film comprises perovskite in a mass ratio of about 20% by weight; The film comprises a polymer in a mass ratio of about 10% by weight to about 15% by weight; the film comprises a polymer in a mass ratio of about 10% by weight; · the film comprises a plurality of dipoles, said dipoles being substantially aligned; The film has a thickness of about 20 μm to about 50 μm; The film has a thickness of about 30 μm; ·The film is formed by a two-step crystallization method; A piezoelectric nanogenerator comprising the claimed film, a first electrode, and a second electrode, wherein the film is in electrical contact with the first electrode and the second electrode; · The claimed piezoelectric nanogenerator, wherein the first electrode comprises a metal or a polymer; · The claimed piezoelectric nanogenerator, wherein the first electrode comprises a metal selected from the group consisting of copper, gold, and aluminum; · The claimed piezoelectric nanogenerator, wherein the first electrode comprises poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS); · The claimed piezoelectric nanogenerator, wherein the second electrode comprises a metal or a polymer; · The claimed piezoelectric nanogenerator, wherein the second electrode comprises a metal selected from the group consisting of copper, gold, and aluminum; · The claimed piezoelectric nanogenerator, wherein the second electrode comprises poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS); · A claimed piezoelectric nanogenerator, wherein the nanogenerator is encapsulated by a substrate; · The claimed piezoelectric nanogenerator, wherein the substrate comprises polyester; · A claimed piezoelectric nanogenerator, wherein the nanogenerator is encapsulated using a thermal lamination method; ·An aircraft structural health monitoring system incorporating the claimed piezoelectric nanogenerator; a self-powered device incorporating the claimed piezoelectric nanogenerator; and A claimed self-powered device, wherein the device is a wearable electronic device, a medical diagnostic device, or an implantable device.

[0024]

[0023] The present invention also relates to a method for producing a film, comprising the steps of: (a) preparing a first solution by adding a polymer to a first solvent; (b) preparing a second solution by adding a perovskite to a second solvent; (c) homogeneously mixing the first solution with the second solution to create a mixture; and (d) maintaining the mixture at a substantially constant temperature to crystallize the polymer and perovskite.

[0025] Preferred aspects of the method may include any one or a combination of any two or more of any of the following features: The mixture is then cast and annealed to form a film; The film is then poled using a high voltage electric poling process; · Polymers crystallize before perovskites; The first solution comprises a polymer in a mass ratio of about 10% by weight to about 15% by weight; The first solution comprises a polymer in a mass ratio of about 10% by weight; the second solution contains the perovskite in a mass ratio of about 10 wt % to about 30 wt %; the second solution contains perovskite in a mass ratio of about 20% by weight; The first solvent is N,N-dimethylformamide; The second solvent is N,N-dimethylformamide; The mixture is maintained at a temperature of about 60°C; · the polymer is selected from the group consisting of polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), and polyethyl acrylate (PEA); Polymers include PVDF; · Perovskites include hybrid halide perovskites; · Perovskites include FAPbBr2I; a film produced by the claimed method; and A piezoelectric nanogenerator comprising a film produced by the claimed method.

[0026]

[0025] The present invention also relates to a composite film comprising a substrate and a plurality of piezoelectric nanoparticles, wherein the substrate and nanoparticles are configured to form a plurality of pores, and the composite comprises two opposing major surfaces interconnected by the pores.

[0027] Preferred embodiments of the composite film may include any one or a combination of any two or more of any of the following features: · The substrate is a polymer; The polymer is in the crystalline β phase; The polymer is PVDF; · Piezoelectric nanoparticles include perovskites; · Perovskites include hybrid halide perovskites; · Perovskites include (HHP)-formamidinium lead bromide iodide (FAPbBr2I); ·Pores are elongated; the pores are aligned at least partially perpendicular to the two opposing major surfaces of the composite film; · Piezoelectric nanoparticles include zinc oxide (ZnO) nanoparticles; ·ZnO nanoparticles are randomly dispersed throughout the composite film; The composite film contains ZnO nanoparticles in a mass ratio of approximately 10% to approximately 50% by weight. The composite film contains ZnO nanoparticles at a mass ratio of approximately 50% by weight. ·ZnO nanoparticles have a diameter of about 25 nm to about 55 nm; ·ZnO nanoparticles have a diameter of about 35 nm to about 45 nm; ·ZnO nanoparticles are dispersed throughout the composite film by ultrasonic treatment; The piezoelectric nanoparticles are removed from the composite film; and A piezoelectric nanogenerator comprising the claimed composite film, a first electrode, and a second electrode, wherein the film is in electrical contact with the first electrode and the second electrode.

[0028] Preferred embodiments of the present invention are described with reference to the following illustrative information, which should not be used to limit or interpret the present invention. A. Perovskite polymer composite film 1. Experimental Method 1.1 Film composition a. Pure PVDF film Pure or "solid" PVDF films were prepared. To prepare the PVDF solution, PVDF was purchased in powder form (Sigma Aldrich) and dissolved in N,N-dimethylformamide solvent (N,N-DMF; ≥99%, Sigma Aldrich) (10 wt %) by stirring at 40°C for 12 hours. The temperature was maintained at 40°C to prevent aggregation and achieve better dissolution. To prepare the PVDF film, the solution was drop-cast onto a standard glass wafer placed on a flat hotplate. The sides of the glass substrate were covered with polyamide tape to prevent outward flow of the solution. Before the first annealing step, the solution was kept at ambient conditions for 30 minutes for degassing. To form the spontaneously occurring electroactive β-phase in PVDF, the curing temperature was adjusted to 80°C for 1 hour, and then a thin film (approximately 40-50 μm) was peeled off from the glass substrate. The formation of the β-phase in PVDF was confirmed by FTIR spectroscopy (Figure 1c), and the surface morphology was investigated using scanning electron microscopy (SEM) (Figures 1a-b). Finally, high-voltage electrical polarization (50-120 V / μm) was performed for 2-4 hours to align the electric dipoles. For the high-voltage polarization, two gold-coated copper electrodes were prepared via electroplating. To minimize the negative effects of ambient moisture and dust particles, the electrical polarization was performed in a vacuum box. To produce PNG, the film was placed between two copper tapes and then thermally laminated between two polyester substrates. b. Porous PVDF film

[0029] Porous PVDF films were prepared. PVDF powder was dissolved in N,N-DMF by stirring the solution at 40 °C for 12 h. To create different pore sizes, ZnO nanoparticles (NPs) (35–45 nm, US Research Nanomaterials, Inc.) were dispersed in the PVDF solution and stirred at 40 °C for 24 h. The mass ratio between PVDF and ZnO NPs (20 wt%) was adjusted to create different pore sizes inside the PVDF. To achieve a homogeneously mixed ZnO-PVDF composite solution, the solution was further treated in an ultrasonic bath for 1 h. The homogeneous solution was drop-cast onto a glass substrate and degassed for 30 min. The solution was cured in a vacuum oven at 75 °C for 30 min. The ZnO-PVDF film was then peeled off from the glass substrate (see Figures 2a–b for surface and cross-sectional morphology). To obtain porosity inside the PVDF, the ZnO-PVDF film was immersed in a 37 wt% HCl solution for 4 h, and one-step etching of the ZnO NPs was performed in an ultrasonic bath. The film was then rinsed with DI water and dried at 60 °C for 3 h in a nitrogen-filled oven (see Figure 2c-e for surface morphology). Finally, a high-voltage electrical poling treatment (50-120 V / μm) was performed for 2-4 h to align the dipoles. To produce PNGs, the film was placed between two copper tapes and thermally laminated between two polyester substrates. c. Perovskite polymer film

[0030] 3 shows an embodiment of a composite film of the present invention, in which the film comprises perovskite nanoparticles and a polymer substrate. The perovskite can comprise any perovskite comprising crystals with a non-centrosymmetric structure, preferably comprising (HHP)-formamidinium lead bromide iodide (FAPbBr2I). The substrate is electrically insulating and can comprise a flexible polymer, such as polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), or polyethyl acrylate (PEA), preferably comprising PVDF.

[0029]

[0031] The solvent used for the precursor solution must be capable of dissolving the perovskite and the polymer. Different solvents can be used for the perovskite precursor solution and the polymer precursor solution, as long as each solvent can dissolve both the perovskite and the polymer. For example, the solvent can be N,N-DMF, dimethyl sulfoxide (DMSO), or tetrahydrofuran (THF), preferably N,N-DMF for both the perovskite precursor and the polymer precursor solutions.

[0030]

[0032] To prepare perovskite polymer films, a perovskite precursor solution was prepared by dissolving formamidinium iodide (FAI; ≥99%, Sigma-Aldrich) and lead(II) bromide (PbBr; ≥98%; Sigma-Aldrich) in an equal molar ratio (0.5:0.5) in N,N-DMF (≥99%; Sigma-Aldrich), followed by stirring at 60 °C for 12 h. A polymer precursor solution was prepared by dissolving PVDF in N,N-DMF with constant stirring at 50 °C for 24 h. The final concentrations of FAIbBrI and PVDF in N,N-DMF were 20 wt% and 10 wt%, respectively.

[0031]

[0033] Next, a perovskite-polymer composite solution was prepared by homogeneously mixing the perovskite precursor solution (20 wt % FAPbBr2I) with the polymer precursor solution (10 wt % PVDF). To optimize the concentration, 10 wt %, 20 wt %, and 30 wt % composite solutions were synthesized. The mixed solution was drop-cast onto a glass substrate and stored for approximately 1 hour for degassing. This was immediately followed by annealing at 120 °C, resulting in a crystalline film after 2–3 hours. To align dipoles within the perovskite polymer film, a high-voltage electric polarization process was completed by applying an electric field of 50–120 V / μm for 2–3 hours. For the high-voltage polarization process, two gold-coated copper electrodes were prepared via electroplating. To minimize the negative effects of ambient moisture and dust particles, the electric polarization process was performed in a vacuum box. 1.2 Fabrication of perovskite polymer film piezoelectric nanogenerator (P-PNG)

[0034] To prepare the perovskite polymer film PNG, the perovskite polymer film was sandwiched between two electrodes. The electrodes can be any suitable metal or polymer with good electrical conductivity and optimal work function, preferably copper, gold, aluminum, or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). For the perovskite polymer PNG of the present invention, a copper electrode was used.

[0032]

[0035] Wire connections were made to the top and bottom electrodes with 100 μm insulated copper conductors. The perovskite polymer film and electrodes were then compressed via thermal lamination to eliminate voids and achieve uniform adhesion between the copper electrode and the perovskite polymer film. The resulting structure was polyester / copper / FAPbBr2I-PVDF / copper / polyester PNG (see Figure 3a). 1.3 Characterization and Measurement

[0036] To investigate the crystallinity of the hybrid halides in the ferroelectric PVDF framework, X-ray diffraction (XRD) analysis was performed. A Bruker D8 DISCOVER with a Cu KR irradiation source (λ = 1.54 Å) was used to scan optimized thin film samples (25 wt% FAPbBr2I-PVDF) over an angle range of 0–70 degrees.

[0033]

[0037] Fourier transform infrared spectroscopy (Nicolet iS50) was used to measure the chromatographic peaks from 400 to 1000 cm -1 The formation of ferroelectric β-phase inside the porous PVDF film and the perovskite polymer film was confirmed by measuring characteristic absorbance peaks in the wavenumber range of 1000 Hz.

[0034]

[0038] The dielectric properties of the samples (CV characteristics) were measured using a Keithley-4200 semiconductor parameter analyzer. Surface morphology was obtained using a JSM-7200F field-emission scanning electron microscopy (JSM-7200F) tool, and the nanoparticle distribution inside the PVDF was mapped by energy-dispersive X-ray analysis in a cleanroom environment (Class-100). All atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) images were recorded using a JPK Nanowizard II configured in intermittent contact mode (scan rate 0.3 Hz). For KPFM, an imaging cantilever (spring constant 42 N / m) with a platinum-coated tip (radius <20 nm) was used to probe the milled sample. A phase-locked loop maintained constant tip-sample interaction, and the internal reference for the lock-in amplifier was an AC voltage (3 kHz) applied to the sample surface.

[0035]

[0039] To measure the electrical output performance of the perovskite polymer PNG, an electrodynamic shaker (Labworks Inc.) was used to control the power amplifier and controller. A digital oscilloscope (Tektronix 2004C) and a low-noise current preamplifier (Model-SR 570, Stanford Research System Inc.) were used to measure the electrical signal output from the PNG. 2. Results and Discussion 2.1 P-PNG device structure and operation mechanism

[0040] Figure 3a shows a schematic diagram of one embodiment of the perovskite polymer film of the present invention, in which the perovskite polymer film is used to fabricate a PNG. As shown, in the final device fabrication process, the perovskite polymer film is sandwiched between two copper electrodes and encapsulated between polyester substrates via thermal lamination.

[0036]

[0041] To clarify the formation of perovskite crystals inside the PVDF, XRD scans were performed over a wide range (diffraction angles 2θ ranging from 10 to 50 degrees). Figure 3b shows the main diffraction peaks at diffraction angles (2θ) of 14.64, 29.43, 33, 42.12, and 44.39, which can be assigned to the (100), (220), (222), (224), and (300) crystal planes of the cubic perovskite structure, respectively.

[0037]

[0042] Semicrystalline PVDF polymer has four distinct phases (α, β, γ, and δ), with the β phase being the only phase that possesses the highest spontaneous polarity. The presence of the β phase can be confirmed by Fourier transform infrared (FTIR) spectroscopy. The FTIR spectrum shown in Figure 3c shows that the β phase is significantly higher than the β phase in the porous PVDF film compared to the β phase. 78~79 The perovskite polymer film of the present invention has a wavenumber of about 475 cm -1 Higher intensity at 840cm -1 Without wishing to be bound by any particular theory or mechanism of action, this result demonstrates that the FA of FAPbBr2I + This can be attributed to the improved β-phase crystallization of PVDF due to the existence of dipole interactions between cations and the anionic fluorine (-CF2-) groups of PVDF. 80~81 .

[0038]

[0043] The piezoelectric coefficient (D3) of the films of the present invention can be expressed as follows: D3=α1L E φd1+α2(1-φ)d2(1) where α1 and α2 are the poling rates, d1 and d2 are the piezoelectric coefficients of the different materials in the film, respectively, and L E is the local field coefficient and φ is the mass fraction). Assuming that the organic and inorganic phases are fully polarized, i.e., α1 = α2 = 1, and φ = 0.2, we can predict the piezoelectric coefficient D3. The local electric field (L E =3ε / (2ε+ε c )) is a FAPbBr2I nanoparticle (ε c) and the relative dielectric constant of the film (ε). ε c It has been reported that L can reach 1000, which is much larger than ε. E is predicted to be approximately 0.1 to 0.3 82 The piezoelectric coefficients of the PVDF and FAPbBr2I phases were determined to be opposite. Given that d1 is approximately 25 pm / V and d2 is approximately -29 pm / V, the calculated approximate D3 is -23 pm / V. 41 Furthermore, other factors, such as nanoparticle distribution and film shape, may also affect the piezoelectricity of the films of the present invention. The scalability of the perovskite polymer film of the present invention (approximately 15 cm × 15 cm) and the fabricated flexible perovskite polymer PNG device is shown in Figure 3d. It was found that a small force applied to the PNG by the touch of a human hand was capable of generating enough energy to drive an LED (data not shown).

[0039]

[0044] As shown in the scanning electron microscopy (SEM) image in Figure 4a, a series of nearly periodic vertical pores were observed from the cross section of the perovskite polymer film of the present invention. In contrast to the solid and porous PVDF films (Figures 1 and 2), a self-assembled, highly porous structure was found in the perovskite polymer film.

[0040]

[0045] The pores may be of any length, preferably about 15 μm to about 35 μm, more preferably about 20 μm to about 25 μm. The pore diameter may be any size, preferably about 2 μm to about 8 μm, more preferably about 3 μm to about 5 μm.

[0041]

[0046] As shown in Figure 5, the pores in the perovskite polymer film of the present invention were approximately 20-25 μm in length (as shown in the SEM image in Figure 5a) and approximately 3-5 μm in diameter (as shown in the atomic force microscopy (AFM) image in Figure 5b).

[0042]

[0047] During the crystallization process, phase separation plays a role in the formation of the porous structure of the perovskite polymer film of the present invention. As a result, the crystallization process can be divided into two stages: 83 During the first stage (schematic diagram in Figure 6a), (i) while the perovskite polymer composite solution is heated to 60 °C, the N,N-DMF solvent begins to evaporate and PVDF crystallizes due to its relatively low solubility. It then transforms into a colorless film and remains in an intermediate state. (ii) The FAPbBr2I precursor solution portion of the perovskite polymer composite solution then begins to approach its supersaturation concentration (C0), forming nanoparticles, as indicated by a color change from colorless to red. Without wishing to be bound by any particular theory or mechanism of action, two distinct crystallization processes of PVDF and FAPbBr2I may be key components of the self-assembly process by which FAPbBr2I nanoparticles are embedded in the PVDF framework of the perovskite polymer film of the present invention.

[0043]

[0048] During the second step, the perovskite nanoparticles tend to anchor to the PVDF framework. Without wishing to be bound by any particular theory or mechanism of action, this is thought to be due to the NH3 + This can be attributed to the strong interaction between the -CF2- groups of PVDF and the -CF2- groups of PVDF. Such interaction can be expressed by the formula (ν=1304√(k / u)(cm -1 ) (where ν is the frequency, k is the force constant (N / m), and u is the effective mass), the wavenumber range of 1350–1100 cm due to the reduction of the force constant. -1 This interaction is reflected by a blue shift of the infrared absorption peak of the C—F bond in the FTIR spectrum (shown in FIG. 6b). This interaction can also be observed from the mapping of fluorine (F) and lead (Pb) atoms, which correspond to the PVDF polymer chain (FIG. 4b) and the FAPbBr2I crystal (FIG. 4c). As seen in FIG. 4c, the perovskite clusters attach to the PVDF polymer. Without wishing to be bound by any particular theory or mechanism of action, this is thought to be due to their common solubility in N,N-DMF solvent (the two materials can be grown in one step) and the NH3+ This may be due to the dipole interaction between the perovskite and the -CF2- groups of PVDF.

[0044]

[0049] The porosity and size of the pores in the perovskite polymer films of the present invention can be controlled through adjusting the mass ratio (wt%) of perovskite to polymer. The corresponding surface morphology revealed in AFM images (Figure 7) shows that the pore diameter gradually increases to approximately 7 μm at 30 wt% FAPbBr2I. During the crystallization process, the increase in mass ratio should lead to the aggregation of FAPbBr2I NPs. Without wishing to be bound by any particular theory or mechanism of action, this is believed to be due to the fact that the FAPbBr2I NPs are agglomerated. + This may be due to the above-mentioned strong dipole interactions between the cations and the anionic fluorine (-CF2-) groups of PVDF.

[0045]

[0050] A simulated perovskite polymer PNG model was constructed to demonstrate the effect of the self-assembled, highly porous characteristics of the perovskite polymer film of the present invention on the output piezopotential. This was simulated using COMSOL Multiphysics 5.3. The simulation results were compared between a pure (pore-free, solid) PVDF film and a 20% circular porous PVDF film (the circular shape was adopted from ZnO NPs). Figure 4d shows that under a uniaxial compressive stress of 800 kPa, the induced displacements of the three different PNG models (with the same film thickness of 30 μm) are different. As shown in Figure 4d, the pure PVDF film was least deformed, while the perovskite polymer film was most deformed. Without wishing to be bound by any particular theory or mechanism of action, the pore location and size affect the mechanical stress distribution, which may contribute to an increase in the average stress distribution profile inside the perovskite polymer film.

[0046]

[0051] From finite element calculations (along the cut lines in Figures 8b-c), the stress inside the pure PVDF film appears to be fairly uniform under uniaxial normal stress. In contrast, in the circular porous PVDF structure, the stress distribution is asymmetric. Compared to pure PVDF, the stress distribution in the circular porous PVDF model is disrupted by the presence of pores. In such a circular porous structure (the center model in Figure 4d), the stress is primarily confined to the periphery of each pore and is higher along the direction of the applied force, i.e., at the top and bottom sides of the pore. The local compressive strain in each pore results in bulk film strain primarily in the vertical direction (x-direction strain S1 approximately 0%, y-direction strain S2 approximately 3.4%), altering the internal coupling. The highly ordered porous structure of our perovskite polymer film (the rightmost model in Figure 4d) not only deforms along the vertical direction (S2 approximately 17%) but also significantly elongates along the horizontal direction (S1 approximately 57%). The upper stress concentration spot exerts a pushing force on the pore of the perovskite polymer film, inducing strain relaxation on two sides. Figure 8b (rightmost model) shows the characteristics of this larger pore, which promotes linear stress on the sidewall of the structure. This phenomenon is similar to the flextensional mechanism. 84~85 , which highlights structural modifications of the mechanism that can further amplify applied vertical stresses in the horizontal direction.

[0047]

[0052] Because the strain-induced piezoelectric potential is the collective result from the strains around each of the pores, the piezoelectric potential of the porous PVDF structure is therefore higher than that of the non-porous PVDF piezoelectric film (Figure 4e). The vibration-induced electrical displacement D3 (charge per unit area) is calculated as follows: D3=e 333 S 33 +|e 331 |S 31

[0053] (In the formula, e 331 and e 333 is the piezoelectric constant 86 , S 31 and S 33are the strains induced along the horizontal and vertical directions, respectively. D3 of the perovskite polymer film is synergistically affected by the bidirectional (horizontal and vertical) strains S1 (approximately 57%) and S2 (approximately 17%). Therefore, the perovskite polymer film structure significantly enhances the strain-induced piezoelectric potential or voltage output (following the parallel-plate capacitor model, V = Q / C, where Q is the total induced charge and C is the device capacitance). This is confirmed by the finite element simulations shown in Figure 4e. The finite element simulations in Figure 4e show that the maximum piezoelectric potential is approximately 40 V for the perovskite polymer film, whereas it is approximately 11 V and 15 V for the pure and 20% porous PVDF films, respectively (applied with the same stress of 800 kPa).

[0048]

[0054] It is noteworthy that perovskite polymer PNG with such a highly ordered pore array as shown will likely generate a higher electric potential than a structure with a single pore (the rightmost model in Figure 9b). In the pore array, the walls of the inner pore structure are highly compressed due to bidirectional stress (indicated by the arrows in Figure 9a). The increased stress between the pores further improves the piezoelectric potential of the perovskite polymer film. Yuan et al. reported a 2.2-fold enhancement in the piezoelectric potential of a six-layer PVDF-TrFE (trifluoroethylene)-based PNG by fabricating a rugby ball-shaped PNG structure to take advantage of the flextensional strain effect. 53 Without wishing to be bound by any particular theory or mechanism of action, the improved piezoelectric output of the perovskite polymer films of the present invention can be attributed at least in part to this amplified mechanical strain. 2.2 Energy collection performance of P-PNG

[0055] The perovskite polymer film of the present invention provides a platform for developing scalable PNGs, which require only two thin metal electrodes on either side. The microstructural features of the perovskite polymer film, along with the formation of FAPbBr2I nanocrystals, were utilized to investigate their effect on PNG performance. The fabricated device was placed on the hammer of an electrodynamic shaker and sandwiched between a 138 g stainless steel metal block (schematic diagram of the test setup shown in Figure 10). The output voltage and current generated from the periodic mechanical vibrations generated by the electrodynamic shaker were measured at various frequencies (10-50 Hz) and accelerations (1-2.5 G). An output voltage of approximately 85 V (peak-to-peak) and a short-circuit current of approximately 30 μA (peak-to-peak) were recorded from an active device area of ​​3.8 cm × 3.8 cm at 30 Hz and 2 G (results shown in Figure 11).

[0049]

[0056] Without wishing to be bound by any particular theory or mechanism of action, FIG. 12 illustrates the operating mechanism of PNGs comprising the perovskite polymer film of the present invention. In the figure, stress mapping is used to schematically illustrate the electricity generation mechanism of PNGs using finite element simulations (COMSOL Multiphysics 5.3). When no electric field is applied, the net dipole moment inside the film is nearly zero (FIG. 12a). By applying a high electric field (50-120 V / μm) for 2-3 hours, the dipoles align in the direction of the electric field (FIG. 12b). When a compressive force is then applied to the device, the flextensional strain causes a change in the net polarization in the film, thereby generating a piezoelectric potential (FIG. 12c). Due to the rapid change in net dipole moment caused by the flextensional mechanism, it is expected that the change in polarization in the poled PNGs can generate even higher electric potentials. 87~88When the two electrodes are connected together, a current flows to balance this piezoelectric potential. Upon releasing the force, the piezoelectric potential returns to zero due to the weakening of the film strain, and the accumulated electrons then flow back (Figure 12d). Due to the formation of larger porous structures, the perovskite polymer film undergoes an additional decay cycle, resulting in a second output current pulse (Figure 12e).

[0050]

[0057] The pore size (and thus porosity) of the perovskite polymer films of the present invention increases with the concentration of the FAPbBr2I precursor, which may play a key role in PNG performance. The output voltage and current were found to increase with the FAPbBr2I composition (up to approximately 85 V and approximately 30 μA at 20 wt%) and then decrease (Figure 13). PNG with 20 wt% FAPbBr2I demonstrated the highest power performance, and after a certain threshold margin, PNG performance began to decline with further addition of FAPbBr2I NPs. Without wishing to be bound by any particular theory or mechanism of action, this may be due to one or a combination of the following factors: (i) very high porosity resulting in a large reduction in PVDF per unit volume; (ii) higher mass ratios of FAPbBr2I (>20 wt%) resulting in a reduction in film impedance, thereby causing premature dielectric breakdown before the maximum polarizing charge value is achieved by the electrical poling process; and (iii) defects created by agglomeration of FAPbBr2I NPs.

[0051]

[0058] The highest measured output voltage and current of PNG with 20 wt% FAPbBr2I were compared with those of pure and 20 wt% porous PVDF-based PNG devices (Figure 13). The output voltage and current of the 20 wt% perovskite polymer PNG increased by approximately 5 times and 15 times, respectively, compared with those of the pure PVDF-based PNG model (approximately 17 V and approximately 2 μA). The output voltage and current of the 20 wt% perovskite polymer PNG were also substantially higher than those of the 20% porous PVDF PNG (approximately 40 V and approximately 6 μA). The power generation of perovskite polymer PNG originated from the unique piezoelectric polarization.89~95 , as verified by output polarity switching (Fig. 14c) showing the expected output reversal.

[0052]

[0059] The bulk material properties of the perovskite polymer films of the present invention were also investigated. The dielectric constants of the porous PVDF film and the perovskite polymer film (20 wt% FAPbBr2I@PVDF) were measured in the frequency range from 1 kHz to 1 MHz (Figure 14d). For both films, the starting dielectric constant was higher in the lower frequency regime, likely due to the interfacial polarization effect between the nanoparticles and the polymer interface. 96 This polarization effect arises from free carriers in the polymer material. However, as the applied electric field frequency increases, the interfacial polarization cannot cope with the frequency change, resulting in a decrease in the dielectric constant. The pattern of increasing relative permittivity was found to correlate with the increase in stray capacitance at high frequencies during measurements. The higher dielectric constant of the perovskite polymer film (approximately 12 at 1 kHz) enhanced the piezoelectric performance because it increased the piezoelectric coefficient (D3). 97~99 In addition, the enhanced dielectric constant of FAPbBr2I perovskite caused the output current to decrease by reducing the internal impedance (Z) of the film:

[0053]

number

[0054] where R is the resistance of the film, d is the thickness, A is the area, ε is the vacuum permittivity, and ε r is the relative permittivity).

[0055]

[0060] Due to internal polarization, the charge was also affected by the dielectric constant of FAPbBr2I. Using Kelvin probe force microscopy (KPFM), the surface potential of the perovskite polymer film was measured. The relationship between the dielectric constant and polarization can be expressed as:

[0056]

number

[0057] (In the formula,

[0058]

number

[0059] is the electric polarization in the material, and ε0 is the permittivity of free space (8.854×10 -12 Fm -1 ) and ε r is the relative permittivity,

[0060]

number

[0061] is the electric field).

[0062] From equation (4), the higher dielectric constant of the perovskite polymer film due to the presence of perovskite likely changes the strain-induced electric field inside the film, resulting in a different magnitude of the surface potential. In general, for perovskite polymer PNG, the surface potential is of particular interest because it affects band bending and carrier transport at the interface. 101~105 By measuring the contact potential difference using a platinum (Pt) KPFM tip (>20 nm radius) in intermittent contact mode, the average surface potential of the perovskite polymer film was found to be 1.1 V, more than twice that of the porous PVDF film (Figure 14e-f). The observed fluctuations in the average surface potential of the perovskite polymer film were minimal (<100 mV). This excludes the possibility of surface contamination by residual precursors—formamidine iodide (FAI) or lead bromide (PbBr).

[0063]

[0062] The vibration-dependent output voltage and current around the perovskite polymer PNG (Fig. 15) were also measured. By keeping the force constant, the frequency of the electrodynamic shaker was varied from 10 to 50 Hz by a controller unit (Vibration Research VR 9500 Rotation). The maximum output power was obtained at 30 Hz, corresponding to the resonant condition where the electromechanical coupling is at its maximum. To evaluate the flexibility of the perovskite polymer PNG, a cyclic bending force was applied at a constant strain rate (15.5 cm / sec), and the output voltage and current were measured. The peak-to-peak output voltage was 14 V and the current was 0.3 μA (Fig. 16). This could be further enhanced by increasing the bending radius. 74 . 3. Use of PNG as a green power source in IoT

[0063] A self-powered integrated wireless electronics node (SIWEN) for a distributed network of IoT was implemented using a P-PNG containing the perovskite polymer film of the present invention as a power source, which was configured to remotely communicate with Bluetooth-enabled personal electronics to transfer data from one or more distributed sensors.

[0064] The functional block diagram of the SIWEN is shown in Figure 17. The SIWEN incorporates a rectification unit, a two-stage energy transfer system, a regulated switch, and a low-power system-on-chip (SoC) for conditioning the sensor signal and transmitting it to a remote-end receiver (Figure 18). Before integrating the perovskite polymer PNG into the SIWEN, its practical load driving capability was confirmed. The maximum instantaneous power delivered to the load was measured from the output current using a wide range of external load resistances (100 KΩ to 80 MΩ), and a peak output power of approximately 105 μW was obtained with a load resistance of 7 MΩ.

[0065]

[0065] The perovskite polymer PNG captured mechanical energy from the extremely small vibrations of an electrodynamic shaker (operating at 30 Hz), stored the energy, and powered the SIWEN, initiating data transfer. The measured charge characteristics of the two-stage energy transfer system (enabled by two capacitors (Cp)) are shown in Figure 19b. When the voltage of the input capacitor (1 μF) reached approximately 5 V, it was regulated by a Zener diode and released energy to the output capacitor (220 μF) through the buck converter module. The buck converter module consisted of two metal-oxide semiconductor field-effect transistor (MOSFET) switches. After the output voltage of the 1 μF input capacitor dropped to a regulated voltage of approximately 2–3 V, the 220 μF output capacitor was disconnected from it by the MOSFET switch, and the input capacitor stopped discharging and began charging. In this way, the output capacitor was charged to approximately 3.1 V with high energy transfer efficiency, enabling it to power the universal electronics node. The electrical energy stored in a 220 μF output capacitor was used to power a Bluetooth®-enabled system-on-chip (SoC). Another perovskite polymer PNG was incorporated into the system as a sensing unit. This sensing unit was connected to the SoC's analog-to-digital converter (ADC) via an impedance matching bridge. Immediately after the output voltage of the 220 μF capacitor reached 3.1 V, a trigger signal was sent to switch on, causing the output capacitor to release energy to power the SoC and transmit digital data to a remote receiver. The entire process of energy harvesting, energy storage, data collection, and wireless transmission was demonstrated and recorded. As shown in Figure 19c, two smartphones received the transmitted data from the SIWEN and decoded the signal from the mimicked sensor (another perovskite polymer PNG).

[0066]

[0066] Perovskite polymer PNG was also used to harness vibrations from an automobile vehicle. Figure 19d shows the output voltage measured from a perovskite polymer PNG when mounted in a vehicle (engine running), where the device output reflected the engine's acceleration- and rotational speed-dependent vibration pattern. After starting the engine, the revolutions per minute (rpm) was varied from 1 to 1.5, 1.5 to 2, and 2 to 2.5 kilo-revolutions per minute (krev / min), while maintaining constant acceleration between each rpm regime. Initially, a peak-to-peak voltage of approximately 13 V was measured, likely due to a sudden engine vibration at start-up. Subsequently, the perovskite polymer PNG output dropped due to a gradual reduction in vibration magnitude at higher rpm regimes. A fast Fourier transform was performed, revealing a major contribution of the device output generated from a vibration component around 40 Hz, which is close to the resonant frequency of the perovskite polymer PNG. By harnessing the energy from these slight engine vibrations, a 1 μF commercially available capacitor was charged to 4 V in approximately 1 minute. As shown in Figure 19, the capacitor was continuously charged by switching the vehicle rpm between 1 and 1.4 krev / min (red curve), 1 and 2 krev / min (blue curve), and 0.75 and 2 krev / min (black curve). The best charging performance at 1 and 1.4 krev / min is likely due to the fastest acceleration and more frequent excitation of the capacitor (due to the lower rpm switching time). For the other two wider rpm regimes, the acceleration was lower and the longer rpm switching time allowed the capacitor to further release its energy. B. Porous PVDF film 4. Experimental Method 4.1 Fabrication of porous PVDF film

[0067] Figure 20 shows another embodiment of a composite film of the present invention, in which the substrate comprises a polymer and the piezoelectric nanoparticles comprise ZnO. This porous PVDF film was then incorporated into the illustrated PNG. To prepare the porous PVDF film, PVDF powder (Sigma Aldrich) was dissolved in N,N-dimethylformamide (DMF) solvent (10 wt%) at 70 °C for 24 hours. ZnO NPs (35–45 nm, US Research Nanomaterials, Inc.) were then mixed into the PVDF matrix solution, adjusting the mass ratio between ZnO NPs and PVDF to create different porosities. The solution was stirred on a hot plate at 45 °C for another 4 hours, followed by prolonged ultrasonic treatment for 30 minutes to maximize the uniform distribution of the ZnO NPs within the PVDF polymer matrix. The suspension was then drop-cast onto a circular Si wafer and degassed in a vacuum oven at 65 °C with N2 supply for 30 minutes to reduce bubble formation during drop-casting. Next, annealing was performed in the same vacuum oven at a slightly elevated temperature (75 °C) for another 45 min. The film was then peeled off from the substrate and immersed in a 37 wt% HCl solution for 4 h to remove the ZnO NPs from the PVDF matrix. After HCl etching, the film was washed with deionized (DI) water, dried with N2 air, and placed in a vacuum oven at 60 °C overnight for better drying. 4.2 Fabrication of porous PVDF film PNG

[0068] The porous PVDF film of the present invention is subjected to high-voltage electrical polarization treatment using a DC voltage of 0 to 6 kV and an electric field of 70 to 120 Vμm. -1 The polarization process was carried out at 1000 kV for 5-6 hours. The sample was stable throughout the entire polarization process. No short circuits or significant voltage fluctuations were detected up to a maximum voltage of 6 kV. The polarized porous PVDF film was then inserted between two copper electrodes. For characterization purposes, electrical connections were made from both the upper and lower electrodes using very thin and flexible copper conductors. Finally, the polyester / copper / porous PVDF film / copper / polyester layered structure was inserted and passed through a commercially available thermal laminator to eliminate any voids. 4.3 Characterization and Measurement

[0069] A JSM-7200F field emission scanning electron microscopy tool was used to characterize the morphology and structural properties of the porous PVDF films of the present invention. Fourier transform infrared spectroscopy (FTIR) was performed on a Nicolet iS50, ranging from 400 to 1000 cm. -1 The formation of a piezoelectric β-phase inside the porous PVDF film was confirmed by measuring characteristic absorbance peaks in the wavenumber range. Atomic force microscopy (AFM) images were recorded using a JPK Nanowizard II configured in intermittent contact mode (scan rate 0.3 Hz). To investigate the electrical output performance of the porous PVDF PNG, an electrodynamic shaker (Labworks Inc.) was used. This electrodynamic shaker was controlled by a power amplifier and controller unit. A digital oscilloscope (Tektronix 2004C) and a low-noise current preamplifier (Model-SR570, Stanford Research System Inc.) were used to record the electrical output from the PNG. 5. Results and Discussion

[0070] A self-powered wireless structural health monitoring system can be a combination of an energy generation section, an energy management circuit, and a data transmission unit (RF module). In the system shown in Figure 20(a), the PNG was placed between two metal sheets, reflecting the scenario of a PNG operating inside a mechanical joint. The device consisted of a porous PVDF film (approximately 50 μm) of the present invention, which was sandwiched between two copper electrodes and encapsulated in a polyester substrate. For wiring purposes, very thin and flexible copper wires (approximately 100 μm) were used on both the top and bottom sides of the electrodes. Finally, the polyester / copper / porous PVDF film / copper / polyester layered structure was compressed with a commercially available thermal laminator to ensure uniform adhesion between each layer and eliminate any voids. As shown in Figure 20(b), a custom-made wireless circuit was placed inside the groove of the metal sheet (as shown in Figure 20(a)), which in turn enabled energy management, storage, signal conditioning, and data transmission. The fabricated porous PVDF PNG device, with proper packaging and electrode connections for measurement purposes, is shown in Figure 20(c). Figure 20(d) describes the operation of the custom-designed wireless sensing node, where the electrical output from the porous PVDF PNG was used to power the sensing and data transmission unit. The AC electrical output collected from the porous PVDF PNG was first rectified by a bridge rectifier unit and fed to an energy management module (EMM), where the collected energy was regulated and stored in an input capacitor (1 μF) (temporary storage). Once the input capacitor was fully charged and reached approximately 5 V, it was regulated by a Zener diode and released energy to the output capacitor (220 μF) through the buck converter module, dropping the regulated voltage to approximately 2–3 V. Then, when the output capacitor (220 μF) was disconnected by the MOSFET switch of the buck converter, the input capacitor began charging again to the regulated level of approximately 5 V, continuing the charge-discharge cycle.The charging and discharging cycle of the input capacitor continued until the output capacitor was charged to approximately 3.1V, by which point it was powering the entire data transmission system.

[0067]

[0071] For sensing purposes, the AC output from the PNG was fed to the RF module via an impedance matching network (IMU), which contained a diode and an operational amplifier (Op-Amp) as shown in Figure 20(d). The RF module's RSL-10 system-on-chip (SoC) was programmed to operate for a preset interval of approximately 1 second per data transmission cycle, during which the measured sensor signal from the PNG was digitized and wirelessly transmitted to a remote receiver (a mobile phone). A delay-based output capacitor discharge level controller was introduced to control the data transmission frequency. The entire system, including the rectifier, EMM, RF module, and impedance matching unit, was integrated onto a 3-cm-diameter circular printed circuit board (PCB), as shown in Figure 20(b). The complete operation of energy collection, energy storage, data collection, and wireless transmission was systematically demonstrated and recorded. The system was tested and its operation was verified under different vibration conditions of a linear electrodynamic shaker.

[0068]

[0072] To demonstrate the ability to fabricate high-quality porous piezoelectric polymer films on a population scale, a large area porous PVDF film (approximately 15 cm × 15 cm) was fabricated using the method described above ( Figure 21(a) ).

[0069]

[0073] Figure 22(a) shows a top-view scanning electron microscopy (SEM) image of a pure PVDF film, showing the surface topography and composition of the sample; the image was homogeneous, without wrinkles, grains, voids, cracks, or deformations. Meanwhile, Figure 22(b) shows a top-view SEM image of uniformly dispersed ZnO-NPs in a porous PVDF film matrix of the present invention (the inset is the complete PVDF / ZnO NP-based PNG film). The purpose of introducing ZnO-NPs into the PVDF matrix is ​​to enhance its mechanical properties, as well as to enhance the Zn 2+ cation and PVDF CF2 - The creation of porosity in the PVDF film (by HCl etching) enhances the generation of the piezoelectric β-phase due to dipole-dipole interactions between the ZnO groups. Furthermore, compared with inorganic (e.g., SiO2) or organic (e.g., polystyrene) NPs, ZnO possesses several unique advantages for the fabrication of porous nanostructures, including cost-effectiveness, non-toxicity, good scalability, and easy removal with acidic solutions. Figure 22(b) shows that the ZnO NPs were randomly dispersed and accumulated, e.g., clusters, inside the PVDF film, likely due to their molecular weight (ZnO NPs are heavier than PVDF molecules). Figure 21(b-c) shows cross-sectional SEM images of pure PVDF and ZnO NPs dispersed within a PVDF matrix, respectively.

[0070]

[0074] After the etching process, the surface of the PVDF became significantly rough (Figure 23(a-b)). The scanning electron microscopy (SEM) image shown in Figure 22(c) shows the top surface of a porous PVDF film of the present invention after ZnO-NP removal and subsequent HCl etching, and the inset shows the porous PVDF film after HCl etching. During the etching process, hydrochloric acid (HCl) first reacted with the inorganic ZnO nanoparticles on the surface and then gradually penetrated into the PVDF film. As the ZnO NPs were randomly dispersed throughout the film, pores formed not only on the surface but throughout the film, and the pore size was larger than the actual nanoparticle size. The atomic force microscopy (AFM) image in Figure 22(d) is a three-dimensional surface topology image of the porous PVDF film. As seen in Figure 22(d), the surface roughness of the porous PVDF film is approximately 100 nm (Figures 23(a-b)).

[0071]

[0075] In addition to porosity, it is desirable to achieve β-phase crystallinity in PVDF, as the β-phase has been reported to possess the highest spontaneous polarity than the other polymorphic phases of PVDF (α, γ, δ). To confirm β-phase formation in existing porous PVDF films, a wavenumber range of 400–1000 cm was used. -1 Fourier transform infrared (FTIR) spectroscopy was performed at 431 and 840 cm -1 The characteristic peaks of the β-phase at 0001 can be observed in the FTIR spectrum of Figure 22(e). Without wishing to be bound by any particular theory or mechanism of action, the formation of the β-phase in the PVDF matrix can be attributed, at least in part, to the interaction between the dipoles of the surface charges on the PVDF and the ZnO-NPs. The positively charged Zn cations (0001 surface) and the O-terminal anions (0001 - PVDF CF2 with negative and positive charge densities on the surface - or CH2 + When high electric field poling is applied, the dipoles of PVDF align in the direction of the electric field.

[0072]

[0076] In the SHM system, mechanical vibrations from the rocking and electrodynamic shaker were transported across the surface, thus compressing the porous PVDF PNG located between the shaker hammer and the stainless steel block, thereby generating a piezoelectric output. The PNG weighing system can be modeled as a spring-mass system similar to a freely vibrating system with damping.

[0073]

[0077] Without wishing to be bound by any particular theory or mechanism of action, Figure 24 shows a schematic representation of the mechanism of electricity generation from a poled porous PVDF PNG. Initially, in the absence of any externally applied force, the net dipole moment inside the porous PVDF film is zero. When a perpendicular compressive force is applied to the device, the net polarization within the PNG changes, thus resulting in a piezoelectric potential. This causes free electrons to migrate from one electrode to the other. After the force is released, the piezoelectric potential decays and the electrons migrate back.

[0074]

[0078] As shown in Figure 25(a-b), for the 50 wt% ZnO@PVDF device, the active device area was 11.3 cm 2 The peak-to-peak output open-circuit voltage (Voc) and short-circuit current (Isc) measured at 30 Hz frequency were about 84.5 V and 22 μA, respectively. This porous PVDF PNG exhibited an approximately 11-fold (about 22 μA p-p) and an approximately 8-fold (about 84.5 V p-p) increase in output current and voltage capabilities, respectively, compared to pure PVDF. Without wishing to be bound by any particular theory or mechanism of action, the pores inside the PVDF may affect the stress distribution inside the film, boosting the strain-induced piezoelectric potential.

[0075]

[0079] Because porosity is a key factor controlling mechanical energy harvesting capability, its effect on practical PNG device performance was also examined. PVDF thin films with different porosities were prepared from mixtures of ZnO NPs with different mass ratios (wt%) (Figure 26a). As the ZnO mass fraction increased from 0 wt% (pure PVDF) to 50 wt%, the enhancement in porosity percentage further boosted the PNG output voltage from 18 V (pp) to 84.5 V (pp) when measured at a frequency of 30 Hz. However, a further increase in the ZnO mass ratio (60 wt%) reduced the output voltage to 60 V (pp) (Figure 26b). The PNG film fabricated from a mixture of 50 wt% ZnO showed the highest output performance.

[0076]

[0080] To verify the experimental results, a PNG model based on finite element simulations was developed (COMSOL Multiphysics 5.3). The model was then compared with a pure PVDF film and a 50 wt% porous PVDF film. Figures 25(c-d) show the stress distribution and output voltage of the porous PVDF film under a uniaxial compressive stress of 800 kPa, while Figure 27 shows the results for the pure PVDF film. The induced displacements and output voltages of the two PNG models with the same film thickness were different, with the porous PVDF film producing larger deformations than the pure PVDF film and therefore producing larger output voltages. Without wishing to be bound by any particular theory or mechanism, this phenomenon may be at least partially attributed to the influence of the pore location and size on the stress distribution in the PVDF film.

[0077]

[0081] As a general verification to confirm the unique piezoelectricity arising from the porous PVDF PNG, a polarity-switching test was performed. When the connection was reversed, the reversal in the open-circuit voltage (Fig. 28a) and short-circuit current (Fig. 25e) showed identical amplitudes with the reversed polarity configuration, thereby confirming the reliability of the piezoelectric output signal. The PNG output sustained under constant vibration for 36,000 cycles (20 minutes at 30 Hz) without any noticeable degradation in the output signal (Fig. 25(f)).

[0078]

[0082] To verify the suitability of the porous PVDF PNG-based SHM system, the broadband energy harvesting capability of the porous PVDF PNG in terms of open-circuit voltage (Figure 29a) and short-circuit current (Figure 28b) was measured over a frequency range of 10 Hz to 50 Hz (the frequency of the electrodynamic shaker was varied using a Vibration Research VR9500 controller unit). The piezoelectric output increased up to 30 Hz, and the maximum VOC was recorded at this point, corresponding to a resonant condition in the system and due to an increase in the required input power of the oscillator. The harvested energy was stored in commercially available capacitors of different values ​​via a full-wave bridge circuit. Figure 29(b) shows the charging characteristics of capacitors of 1.0 μF, 2.2 μF, 4.7 μF, 10 μF, 47 μF, and 100 μF up to 3 V, which took 140 seconds for the 100 μF capacitor. It has been reported that higher / faster energy storage in the input capacitor of a two-stage charging system enhances the energy transfer efficiency to the output capacitor and reduces its charging time. 46 Next, we investigated the maximum instantaneous power delivered to the load based on the output rectified current measured from a wide range of external load resistances. As presented in Figure 29(c), the peak output power (P = I 2 R) 78 μW and a corresponding peak power density of 12 μW / cm 2 was achieved with a load resistance of 7 MΩ (while the peak power and peak power density without load were 0.46 mW and 41.02 μW / cm, respectively). 2This was sufficient to drive the wireless SHM system. As shown in Figure 29(d), a porous PVDF PNG generated electrical energy from the vibration of an electrodynamic shaker operating at 30 Hz, and the rectified output charged an input capacitor (1 μF). When the charging voltage of the input capacitor reached approximately 5 V, it was regulated by a Zener diode and released energy to an output storage capacitor (220 μF) via a buck converter module. The buck converter module was enabled by two MOSFET switches. After the output voltage of the 1 μF capacitor dropped to a regulated voltage of approximately 2–3 V, the 220 μF capacitor was disconnected by a MOS switch, and the input capacitor began charging again. In this way, the output capacitor charged to approximately 3.1 V with high energy transfer efficiency, powering a universal electronics node. This voltage in this particular example drove a Bluetooth®-enabled system-on-chip (SoC). Another porous PVDF PNG device was incorporated as a sensing unit, connected to the SoC's analog-to-digital converter (ADC) via an impedance-matching bridge. Shortly after the output voltage of the 220 μF capacitor reaches 3.1 V, the digital signal activates the switch, through which the output capacitor releases energy, triggering the SoC to transmit the sensor's ADC-sampled data points to the remote receiver. Figure 29(e) shows the setup, in which the device is fixed on top of a linear mechanical shaker and weighted with a standard mass of 130 grams. Figure 29(f) shows the smartphone's Bluetooth receiver simultaneously receiving and decoding the mimicked sensor signal.

[0079]

[0083] The present invention has been described with reference to illustrative embodiments and examples, and the specification is not intended to be construed in a limiting sense. Thus, various modifications of the illustrative embodiments, as well as other embodiments of the present invention, will become apparent to those skilled in the art upon reference to this specification. It is therefore intended that the appended claims cover any such modifications or embodiments.

[0080]

[0084] All publications, patents, and patent applications referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference in its entirety. The following additionally describes embodiments of the present invention. [1] A film comprising a perovskite and a polymer, wherein the perovskite and the polymer are configured to form a plurality of elongated pores. [2] The film of [1], wherein the film comprises two opposing major surfaces interconnected by the pores. [3] The film described in [2], wherein the pores are aligned at least partially perpendicular to the two opposing major surfaces of the film. [4] The film according to any one of [1] to [3], wherein the pores are deformed when a force is applied to the main surface of the film. [5] The film according to any one of [1] to [4], wherein the pores have a length of about 20 μm to 25 μm. [6] The film according to any one of [1] to [5], wherein the pores have a diameter of about 3 μm to about 5 μm. [7] The film according to any one of [1] to [6], wherein the perovskite contains nanoparticles. [8] The film according to any one of [1] to [7], wherein the perovskite is embedded in the polymer. [9] The film according to any one of [1] to [8], wherein the film contains the perovskite in a crystalline form.

[10] The film according to [9], wherein the perovskite crystals comprise a non-centrosymmetric structure.

[11] The film according to any one of [1] to

[10] , wherein the perovskite comprises a hybrid halide perovskite.

[12] The perovskite is (HHP)-formamidinium lead bromide iodide (FAPbBr 2 The film according to

[11] , comprising:

[13] The film according to any one of [1] to

[12] , wherein the film contains the polymer in a crystalline β phase.

[14] The film according to any one of [1] to

[13] , wherein the polymer is selected from the group consisting of polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), and polyethyl acrylate (PEA).

[15] The film according to any one of [1] to

[14] , wherein the polymer comprises polyvinylidene fluoride (PVDF).

[16] The film according to any one of [1] to

[16] , wherein the film contains the perovskite in a mass ratio of about 10% by weight to about 30% by weight.

[17] The film according to

[16] , wherein the film comprises the perovskite in a mass ratio of about 20 wt %.

[18] The film according to any one of [1] to

[17] , wherein the film contains the polymer in a mass ratio of about 10% by weight to about 15% by weight.

[19] The film according to

[18] , wherein the film contains the polymer in a mass ratio of about 10% by weight.

[20] The film according to any one of [1] to

[19] , wherein the film comprises a plurality of dipoles, and the dipoles are substantially aligned.

[21] The film according to any one of [1] to

[20] , wherein the film has a thickness of about 20 μm to about 50 μm.

[22] The film of

[21] , wherein the film has a thickness of about 30 μm.

[23] The film according to any one of [1] to

[22] , wherein the film is formed by a two-step crystallization method.

[24] a. The film according to any one of [1] to

[20] . b. a first electrode; and c. Second electrode wherein the film is in electrical contact with the first electrode and the second electrode.

[25] The piezoelectric nanogenerator according to

[24] , wherein the first electrode comprises a metal or a polymer.

[26] The piezoelectric nanogenerator according to

[25] , wherein the first electrode comprises a metal selected from the group consisting of copper, gold, and aluminum.

[27] The piezoelectric nanogenerator according to

[25] , wherein the first electrode comprises poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS).

[28] The piezoelectric nanogenerator according to any one of

[25] to

[27] , wherein the second electrode comprises a metal or a polymer.

[29] The piezoelectric nanogenerator according to

[28] , wherein the second electrode comprises a metal selected from the group consisting of copper, gold, and aluminum.

[30] The piezoelectric nanogenerator according to

[28] , wherein the second electrode comprises poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS).

[31] The piezoelectric nanogenerator according to any one of

[24] to

[30] , wherein the nanogenerator is encapsulated in a substrate.

[32] The piezoelectric nanogenerator according to

[31] , wherein the substrate comprises polyester.

[33] The piezoelectric nanogenerator according to

[31] or

[32] , wherein the nanogenerator is encapsulated using a thermal lamination method.

[34] An aircraft structural health monitoring system incorporating the piezoelectric nanogenerator described in any one of

[24] to

[33] .

[35] A self-powered device incorporating a piezoelectric nanogenerator according to any one of

[24] to

[33] .

[36] The self-powered device of

[35] , wherein the device is a wearable electronic device, a medical diagnostic device, or an implantable device.

[37] A method for producing a film, comprising: a. preparing a first solution by adding a polymer to a first solvent; b. preparing a second solution by adding a perovskite to a second solvent; c. homogeneously mixing the first solution with the second solution to create a mixture; and d. maintaining the mixture at a substantially constant temperature to crystallize the polymer and the perovskite. A method comprising:

[38] The method of

[37] , wherein the mixture is then cast and annealed to form a film.

[39] The method of

[38] , wherein the film is then poled using a high voltage electric poling process.

[40] The method according to any one of

[37] to

[39] , wherein the polymer crystallizes before the perovskite crystallizes.

[41] The method according to any one of

[37] to

[40] , wherein the first solution contains the polymer in a mass ratio of about 10% by weight to about 15% by weight.

[42] The method according to

[41] , wherein the first solution contains the polymer in a mass ratio of about 10% by weight.

[43] The method according to any one of

[37] to

[42] , wherein the second solution contains the perovskite in a mass ratio of about 10 wt % to about 30 wt %.

[44] The method of

[43] , wherein the second solution contains the perovskite in a mass ratio of about 20 wt. %.

[45] The method according to any one of

[37] to

[44] , wherein the first solvent is N,N-dimethylformamide.

[46] The method according to any one of

[37] to

[45] , wherein the second solvent is N,N-dimethylformamide.

[47] The method according to any one of

[35] to

[46] , wherein the mixture is maintained at a temperature of about 60°C.

[48] ​​The method according to any one of

[35] to

[47] , wherein the polymer is selected from the group consisting of polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), and polyethyl acrylate (PEA).

[49] The method of

[48] , wherein the polymer comprises PVDF.

[50] The method according to any one of

[35] to

[49] , wherein the perovskite comprises a hybrid halide perovskite.

[51] The perovskite is FAPbBr 2 The method according to

[50] , including I.

[52] A film produced by the method according to any one of

[35] to

[51] .

[53] A piezoelectric nanogenerator comprising a film produced by the method according to any one of

[35] to

[51] .

[54] A composite film comprising a substrate and a plurality of piezoelectric nanoparticles, the substrate and nanoparticles configured to form a plurality of pores, the composite comprising two opposing major surfaces interconnected by the pores.

[55] The composite film according to

[54] , wherein the substrate is a polymer.

[56] The composite film according to

[55] , wherein the polymer is in a crystalline β phase.

[57] The composite film according to

[56] , wherein the polymer is PVDF.

[58] The composite film according to any one of

[54] to

[58] , wherein the piezoelectric nanoparticles contain perovskite.

[59] The composite film of

[58] , wherein the perovskite comprises a hybrid halide perovskite.

[60] The perovskite is (HHP)-formamidinium lead bromide iodide (FAPbBr 2 The composite film according to

[59] , comprising:

[61] The composite film according to any one of

[54] to

[60] , wherein the pores are elongated.

[62] A composite film according to any one of

[54] to

[61] , wherein the pores are at least partially aligned perpendicularly to the two opposing main surfaces of the composite film.

[63] The composite film according to any one of

[54] to

[57] , wherein the piezoelectric nanoparticles contain zinc oxide (ZnO) nanoparticles.

[64] The composite film of

[63] , wherein the ZnO nanoparticles are randomly dispersed throughout the composite film.

[65] The composite film according to

[63] or

[64] , wherein the composite film contains the ZnO nanoparticles in a mass ratio of about 10% by weight to about 50% by weight.

[66] The composite film according to

[65] , wherein the composite film contains the ZnO nanoparticles in a mass ratio of about 50% by weight.

[67] The composite film according to any one of

[63] to

[66] , wherein the ZnO nanoparticles have a diameter of about 25 nm to about 55 nm.

[68] The composite film according to

[67] , wherein the ZnO nanoparticles have a diameter of about 35 nm to about 45 nm.

[69] The composite film according to any one of

[63] to

[68] , wherein the ZnO nanoparticles are dispersed throughout the composite film by ultrasonic treatment.

[70] The composite film according to any one of

[63] to

[69] , wherein the piezoelectric nanoparticles are removed from the composite film.

[71] a. The composite film according to any one of

[54] to

[70] ; b. a first electrode; and c. a second electrode; wherein the film is in electrical contact with the first electrode and the second electrode.

[0081] Thanks for watching [ PubMed ] 1. Soci C, Zhang A, Xiang B, Dayeh SA, Aplin D, Park J, Bao X, Y-H. Lo and D. Wang, Nano Lett. 2. Y. Qi and M. Mcalpine, Energy Environ. Sci., 2010, 3, https: / / doi.org / 10.1103 / PhysRevLett.111.111012 , Google Scholar Crossref , CAS 3. Yang RS, Qin Y, Dai LM and Wang ZL, Nat. Nanotechnol., 2009, 4, 4. Choi MY, Choi D., Jin MJ, Kim I, Kim SH, Choi JY, Lee SY, Kim JM and Kim SW, Adv. Mater., 2009, 21, https: / / doi.org / 10.1103 / PhysRevLett.101.1101 , Google Scholar Crossref , CAS 5. T. Xu, X. Ding, Y. Huang, C. Shao, L. Song, X. Gao, Z. Zhang, and L. Qu, Energy Environ. Sci., 2019, 12, 6. Y. F. Hu, Y. Zhang, C. Xu, L. Lin, R. L. Snyder and Z. L. Wang, Nano Lett., 2011, 11, 2572. 7. C. L. Sun, J. Shi, D. J. Bayerl and X. D. Wang, Energy Environ. Sci., 2011, 4, 4508. 8. G.-T. Hwang, H. Park, J.-H. Lee, S. Oh, K.-I. Park, M. Byun, H. Park, G. Ahn, C. K. Jeong, K. No, H. Kwon, S.-G. Lee, B. Joung and K. Jae, Adv. Mater., 2014, 26, 4880. 9. X. Qing, W. Li, Y. Wang and H. Sun, Sensors, 2019, 19, 545. 10. M. H. F. Alibadi, Z. S. Khodaei, World Scientific Publishing Europe Ltd. London, UK, 2018. 11. W. Staszewski, S. Mahzan, and R. Traynor, Compos. Sci. Technol. 2009, 69, 1678. 12. L. Qiu, S. Yuan, C. Boller, Struct. Health Monit. 2017, 16, 501. 13. M. Q. Le, J. F. Capsal, M. Lallart, Y. Hebrard, A.V. D. Ham, N. Reffe, L. Geynet, and P. J. Cottinet, Prog. Aerosp. Sci., 2015, 79, 147. 14. S. Wang, Z. L. Wang and Y. Yang, Adv. Mater., 2016, 28, 2881. 15. S. Jang, H. Kim, Y. Kim, B. J. Kang and J. H. Oh, Appl. Phys. Lett., 2016, 108, 143901. 16. C. Kumar, A. Gaur, S. Tiwari, A. Biswas, S. K. Rai and P. Maiti, Composites Communications, 2019, 11, 56. 17. S. S. Won, M. Sheldon, N. Mostovych, J. Kwak, B. S. Chang, C. W. Ahn, A. I. Kingon, I. W. Kim and S. H. Kim, Appl. Phys. Lett., 2015, 107, 202901. 18. S. J. Park, S. H. Lee, M. L. Seol, S. B. Jeon, H. Bae, D. Kim, G. H. Cho, Y. K. Choi, Nano Energy, 2019, 55, 115. 19. T. X. Xiao, X. Liang, T. Jiang, L. Xu, J. J. Shao, J. H. Nie, Y. Bai, W. Zhong, Z. L. Wang, Adv. Funct. Mater., 2018, 28, 1802634. 20. I. Sari, T. Balkan, H. Kulah, Sens. Actuators A Phys., 2018, 145, 405. 21. C.R. Saha, T.O’Donnell, N. Wang, P. McCloskey, Sens. Actuators A Phys., 2008, 147, 248. 22. S.P. Beeby, R.N. Torah, M.J. Tudor, P. Glynne-Jones, T. O’Donnell, C.R. Saha, S. Roy, J. Micromech. Microeng., 2007, 17 1257. 23. P.D. Mitcheson, P. Miao, B.H. Stark, E.M. Yeatman, A.S. Holmes, T.C. Green, Sens. Actuators A Phys., 2004, 115, 523. 24. H. Tian, S. Ma, H. M. Zhao, C. Wu, J. Ge, D. Xie, Y. Yang, T. L. Ren, Nanoscale, 2013, 5, 8951. 25. Z.L. Wang, J. Song, Science., 2006, 312, 242. 26. F.R. Fan, Z.Q. Tian, Z. L. Wang, Nano Energy, 2012, 1, 328. 27. W. Liu, Z. Wang, G. Wang, G. Liu, J. Chen, X. Pu, Y. Xi, X. Wang, H. Guo, C. Hu, Z. L. Wang, Nat. Commun., 2019,10, 1426. 28. A.A. Khan, A. Mahmud, S. Zhang, S. Islam, P. Voss, D. Ban, Nano Energy, 2019, 62, 691. 29. Z. L. Wang, T. Jiang, L. Xu, Nano Energy, 2017, 39, 9. 30. J. Nie, Z. Ren, J. Shao, C. Deng, L. Xu, X. Chen, M. Li, Z. L. Wang, ACS Nano, 2018, 12, 491. 31. Y. Bai, C. B. Han, C. He, G. Q. Gu, J. H. Nie, J. J. Shao, T. X. Xiao, C. R. Deng, Z. L. Wang, Adv. Funct. Mater., 2018, 28, 1706680. 32. X. Cao, M. Zhang, J. Huang, T. Jiang, J. Zou, N. Wang, Z. L. Wang, Adv. Mater., 2018, 30, 1704077. 33. D. H. Kim, H. J. Shin, H. Lee, C. K. Jeong, H. Park, G. T. Hwang, H. Y. Lee, D. J. Joe, J. H. Han, S. H. Lee, J. Kim, B. Joung, K. J. Lee, Adv. Funct. Mater., 2017, 27, 1700341. 34. H. S. Wang, C. K. Jeong, M. H. Seo, D. J. Joe, J. H. Han, J. B. Yoon, K. J. Lee, Nano Energy, 2017, 35, 415. 35. S. Li, J. Wang, W. PNG, L. Lin, Y. Zi, S. Wang, G. Zhang, Z. L. Wang, Adv. Energy Mater., 2017, 7, 1602832. 36. J. Chen, H. Guo, X. He, G. Liu, Y. Xi, H. Shi, C. Hu, ACS Appl. Mater. Interfaces, 2016, 8, 736. 37. A. A. Khan, A. Mahmud, D. Ban, IEEE Transactions on Nanotechnology, 2018, 18, 21. 38. J. Chen, Y. Huang, N. Zhang, H. Zou, R. Liu, C. Tao, X. Fan and Z. L. Wang, Nat. Energy, 2016, 1, 16138. 39. X. Guan, B. Xu, J. Gong, Nano Energy, 2020, 70, 104516. 40. V. Jella, S. Ippili, J. Eom, J.H Choi, S.G. Yoon, Nano Energy, 2018, 53, 46. 41. R. Ding, X. Zhange, G. Chen, H. Wang, R. Kishor, J. Xiao, F. Gao, K. Zeng, X. Chen, X. W. Sun, Y. Zheng, Nano Energy, 2017, 37, 126. 42. C. Hu, L. Cheng, Z. Wang, Y. Zheng, S. Bai and Y. Qin, Small, 2016, 12, 1315. 43. Y. Hu, C. Xu, Y. Zhang, L. Lin, R.L. Snyder, Z.L. Wang, Adv. Mater., 2011, 23, 4068. 44. S. N Cha, S. M Kim, H. Kim, J.Ku, J. I. Sohn, Y. J. Park, B. G. Song, M. H. Jung, E. K. Lee, B. L. Choi, J. J. Park, Z. L. Wang, J. M. Kim, K. Kim, Nano Lett. 2011, 11, 5142. 45. S. Lu, Q. Liao, J. Qi, S Liu, Y Liu, G. Zhang, Y. Zhang, Nano Res. 2016, 9, 372. 46. J. Li, S. Chen, W. Liu, R. Fu, S. Tu, Y. Zhao, L. Dong, B. Yan, Y. Gu, J. Phys. Chem. C, 2019, 123, 11378. 47. Y. Su, K. Gupta, Y. Hsiao, R. Wang and C. Liu, Energy Environ. Sci., 2019, 12, 410. 48. Y. Mao, P. Zhao, G. McConohy, H. Yang, Y. Tong, X. Wang, Adv. Energy Mater., 2014, 4, 1301624. 49. G. Zhang, P. Zhao, X. Zhang, K. Han, T. Zhao, Y. Zhang, C. K. Jeong, S. Jiang, S. Zhang and Q. Wang, Energy Environ. Sci., 2018, 11, 2046. 50. C. R. Bowen, H. A. Kim, P. M. Weaver and S. Dunn, Energy Environ. Sci., 2014, 7, 25. 51. D. Chen, K. Chen, K. Brown, A. Hang, J. X. J. Zhang., Appl. Phys. Lett., 2017, 110, 153902. 52. Z. Zhang, C. Yao ,Y. Yu, Z. Hong, M. Zhi, X. Wang, Adv. Funct. Mater, 2016, 26, 6760. 53. X. Yuan, X. Gao, J. Yang, X. Shen, Z. Li, S. You, Z. Wang and S. Dong, Energy Environ. Sci., 2020, 13, 152. 54. J.‐H. Lee, K. Y. Lee, M. K. Gupta, T. Y. Kim, D.-Y. Lee, J. Oh, C. Ryu, W. J. Yoo, C.‐Y. Kang, S. -Y. Yoon, J.‐B. Yoo, S. ‐W. Kim, Adv. Mater., 2013, 26, 765. 55. J. Zhu, W. Song, F. Ma, H. Wang, Mater. Res. Bull., 2018, 102, 130. 56. K. Zhang, S. Wang and Y. Yang, Adv. Energy Mater., 2017, 7, 1601852. 57. C.‐H. Wang, W.-S. Liao, Z.-H. Lin, N.-J. Ku, Y.-C. Li, Y.-C. Chen, Z. L. Wang, C.-P. Liu, Adv. Energy Mater., 2014, 4, 1400392. 58. X. Xue, Y. Nie, B. He, L. Xing, Y. Zhang, Z. L. Wang, Nanotechnology 2013, 24, 22. 59. Y. Fu, W. Zang, P. Wang, L. Xing, X. Xue, Y. Zhang, Nano Energy, 2014, 8, 34. 60. S. A. Han, T. ‐H. Kim, S. K. Kim, K. H. Lee, H. ‐J. Park, J. ‐H. Lee, S. ‐W. Kim, Adv. Mater., 2018, 30, 1800342. 61. A. Mahmud, A.A Khan, P. Voss, T. Das, E. Abdel-Rahman, D. Ban, Adv. Mater. Interfaces, 2018, 5, 1801167. 62. J.H. Jung, M. Lee, J. Hong, Y. Ding, C. Chen, L. Chou, Z.L. Wang, ACS Nano, 2011, 5,10041. 63. S. Xu, Y.-W. Yeh , G. Poirier , M. C. Mcalpine , R. A. Register ,N. Yao , Nano Lett., 2013, 13, 2393. 64. G. Romano, G. Mantini, A. D. Carlo, A. D'Amico, C. Falconi, Z. L. Wang, Nanotechnology, 2011, 22, 465401. 65. K. I. Park, S. Xu, Y. Liu, G. T. Hwang, S. J. L. Kang, Z. L. Wang and K. J. Lee, Nano Lett., 2010, 10, 493. 66. C. K. Jeong, I. Kim, K. I. Park, M. H. Oh, H. Paik, G. T. Hwang, K. No, Y. S. Nam and K. J. Lee, ACS Nano, 2013, 7, 11016. 67. S. -H. Shin, Y. -H. Kim, M. H. Lee, J. -Y. Jung, J. H. Seol, J. Nah, ACS Nano, 2014, 8, 10844. 68. C. Baek, J. H. Yun, J. E. Wang, C. K. Jeong, K. J. Lee, K. I. Park and D. K. Kim, Nanoscale, 2016, 8, 17632. 69. K. I. Park, M. Lee, Y. Liu, S. Moon, G. T. Hwang, G. Zhu, J. E. Kim, S. O. Kim, D. K. Kim, Z. L. Wang and K. J. Lee, Adv. Mater., 2012, 24, 2999. 70. C. K. Jeong, K. I. Park, J. Ryu, G. T. Hwang and K. J. Lee, Adv. Funct. Mater., 2014, 24, 2620. 71. K. Shi, B. Sun, X. Huang, P. Jiang, Nano Energy, 2018, 52, 153. 72. S.K. Ghosh, A. Biswas, S. Sen, C. Das, K. Henkel, D. Schmeisser, D. Mandal, Nano Energy, 2016, 30, 30621. 73. Y.L. Zhao, Q.L. Liao, G.J. Zhang, Z. Zhang, Q.J. Liang, X.Q. Liao, Y. Zhang, Nano Energy, 2015, 11, 719. 74. B.S. Lee, J. Yoon, C. Jung, D.Y. Kim, S.Y. Jeon, K.H. Kim, J.H. Park, H. Park, K.H. Lee, Y.S. Kang, J.H. Park, H. Jung, W.R. Yu, S.G. Doo, ACS Nano, 2016, 10, 2617. 75. E. J. Lee, T. Y. Kim, S. Kim, S. Jeong, Y. Choi and S. Y. Lee, Energy Environ. Sci., 2018, 11, 1425. 76. A. Sultana, M. Alam, P. Sadhukhan, U.K.Ghorai, S. Das, T.R. Middya, D. Mandal, Nano Energy, 2018, 49, 380. 77. R. Ding, H. Liu, X. Zhang, J. Xiao, R. Kishor, H. Sun, B. Zhu, G. Chen, F. Gao, X. Feng, J. Chen, X. Chen, X. Sun, Y. Zheng, Adv. Funct. Mater. , 2016, 26, 7708. 78. S. K. Ghosh, T. K. Sinha, B. Mahanty, D. Mandal, Energy Technology, 2015, 3, 1190. 79. A. Sultana, P. Sadhukhan, M. M. Alam, S. Das, T. R. Middya, D. Mandal, ACS Applied Materials & Interfaces, 2018, 10, 4121. 80. S. K. Ghosh, T. K. Sinha, B. Mahanty, S. Jana, D. Mandal, J. Appl. Phys., 2016, 120, 174501. 81. W. Ma, J. Zhang, S. Chen, X. Wang, J. Macromol. Sci., 2008, 47, 434. 82. H.L.W. Chan, M.C. Cheung, C.L. Choy, Ferroelectrics, 1999, 224, 113. 83. Q. Zhou, Z. Bai, W. Lu, Y. Wang, B. Zou, H. Zhong, Adv. Mater., 2016, 28, 9163. 84. X. Li, M. Guo and S. Dong, IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 2011, 58, 698. 85. H.-X. Zou, W.-M. Zhang, W.-B. Li, Q.-H. Gao, K.-X. Wei, Z.-K. PNG, G. Meng, Smart Materials and Structures, 2017, 2611. 86. X. Gao, J. Wu, Y. Yu, Z. Chu, H. Shi and S. Dong, Adv. Funct. Mater. , 2018, 28, 1706895. 87. W. Yang, W. Gong, C. Hou.et al. Nat Commun., 2019, 10, 5541. 88. Q. Sun, W. Seung, B.J. Kim, S. Seo, S.-W. Kim, J.H. Cho, Adv. Mater.,2015, 27, 3411. 89. Z. L. Wang, J. Chen and L. Lin, Energy Environ. Sci., 2015, 8, 2250. 90. W. L. Wang, , K. J. Liao, C. G. Hu, S. X. Wang, C. Y. Kong and H. Y. Liao, Sensors and Actuators A: Physical, 2003, 108, 55. 91. T. Quan, Y. Yang, Nano Res., 2016, 9, 2226. 92. W. Seung, H.-J. Yoon ,T.Y. Kim, H. Ryu , J. Kim , J. ‐H. Lee ,, S. Kim, Y. K. Park , Y. J. Park, S. ‐W. Kim, Adv. Energy Mater. 2017, 7, 160098. 93. S. Qin, Q. Zhang, X. Yang, M. Liu, Q. Sun, Z. L. Wang, Adv. Energy Mater.,2018, 8, 1800069. 94. J. Luo, Z. Wang, L. Xu, A. Wang, K. Han, T. Jiang, Q. Lai, Y. Bai, W. Tang, F. R. Fan, Z. L. Wang, Nat Commun., 2019, 10, 5147. 95. S. Priya, J. Electroceram., 2007, 19, 167. 96. S. Luo, Y. Shen, S. Yu, Y. Wan, W. Liao, R. Sun and C. Wong, Energy Environ. Sci., 2017, 10, 137. 97. A. Jain, P. K. J. , A. K. Sharma, A. Jain, R. P.N , Polym. Eng. Sci., 2015, 55, 158. 98. R. Fries, A.J. Moulson, J. Mater. Sci.: Mater. Electron. , 1994, 5, 238. 99. T. Zheng, H. Wu, Y. Yuan, X. Lv, Q. Li, T. Men, C. Zhao, D. Xiao, J. Wu, K. Wang, J. Li, Y. Gu, J. Zhu and S. J. Pennycook, Energy Environ. Sci., 2017, 10, 52. 100. S. Sadewasser, T. Glatzel, S. Schuler, S. Nishiwaki, R. Kaigawa and M. C. Lux-Steiner, Thin Solid Films, 2003, 257, 431. 101. H. R0ehm, T. Leonhard, M. J. Hoffmann and A. Colsmann, Energy Environ. Sci., 2017, 10, 950. 102. A. D. Schulz, H. Roehm, T. Leonhard, S. Wagner, M. J. Hoffmann, A. Colsmann, Nat. Mater., 2019, 18, 1050. 103. A. H. Rahmati, S. Yang, S. Bauer and P. Sharma, Soft Matter, 2019, 15, 127. 104. A. Kuchler, High Voltage Engineering: Fundamentals-Technology-Applications, Springer Vieweg, Berlin, Germany 2018, 79. 105. K. Wang, Y. Hou, B. Poudel, D. Yang, Y. Jiang, M.‐G. Kang, K. Wang, C. Wu, S. Priya, Adv. Energy Mater., 2019, 9, 1901753. 106. KI Park, CK Jeong, J. Ryu, GT Hwang and KJ Lee, Adv. Energy Mater., 3 (12) 2013, 1539-1544. 107. J. Yan and YG Jeong, , ACS Appl. Matter. Interfaces, 8 (24) (2016) 15700-15709. 108. JM Wu, C. Xu, Y. Zhang, and ZL Wang, 6 (5) (2012) 4335-4340. 109. J. Kumar, A. Gaur, SK Rai and P. Maiti, , Nano-Struct. Nano-Objects,12 (2017) 174-181. 110. A. Gaur, R. Shukla, B. Kumar, A. Pal, S. Chatterji, R. Ranjan and P. Maiti, , Polymer, 97 (2016) 362-369. 111. RA Whiter, V. Narayan and SK Narayan, Adv. Energy Mater., 4 (18) (2014) 1400519. 112. S. Paria, SK Karan, R. Bera, AK Das, A. Maitra and BB Khatua, Ind. Eng. Chem. Res., 55 (40) (2016) 10671-10680. https: / / doi.org / 10.1103 / PhysRevLett.91.113111 , Google Scholar Crossref , CAS 113. A. Gaur, S. Tiwari, C. Kumar and P. Maiti, Nanoscale Advances. Advanced Energy Materials 6 (2016) 114. SK Karan, R Bera, S Paria, AK Das, S Maiti, A Maitra, BB Khatua. https: / / doi.org / 10.1103 / PhysRevLett.115.1155 , K. Shi, B. Sun, X. Huang, P. Jiang, Nano Energy 52 (2018) 153–162. https: / / doi.org / 10.1103 / PhysRevLett.116.116699 , Google Scholar Crossref , CAS 116. P. Thakur, A. Kool, NA Hoque, B. Bagchi, F. Khatun, P. Biswas, D. Brahma, S. Roy, S. Banerjee, S. Das, Nano Energy 44 (2018) 456-467. https: / / doi.org / 10.1103 / PhysRevLett.117.117101 , Google Scholar Crossref , CAS 117. X. Chou, J. Zhu, S. Qian, X. Niu, J. Qian, X. Hou, J. Mu, W. Geng, J. Cho, J. He, C. Xue, Nano Energy 53 (2018) 550–558. https: / / doi.org / 10.1103 / PhysRevLett.118.118201 , Google Scholar Crossref , CAS 118. S. Ye, C. Cheng, X. Chen, X. Chen, J. Shao, J. Zhang, H. Hu, H. Tian, ​​X. Li, L. Ma, and W. Jia, Nano Energy 60 (2019) 701–714. 119. H. Zhong, J. Xia, F. Wang, H. Chen, H. Wu, S. Lin, Adv. Funct. Mater., 27 (2017) https: / / doi.org / 10.1103 / PhysRevLett.115.115101 , Google Scholar Crossref 120. X. Chen, H. Tian, ​​X. Li, J. Shao, Y. Ding, N. An, and Y. Zhou, Nanoscale 7 (2015). 121. S. K. Ghosh, D. Mandal, Nano Energy, 53 (2018) 245-257. 122. M. O. G. Nayeem, S. Lee, H. Jin, N. Matsuhisa, H. Jinno, A. Miyamoto, T. Yokota, and T. Someya, PNAS, 13 (117) (2020) 7063-7070.

Claims

1. 1. A film comprising a perovskite and a polymer, the perovskite and the polymer configured to form a plurality of elongated pores, the film comprising two opposing major surfaces interconnected by the pores, the pores being aligned at least partially perpendicular to the two opposing major surfaces of the film, and wherein the pores deform when a force is applied to the major surfaces of the film.

2. 10. The film of claim 1, wherein the pores are about 20 μm to 25 μm in length.

3. 10. The film of claim 1, wherein the pores have a diameter of about 3 μm to about 5 μm.

4. and a plurality of piezoelectric nanoparticles including the perovskite, wherein the perovskite is selected from inorganic lead zirconate titanate (PZT), barium titanate (BaTiO ３ ), Na / KNbO ３ , and ZnSnO ３ The film of claim 1 , comprising at least one of:

5. The film described in claim 4, wherein the piezoelectric nanoparticles include zinc oxide (ZnO) nanoparticles.

6. 10. The film of claim 1, wherein the perovskite is in a crystalline form, and the crystalline form of the perovskite crystals comprises a non-centrosymmetric structure.

7. The perovskite comprises a hybrid halide perovskite, the hybrid halide perovskite being (HHP)-formamidinium lead bromide iodide (FAPbBr ２ 10. The film of claim 1, wherein the film is I).

8. The film of claim 1 , wherein the film comprises the polymer in a crystalline beta phase.

9. 2. The film of claim 1, wherein the polymer is selected from the group consisting of polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), and polyethyl acrylate (PEA).

10. 10. The film of claim 1, wherein the film comprises the perovskite in a mass ratio of about 10% to about 30% by weight.

11. The film of claim 1 , wherein the film comprises the polymer in a mass ratio of about 10% to about 15% by weight.

12. The film of claim 1 , wherein the film comprises a plurality of dipoles, the dipoles being substantially aligned.

13. The film of claim 1, wherein the film has a thickness of about 20 μm to about 50 μm.

14. a. the film of claim 1; b. a first electrode, and c. Second electrode wherein the film is in electrical contact with the first electrode and the second electrode.

15. 15. An aircraft structural health monitoring system incorporating the piezoelectric nanogenerator of claim 14.

16. A self-powered device incorporating the piezoelectric nanogenerator of claim 14.

17. 1. A method for producing a film, comprising: a. preparing a first solution by adding a polymer to a first solvent; b. preparing a second solution by adding a perovskite to a second solvent; c. homogeneously mixing the first solution with the second solution to create a mixture; and d. maintaining the mixture at a substantially constant temperature to crystallize the polymer and the perovskite, and then casting and annealing the mixture to form the film of claim 1; A method comprising:

18. 18. The method of claim 17, comprising crystallizing the polymer prior to crystallizing the perovskite.

Images