Piezoelectric composite film comprising organometal halide perovskite and method of making same

Abstract

A piezoelectric composite film comprising an organometal halide perovskite (OHP) is provided. The OHP comprises FAPbX2I and polystyrene, where X is a halide such as bromium. The piezoelectric composite film may be part of a piezoelectric nanogenerator or cascade piezoelectric nanogenerator.

Description

PIEZOELECTRIC COMPOSITE FILM COMPRISING ORGANOMETAL HALIDE PEROVSKITE AND METHOD OF MAKING SAMETECHNICAL FIELD

[0001] The disclosure relates generally to a composite film, and more particularly to a piezoelectric composite film .BACKGROUND

[0002] Piezoelectric nanogenerators (PENG) use the piezoelectric effect for harnessing ambient vibrations to trickle charging modern electronic devices and sensing networks. Due to their unique merits in compact size, weight, and stability in harsh environments, PENGs are considered one of the most suitable energy harvesting technologies in recent years to be used with wearable, flexible, and implantable sensing platforms. Piezoceramics such as Pb(ZrTi)O3(PZT), BaTiO3(BTO), Pb (Zni / 3Nb2 / 3)O3-PbTiO3(PZN-PT), Sm-Pb(Mgi / 3Nb2 / 3)O3-PbTiO3(Sm-PMN-PT) are the dominant materials of choice for PENG applications due to their large piezoelectric charge constants. However, the brittle nature and cost of Piezoceramics pose challenges in various applications. Consequently, flexible polymers like poly (vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-trifluoro ethylene) (PVDF-TrFE), polydimethylsiloxane (PDMS), etc. may be used as host matrices in conjunction with piezoceramic fillers. Nevertheless, use of polymers may negatively impact voltage and current outputs due to defect proliferation, and may reduce the breakdown strength of the film, i.e. the capability to withstand an electric field, which hampers electrical poling.SUMMARY

[0003] An object of the present application is to provide a piezoelectric composite film comprising an organometal halide perovskite for use in Piezoelectric Nanogenerators (PENG) which provide improved current density and breakdown strength.

[0004] In one aspect, the disclosure describes a piezoelectric composite film comprising an organometal halide perovskite (OHP), the OHP comprising FAPbX2l and polystyrene, where X is a halide, preferably X is Bromine (Br).

[0005] In an embodiment, the OHP comprises about 0.1-20 wt% / vol% polystyrene with FAPbX2l.

[0006] In an embodiment, the OHP comprises about 1 wt% / vol% polystyrene with FAPbX2l.

[0007] In an embodiment, X is any one of Iodine (I) and Bromine (Br). In another embodiment, , X is Br.CAN DMS: \1007183365\3 1

[0008] In an embodiment, the film comprises a polymer, the polymer comprising at least one of polyvinylidene fluoride (PVDF) and copolymers of PVDF. In another embodiment, a p phase of the at least one of polyvinylidene fluoride (PVDF) and copolymers of PVDF is in a range of 36% to 71.5%.

[0009] In an embodiment, the film has a Young’s modulus between to 1 .3 GPa and 1.16 GPa.

[0010] In an embodiment, the film has a dielectric permittivity of greater than 28. In another embodiment, the dielectric permittivity is about 38.

[0011] In an embodiment, the film is poled with at least +5V de bias. In another embodiment, the film is poled with at least + 10V de bias for at least 10 minutes.

[0012] Embodiments may include combinations of the above features.

[0013] In another aspect, the disclosure describes a piezoelectric nanogenerator comprising the film according to this disclosure.

[0014] In an embodiment, the piezoelectric nanogenerator comprises a layer of the film according to this disclosure positioned between a first electrode and a second electrode.

[0015] In an embodiment, wherein the film has a thickness of between 58 and 65 pm.

[0016] In an embodiment, the piezoelectric nanogenerator has an output current density in a range of 2.6-25 pAcnr2N-1.

[0017] In an embodiment, the piezoelectric nanogenerator has an output current density greater than 25 pAcnr2N’1.

[0018] In an embodiment, the piezoelectric nanogenerator has breakdown strength of greater than 150 Vprrr1. In another embodiment, the piezoelectric nanogenerator has breakdown strength of about 191 Vprrr1.

[0019] Embodiments may include combinations of the above features.

[0020] In a further aspect, the disclosure describes a cascade piezoelectric nanogenerator (CPENG) comprising the a plurality of layers, each of the plurality of layers comprising a film according to this disclosure.

[0021] In an embodiment, the CPENG comprises a plurality of units, each unit having: a first layer of the plurality of layers comprising the film according to this disclosure positioned between2CAN DMS: \1007183365\3a first electrode and a second electrode, and a second layer of the plurality of layers is positioned adjacent to the second electrode, wherein the film of the first layer has an opposite polarization direction to the film of the second layer.

[0022] In an embodiment, the first layer defines a first positive polarization surface coupled by the first electrode to a second positive polarization surface of a first adjacent layer of the plurality of layers to create a positive terminal; and wherein the first adjacent layer defines a first negative polarization surface coupled by the second electrode to a second negative polarization surface of a second adjacent layer to form a negative terminal.

[0023] In an embodiment, the CPENG comprises 2-21 layers, wherein each layer is positioned between two electrodes.

[0024] In an embodiment, the first electrode, and the second electrode each comprise at least one of silver, gold, copper, and / or nickel. In anther embodiment, first electrode and the second electrode are copper.

[0025] In an embodiment, the CPENG comprises a urethane-based prepolymer coated on the first electrode, the second electrode, the film of the first layer, and the film of the second layer.

[0026] In an embodiment, the plurality of layers are defined between by a substrate.

[0027] In an embodiment, the CPENG has an output current density in a range of 2.6-25 pAcnr2N-1.

[0028] In an embodiment, the CPENG has an output current density greater than 25 pAcnr2N'1.

[0029] Embodiments may include combinations of the above features.

[0030] In a further aspect, the disclosure describes a method of making a piezoelectric composite film. The method comprises: preparing a first solution by adding a polymer to a first solvent; preparing a second solution by adding polystyrene, formamidinium iodide, and PbX2to a second solvent, where X is a halide; homogenously mixing the first solution with the second solution to create a mixture; and maintaining the mixture at a substantially constant temperature to crystalize the polymer and PS-FAPbX2l; casting the mixture of the crystalized polymer and PS-FAPbX2l onto a substrate to form at least one film.

[0031] In an embodiment, the first solvent and second solvent are N,N-Dimethylformamide (N, N DMF).3CAN DMS: \1007183365\3

[0032] In an embodiment, the polymer is at least one of PVDF and copolymers of PVDF, optionally 10 wt. % PVDF.

[0033] In an embodiment, the at least one film comprises 0.1-20 wt. / vol % PS-FAPbX2l.

[0034] In an embodiment, the film comprise 1 wt. / vol % PS-FAPbBr2l.

[0035] In an embodiment, X is Iodine (I) or Bromium (Br).

[0036] In an embodiment, the method comprises poling the at least one film with an electric field of 50-120 Vpnr1.

[0037] In an embodiment, the method comprises laminating a first film of the at least one film between a first electrode and a second electrode.

[0038] In an embodiment, the at least one film comprises a second film, and the method comprises: adhering the second film to the second electrode; and adhering a third electrode to the second film to form a cascade piezoelectric nanogenerator.

[0039] Embodiments may include combinations of the above features.

[0040] Further details of these and other aspects of the subject matter of this application will be apparent from the detailed description included below and the drawings.DESCRIPTION OF THE DRAWINGS

[0041] Reference is now made to the accompanying drawings, in which:

[0042] FIG. 1A shows schematic view an example Surface Functionalization of Organometal Halide Perovskite showing cation-TT interaction mechanism between FAPbB^I and polystyrene (PS).

[0043] FIG. 1 B is a graphical illustration of Raman spectroscopy of an example organometal halide perovskite according to this disclosure.

[0044] FIG. 1C is a graphical illustration of X-Ray Diffraction (XRD) patterns of the pristine formamidinium (FA) PbB^I- polyvinylidene fluoride (PVDF) (FAPbBr2l-PVDF) and 1% PS- FAPbBr2l-PVDF films.

[0045] FIGs. 1D and 1E are a graphical illustrations of Time of Flight - Secondary Ion Mass Spectrometry (ToF-SIMS) depth profiling of pristine FAPbB^I and PS-FAPbBr2l-PVDF films respectively.CAN DMS: \1007183365\3

[0046] FIG. 1 F is an Field Emission Scanning Electron Microscopy (FE-SEM) image of the grains of plain FAPbBr2l; FIG. 1G is a FE-SEM image of an example 1% PS functionalized FAPbBr2l thin film; and FIG. 1 H is an Atomic force microscopy (AFM) surface topography image of an 1% PS-FAPbBr2l film.

[0047] FIG. 2A is a schematic illustration of an Electric-field induced Ion-migration in an Organometal Halide Perovskite (OHP) FAPbBr2l-PVDF composite film showing the role of the Polystyrene. FIG. 2B is a graphical illustration of dark-current density of pristine and 1% PS FAPbBr2l-PVDF functionalized composites.

[0048] FIG. 3A is a graphical illustration kV Piezoelectric and dielectric response of t e OHP composite film; specifically, showing variation of electrical breakdown time of the pristine and 1% PS included composites of FAPbBr2l-PVDF with an applied electric bias of 3.

[0049] FIG. 3B is a graphical illustration of measured permittivity (er) of the composites of 3A.

[0050] FIG. 3C is a graphical illustration of output current density of the PENGs fabricated with varying PS concentration.

[0051] FIGs. D-F are 3-D graphical illustrations showing NanoScope Analysis 1.8 of the piezoelectric response in a 1 % PS-FAPbBr2l-PVDF film with different tip biases (area of 2x2 pm2).

[0052] FIG. 4A shows an example Cascade Piezoelectric Nanogenerator (CPENG) according to this disclosure. Each of the composites may be connected in parallel electrical connection. Two consecutive films have opposite polarization directions and are intercalated with a copper electrode. In the example, intercalated electrodes adjacent to the same polarization direction are connected.

[0053] FIG. 4B shows an image of a 21-layer CPENG and enlarged fragmented view by FE-SEM.

[0054] FIG. 5A-5D show graphical illustrations of performance of CPENGs. FIG. 5A shows measured output voltage; FIG. 5B shows current density of CPENGs made with 1 , 4, 8, 14, and 21 layers. FIGs. 5C and 5D show a comparison of experimental (FIG. 5C) and simulated (FIG. 5D) variations of output voltage and current density with total number of layers.

[0055] FIG. 6A is a schematic view of an example CPENG in an electrical circuit for energy storing to a capacitor.5CAN DMS: \1007183365\3

[0056] FIG. 6B is a graphical illustration of mechanical energy is converted to electrical energy by the CPENG to charge different capacitors.

[0057] FIG. 60 is a graphical illustration of an example CPENG charging an LTC 3588-2 system on a chip (SoC).

[0058] FIG. 6D is a is a graphical illustration of a comparison of normalized current density with CPENG and other representative PENGs.DETAILED DESCRIPTION

[0059] Before any embodiments are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0060] DEFINITIONS

[0061] Although terms such as “maximize”, “minimize” and “optimize” may be used in the present disclosure, it should be understood that such term may be used to refer to improvements, tuning and refinements which may not be strictly limited to maximal, minimal or optimal.

[0062] The term “connected” or "coupled to" may include both direct coupling (in which two elements that are coupled to each other and contact each other) and indirect coupling (in which at least one additional element is located between the two elements).

[0063] The term “substantially” as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related. For example, a drive shaft as disclosed herein having a circular transverse cross-section may permissibly have a somewhat non-circular cross-section within the scope of the invention if its rotational driving capability is not materially altered.

[0064] Terms such as "up to", "at least", "greater than", "less than", "more than", "or more", and the like, include the number recited and such terms refer to ranges that can be subsequently broken down into sub-ranges. In the same manner, all ratios recited herein also include all subratios falling within the broader ratio.6CAN DMS: \1007183365\3

[0065] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and / or" means any one of the items, any combination of the items, or all of the items with which this term is associated.

[0066] The term "about" can refer to a variation of± 5%, ± 10%, ± 20%, or± 25% of the value specified. For example, "about 50" percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term "about" can include one or two integers greater than and / or less than a recited integer at each end of the range. Unless indicated otherwise herein, the term "about" is intended to include values and ranges proximate to the recited range that are equivalent in terms of the functionality of the composition, or the embodiment.

[0067] Aspects of various embodiments are described through reference to the drawings.

[0068] FIG. 1A illustrates an example Organometal halide perovskite (OHP) according to this disclosure. Organometal halide perovskite (OHP) composites are remarkable in offering flexibility and easy synthesis and, hence play a pivotal role in ambient mechanical energy harvesting applications. Yet, the output current density from the OHP composite-based piezoelectric nanogenerators (PENGs) remains orders of magnitude lower than the ceramic-based piezoelectric composites, severely restricting their applications in harnessing ambient vibrations. Example PENGs are described in International Patent Application No. PCT / CA2021 / 050892, file on June 29, 2021 , the entire contents of which are hereby incorporated by reference. In some prior composites, markedly enhanced dielectric constant (er) arises from the inclusion of high permittivity nanoparticles, resulting in a trade-off between high erand low dielectric strength (Eb). This phenomenon led us to the design concept: increase dielectric constant by inclusion of the high er nanoparticle, while also enhancing the Eb by optimizing the perovskite structure. With this in mind, this disclosure describes OHP nanoparticles in which the surface has been chemically functionalized and greatly suppressed its electrically triggered ion migration to achieve both a higher erand E which results in a greater piezoelectric response. The delicate balance of polystyrene molecules (about 1 wt. / vol%) with FAPbBr2l enlarges the individual grains, homogenizes the halide ion distribution, and preserves their structural integrity within a polymer matrix. In an aspect, the resulting OHP piezocomposite in a PENG may produce an output current density of 2.6 pAcnr2N'1. To further increase the current density of OHP-based PENGs, multiple piezocomposites may be used to fabricate a cascade piezoelectric nanogenerator (CPENG). Intercalated electrodes in the 14-layer CPENG increase the overall surface polarization charges,7CAN DMS: \1007183365\3resulting in a large output current density that reaches up to 25 pAcnr2N’1. This is at least an order of magnitude enhancement for OHP-based PENGs, and higher than the record current density reported for any ceramic composites.

[0069] Piezoelectric nanogenerators use the piezoelectric effect for harnessing ambient vibrations to trickle charging modern electronic devices and sensing networks. Due to their unique merits in compact size, weight, and stability in harsh environments, PENGs are considered one of the most suitable energy harvesting technologies in recent years to be used with wearable, flexible, and implantable sensing platforms. Piezoceramics such as Pb(ZrTi)O3(PZT), BaTiO3(BTO), Pb (Zni / 3Nb2 / 3)O3-PbTiO3 (PZN-PT), Sm-Pb(Mgi / 3Nb2 / 3)O3-PbTiO3(Sm-PMN-PT) are the dominant materials of choice for PENG applications due to their large piezoelectric charge constants. Yet, their brittle nature and cost pose challenges in various applications. Consequently, flexible polymers like poly (vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-trifluoro ethylene) (PVDF-TrFE), polydimethylsiloxane (PDMS), etc. are used as host matrices in conjunction with piezoceramic fillers.

[0070] The successful utilization of PENG as an energy source hinges on attaining both sufficiently high voltage and current outputs. While the output voltage from PENG exceeds 3 V (sufficient for most charging applications), a significant challenge in addressing the charging needs of most electronic devices persists in their low output current densities. Diverse strategies have been implemented to boost current densities, including the exploration of innovative device structures and selection of materials with high piezoelectric charge constant (d33). For instance, by stacking PZT NW arrays Gu et al. (Reference 10) fabricated PENG with a current density of 23 pAcnr2in 2013, in 2014, Park et al. (Reference 11) developed PZT thin film-based PENG with interdigitated electrodes and reported a current density of 150 pAcrrr2. Materials with high piezoelectric charge constants to yield high output current density in a PENG while reducing the piezoelectric voltage coefficient (g33) and the output voltage according to the relation of (g33=d33 / er; £ris the relative permittivity). However, if the high d33ceramic material is dispersed in a high g33polymer matrix such as PVDF, PVDF-TrFE, it can yield a high output current density while retaining a standard output voltage level above 3 V. For instance, Sm-PMN-PT@PVDF piezoceramic composite has a current density of 15 pAcnr2(1.24 pAcnr2N'1), and a voltage of 7 V. In 2020, Gu et. al (Reference 7) marked another record of output current density to 290 pAcnr2(24 pAcrrr2N'1) by stacking 72-layers of Sm-PMN-PT@PVDF films, which is still the best- reported piezoceramic composite. The critical metric for assessing the PENG performance lies8CAN DMS: \1007183365\3in the normalized current density, denoted in pAcnr2N-1. This parameter considers the applied force necessary for the generation of the reported current, offering a comprehensive gauge of the device's operational efficiency.

[0071] Organometal halide perovskites (OHPs) have been used in PENG devices because they provide multiple advantages, including their solution processability, flexibility, and low- temperature synthesis when compared to traditional piezoceramics. These features enable the fabrication of OHP-based PENG devices on large-area flexible substrates, making them suitable for applications in flexible, wearable, and implantable electronics. Recent research has demonstrated that the piezoelectric charge constants (das) of OHPs are now comparable to those of piezoceramics, such as TMCM-MnCh (TMCM, tri-methylchloromethyl ammonium) (d33- 185 pCN’1), TMCM-CdCI3(d33~ 220 pCN’1), (TMFM)x(TMCM)i.x-CdCI3(TMFM, tri-methylfluoromethyl ammonium; 0 < x <1) (d33~ 1540 pCN'1), etc. Despite the use of high piezoelectric charge constant OHPs, the challenge of achieving high current density persists. For instance, the maximum current density for the TMCM-CdCI3@PDMS composite was reported as 3.45 pAcnr2(equivalent to 0.69 pAcm-2N-1).

[0072] Like piezoceramics, a prevalent strategy to improve the performance of OHP-based PENGs (and others) involves utilizing a matrix of piezoelectric polymers such as PVDF in combination with OHP nanomaterial. While this disclosure describes the use of PVDF in OHP- PENGs, other piezoelectric polymers may be used, e.g. co-polymers of PVDF such as at least one of P(VDF-trifluoroethylene), P(VDF-tetrafluoroethylene), P(VDF-tetrafluoroethylene). Poling in such composites induces the formation of the electroactive p-phase through electrostatic interaction with the nanomaterial. Despite achieving hundreds of volts in output voltage, the normalized current density of such PENGs remains notably low, with the highest reported value at 0.72 pAcm’2N’1. This figure is roughly 30 times lower than the best-performing PENGs utilizing piezoceramics. A challenge in such composites arises from the trade-off between achieving a high dielectric constant and their low dielectric strength. While a high dielectric constant enhances polarization (resulting in a higher piezoelectric charge constant), the lower dielectric strength limits the poling of these composites at sufficiently high electric fields for extended durations. Consequently, the unidirectional alignment of piezoelectric domains cannot be achieved, compromising optimal performance. In the case of OHPs, the breakdown is induced by ion migration effects under the applied poling electric field, leading to perovskite structure degradation. Grain boundaries play a critical role as preferred pathways for ion migration. Due to9CAN DMS: \1007183365\3the higher electrical conductivity of OHPs, they act as current pathways, and alterations to their structure, such as the formation of Pbl2or local p-n junctions, reduce conductivity and consequently, current density in the PENGs.

[0073] In an aspect, this disclosure provides a FAPbBr2l-PVDF-based PENG where polystyrene (PS) is employed to control the structure and compositional variation of FAPbBr2l. This ternary piezocomposite in a PENG may generate a high output current density of 11 Acrrr2(2.6 pAcnr2N-1). The piezocomposites may further be used as a building block to vertically assemble them. In an embodiment, multiple layers of piezocomposite films may be separated through intercalated electrodes to enhance the output current density. In an embodiment, the electrodes comprise any one of silver, gold, copper, and nickel. Cascade-type architecture, e.g a 14-layer CPENG, may exhibit an impressive output current density, e.g. approximately 105 pAcnr2(peak to peak) at 30 Hz and 4.2 N, with a corresponding normalized current density of 25 pAcnr2N'1. This performance may surpass OHP-based PENGs by an order of magnitude and may outperform the ceramic-based composites, as reported with a normalized current density of 24.17 pAcnr2N'1in a 72-layer PENG. In an aspect, the basis of this improvement is due to (1) The use of polystyrene leads to significantly improved grain size which reduces the density of grain boundaries, as a result, ion migration may be reduced by an order of magnitude compared to plain FAPbBr2l-PVDF. (2) With the use of polystyrene, a uniform distribution of halide ions (Br and F) is achieved in the composite, this leads to a homogenous band structure and prevents the formation of local energy barriers (due to variation in band structure from changes in halide composition) which could impede current collection. (3) The dielectric constant of the PS-FAPbBr2l-PVDF composite is improved by over 5 times compared to plain FAPbBr2l-PVDF, which will increase the piezoelectric charge constant. (4) X-ray diffraction results reveal increased lattice spacing with the use of polystyrene, indicating strain relaxation in the OHP structure. This may further reduce ion migration, improve carrier mobility, and lower defect concentration, contributing to the stabilization of the PENG devices and enhancing charge collection. These effects collectively may contribute to a higher breakdown strength in PS-FAPbBr2l-PVDF-based PENGs, which may, in an example, sustain up to 30 minutes of poling at a field strength of ~ 50 Vpnr1compared to plain FAPbBr2l- PVDF devices that typically breakdown in less than 1 minute under similar conditions. Thus, aspect of this disclosure demonstrate mitigation of challenges associated with OHP-based piezoelectric nanogenerators through a synergistic approach involving optimized material design10CAN DMS: \1007183365\3and effective device engineering by cascading multiple layers leading to improved record- normalized current densities.

[0074] In an aspect, a method of making polymer functionalized perovskite composites is provided. In an embodiment, polystyrene is used to functionalize the OHP (FAPbBr2l) because of its specific interactions with, the A site cation (FA+) and the lead halide species. Additionally, its high dielectric strength along with low dielectric losses, makes it particularly advantageous for PENG applications. Integrating polystyrene into the perovskite matrix results in the modulation of both nucleation and the growth rate of perovskite crystal grains, accompanied by a reduction in defect density. The functionalization is grounded in the typical cation-TT interaction between the FA+cation of the FAPbBr2! and TT -electrons of aromatic styrene in polystyrene as illustrated in Fig. 1A. The specific molecular-level interaction between perovskite precursor and polystyrene was characterized by Raman spectroscopy which showed that the pristine FAPbBr2l-PVDF and PS-FAPbBr2l-PVDF films exhibit sharp characteristic peaks of Pb-X (X=l, Br) lattice mode centered at 80 cm'1and a broad peak (160-250 cm'1) corresponding to the organic moiety. As observed in Fig. 1 B, adding 1 wt. / vol% PS in the FAPbBr2l, the peak corresponding to the Pb-X (X=l, Br) lattice mode shifts to a lower wavenumber. Such variation in the Raman active modes of the perovskite signifies an enhanced molecular-level interaction between polystyrene and perovskite precursors. Similar interaction between polystyrene and the organometal halide perovskite precursors has been previously confirmed by gel permeation chromatography and the growth of single crystal perovskite. The X-ray diffraction pattern in Fig. 1C shows the presence of the dominant peaks corresponding to (001) (002) and (210) lattice planes and highlights the formation of the mixed halide perovskite phase in both pristine FAPbBr2l-PVDF and PS-FAPbBr2l- PVDF films. A stronger anisotropic orientation along the (001) plane is evident in pristine FAPbBr2l compared to PS-FAPbBr2l. From the view of thermodynamics, orientation diversity offers increased entropy and a more stable perovskite phase. The narrowing of the peak (reduction in the full width and half maximum value) and increase in the peak intensity in the PS- FAPbBr2l-PVDF XRD pattern indicates improved crystallinity and an increase in the crystallite size. An additional shoulder peak of residual PbX2(X=l, Br) is observed at 20 of 12.4° exclusively in the pristine FAPbBr2l. The absence of the PbX2(X=l, Br) peak in the PS-perovskite composite film can be ascribed to the ability of polystyrene chains to interact with Pbh and PbBr2, which are weak Lewis acids and formed intermittently during solvation of perovskite precursors. This leads to enhanced perovskite phase conversion from the combined interaction between polystyrene11CAN DMS: \1007183365\3(PS), Formamidinium (FA), and PbX2. Additionally, there is a consistent shift in the XRD peaks toward lower 20 values in PS-FAPbBr2l-PVDF films compared to FAPbBr2l-PVDF films. This shift indicates a lattice expansion in the PS-FAPbBr2l-PVDF films, signifying relaxation in the perovskite lattice.

[0075] Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) depth profiling was conducted, shown in Figs. 1 D and 1 E, to see the variation in the distribution of the halide ions between PS-FAPbBr2l-PVDF and FAPbB^I -PVDF films. It was observed that a uniform concentration of |- and Br is present across the PS-FAPbBr2l-PVDF composite film. In comparison, for the FAPbBr2l-PVDF film, the |- distribution is lower and non-uniform (especially during the initial 0-200 sec of sputtering) relative to the Br profile, hence showing phase segregation in the top layer. Phase segregation of the halide ions can lead to detrimental effects on the device's performance due to structural changes. In the perovskite solution system, the atoms, ions, and solvent molecules can coordinate with each other, forming intermediate adducts or complexes. Since the trend of Lewis acidity in lead (II) halide follows the order of Pbl2>PbBr2, the stronger interaction of Pbl2 with polystyrene allows more iodide-rich perovskite phase formation which leads to its uniform distribution across the film. This observation combined with the shift of the peak position in the X-ray diffraction patterns for PS-FAPbBr2l-PVDF, confirms that the perovskite lattice is larger due to the uniform inclusion of the higher ionic radii of the 6- coordinated |- (rl - 2.06 A) along with Br (rBr = 1.82 A). The larger lattice will also have a smaller strain which has been shown to improve the stability of the perovskite phase, along with decreased defect density and increased carrier mobility. The depth profiling data also reveals that the signal intensity of the |- ion is maintained at the same level as that of the F- ion (representative of PVDF) across the entire depth of the sputtering time, shown in Fig. 1 D, in the PS-FAPbBr2l'PVDF film. This shows that the composite is homogenous and the interaction between PVDF and the perovskite phase will be uniform across the film.

[0076] The direct interaction of polystyrene chains with the perovskite precursors leads to relatively larger grain size in the PS-FAPbBr2l films in comparison to that of pristine FAPbB^I as evident in the lateral field emission scanning electron microscopy images, shown in Figs. 1 F and 1G. Due to the decreased nucleation rate, average grain sizes increase from 400-600 nm (in FAPbBr2l) to 600-900 nm in the PS-FAPbBr2l film. AFM surface topology, shown in Fig. 1 H, also confirms the large grain formation on the PS functionalized film. Therefore, it is expected, based12CAN DMS: \1007183365\3on these combined effects, greater stability of the perovskite phase in the PS-FAPbBr2l-PVDF films is expected, along with lower ion migration effects.

[0077] Dielectric and piezoelectric properties of piezocomposite of this disclosure were analyzed. An electric field was applied across the composite film to align the dipoles unidirectionally to generate a macroscopic dipole moment. The electric field applied for a sufficiently longer time causes 60 / 180° rotation of the molecular chains and a conversion of the a to the p- phase even without the mechanical stretching of the chains. The most widely used PVDF polymer requires a high electric field of at least 50 Vpnr1to completely harness its piezoelectric capabilities. Such a requirement imposes serious restrictions in manipulating OHP composites, as a high electric field proliferates dynamic point defects and causes faster breakdown due to ion migration as illustrated in Fig. 2A. In an OHP perovskite structure, FA+, Br / k and Pb2+are all considered mobile ions, and this results in high ionic conductivity, and a large leakage current in the perovskite-based devices. In this disclosure, it was found that, with an external bias in the dark, an electronic current is instantly observed owing to the fast movement of the electronic charge carriers. At the same time, the mobile ions with low activation energy also slowly drift toward metal electrodes. As the oppositely charged ions begin accumulating at the metal electrodes, the ion-induced electric field partially cancels the external bias and reduces the overall current. This transient decay in current is observed until the ion accumulation reaches an equilibrium condition, shown in Fig. 2B. The pristine FAPbB^I film owing to the higher density of mobile ionic defects and halide ion segregation may exhibit a large decay in the current. As shown in Fig. 2B, the dark current in the pristine FAPbB^I film decays rapidly from its initial value of 3.10x10-6 mA / cm2and reaches 1.86x10-6 mA / cm2(~ 40% decay) within 35 sec. In contrast, the PS-FAPbBr2l films exhibit a much lower dark current (~ 5.0x10-7 mA / cm2) which decays by a smaller magnitude to ~ 4.20x10-7 mA / cm2. The smaller magnitude of decay in the dark current implies that the polystyrene reduces the ion migration effect by more than an order of magnitude, based on the structural results discussed above. Furthermore, the electric field strength-dependent leakage current density of pure FAPbBr2l-PVDF based devices was observed to be 5.44x10-4 mA / cm2at 0.1 kV / cm and 1.49x10-2 mA / cm2at 3 kV / cm. In contrast, the leakage currents in the 1 wt.% PS- FAPbBr2l-PVDF composite films is reduced to 1.67x10-5 and 1.35x10-3 mA / cm2, respectively, at the same electric fields. The multiple-fold reduction in the leakage current in the presence of polystyrene further corroborates its beneficial role in providing insulation against the leakage13CAN DMS: \1007183365\3paths in the composite film while simultaneously allowing improved grain growth and homogenized distribution of FAPbB^I nanoparticles across the PVDF matrix.

[0078] The structural integrity of the OHP perovskite in the composite may be crucial to preventing undesirable breakdown during poling. In this disclosure, a comparison of the average dielectric strength of 12 different locations on each of the composite devices was undertaken. The 1% polystyrene devices had an average breakdown strength of 191 Vpm-1 , 130% times that of the films without polysytrene. Based on the average poling electric field of composites being between 40-120 Vpm-1 , a de bias of 3 kV was applied to the pristine (without any polystyrene) and 1 % polystyrene containing composites, having a thickness of ~ 65 pm, and ~ 58 pm, and noted the breakdown time shown in Fig. 3A. With the electric field of ~ 46 Vpm-1 , all the pristine films reached their breakdown point in less than 5 minutes, while 50% of them could withstand only 1 minute of poling. In contrast, the polystyrene (PS)-containing composites could survive up to 30 minutes of poling with an electric field of ~ 51 Vpm-1 , where the lowest- performing devices have a breakdown point higher than all the pristine composite samples.

[0079] A striking difference was observed in the relative dielectric permittivity (er) of the plain and polystyrene functionalized composite films. In contrast to the erof 7.5 in pristine FAPbB^I, the 1% polystyrene functionalized films exhibit a ervalue of 38 (Fig. 3B), representing an increase of more than 5 times. The more homogeneous distribution of perovskite species and improved crystallinity with larger grain size are anticipated to increase the dielectric constant of 1 % PS composites. Since grain boundaries typically have smaller dielectric permittivity than the grains in perovskite materials. The observed peak shift to smaller angles in the XRD data suggests a relaxation in the perovskite lattice. It is expected that the relaxation may enhance dipole alignment and polarizability.

[0080] The polystyrene concentration was varied to observe its influence on the output current generation in the PENG devices. The output current density from the PENG devices improved especially for the 1% polystyrene containing FAPbB^I film which has the highest current density of 11 pA / cm2. This is 2.4 times higher than the pristine perovskite PENGs, and 7.3 times higher than pristine PVDF-based devices as shown in Fig. 3C. This is attributed to the structural effects which include larger grain size, defect passivation of perovskites, and enhanced dielectric constant with a more homogenous composition of the composite. The interaction between PS- FAPbBr2l and PVDF was studied from the absorbance spectra of pure polystyrene, pure PVDF,14CAN DMS: \1007183365\3PVDF-PS and PVDF-PS-FAPbBr2l films. In the FTIR spectra, the characteristic peaks of polystyrene appear at 696 cm-1(aromatic ring bending), 1492 cm-1(aromatic ring mode), 2850 and 2923 cm-1(CH2 symmetric and asymmetric stretching), and 3025, 3059 and 3081 cm’1(aromatic C-H stretching). Similarly, distinctive peaks of PVDF centered at 487 cm'1(CF2bending and wagging), 613 cm'1(CF2bending and CCC skeletal vibration), 763 cm'1(CH2and CF2inplane rocking or bending), 875 cm'1(CC symmetric stretching and skeletal bending) and 1184 erm1(CF2stretching) are observed.

[0081] In the PVDF-PS film, the characteristics peaks for PVDF show no change which indicates little interaction between PS and PVDF. The intensity of PS-related peaks is reduced due to its relative small concentration (1 wt. %). In the PS-FAPbBr2l-PVDF film, while the peaks observed in the PVDF-PS film are retained, a new peak corresponding to the CN stretching in the formamidinium group of perovskite appears at 1715 cm-1. Furthermore, the IR peak corresponding to CC stretching in PVDF shifts from 875 cm'1to a higher wavenumber of 880 erm1indicating interaction with the perovskite. In an aspect, a notable feature is that with PS-OHP in the PVDF matrix, the p-phase content in PVDF increases from 36% to 71.5%. This is based on the diminishing of the a-phase PVDF peaks at 614, 763 and 974 cm'1in the PS-PVDF-Perovskite film. An enhancement in the relative intensity of the IR peaks at 840 and 1276 cm'1is observed which correspond exclusively to the p-phase of PVDF. Nevertheless, at higher PS concentrations, effective perovskite content reduces in the film, and this decreases the overall film quality and the effective beta-phase amount in the PVDF. So, a decreasing trend in output current density with larger polystyrene loading is observed. The output voltage from the 0% PS film is slightly lower than the 1% polystyrene film, while PS loading beyond 1% may further decreases the output voltage. To assess its flexibility, Young’s modulus (YM) of the composites with different polystyrene additions was also measured from the tensile stress-strain curves. The Young’s modulus was calculated for the 0% PS film as 1.35 GPa, while for the 1% and 10% PS-added films it was reduced to 1.3 GPa and 1.16 GPa. Thus, obtaining a delicate balance with the amount of polystyrene in the composite is critical. The microscopic piezoelectric response was measured with the applied electric bias (+5 V, +10 V) in a piezoelectric force microscopy (PFM), shown in Figs. 3D, 3E, and 3F). The 1 % PS composite film poled with +5 V de bias for ~ 10 minutes exhibits an amplitude response of ~ 1 .5 V, which is ~ 10 times more than the non-poled film (0 V). As the de bias was increased to +10 V for 10 minutes, amplitude response further increased to ~ 1.8 V. It was evident that with the rise in electrical poling voltage and poling time, more and more dipoles15CAN DMS: \1007183365\3are unidirectionally aligned and resulting in a higher piezoelectric response in the composite film. This experiment further depicts the importance of electrical poling of the composite film for obtaining an enhanced piezoelectric response.

[0082] In an aspect, a CPENG is provided according to this disclosure. FIG. 4A shows an example CPENG 400. The enhanced current density and stability observed in the 1% polystyrene composites served as motivation to adopt it as a foundational element for the assembly of the multilayer Cascade Piezoelectric Nanogenerator (CPENG). In a PENG, the piezoelectric polarization charges are utilized to produce output current to the external circuit. When subjected to mechanical stress, opposite polarization charges emerge at the interfaces of the top and bottom electrodes. The prospect of creating numerous interfaces through two-dimensional electrodes within a piezoelectric film holds the potential for a substantial enhancement in output current density. To achieve a cascade device, intercalated electrodes 401 , .e.g. copper electrodes were positioned between two oppositely poled composite films 402a, 402b as shown in Fig. 4A. Electrodes 401 were interconnected in a parallel electrical configuration. In an emboidment, the electrodes may be any one of silver, gold, copper, and nickel. In an embodiment, positive polarization surfaces 403 are linked to create a common positive (+ve) terminal, and the negative surfaces 404 of the films 402a, 402b formed a shared negative (-ve) terminal. When subjected to force, the current generated in each unit 405 accumulated through the interfacial electrodes 401 , result in a larger combined current output. In an example, a solvent-free urethane-based prepolymer 406 may be employed as an adhesive owing to its initial adhesion, workability, and bonding capacity. The adhesive was blend-coated on an electrode and tightly pressed with the composite film for a time period, e.g. 48-72 hours, in ambient conditions. Subsequently, another composite film according to this disclosure with opposite polarity was coated with the adhesive and securely bonded to the copper electrode, forming a single electrode intercalated 2-layer PENG device. This process was repeated to fabricate example CPENGs with e.g. 1 , 4, 8, 14, and 21 layers. Fig. 4B presents a photograph of a CPENG with 21 layers, accompanied by an enlarged fragmentary view of cross-sectional scanning electron microscopy images. A homogeneous distribution of perovskite nanoparticles within the piezocomposite was provided and well-intercalated copper electrodes between the composite films.

[0083] A mechanistic investigation was conducted using finite element analysis to understand how the assembly of multiple layers could optimize the output performance. The piezo potential of various models was simulated with 1 , 4, 8, 14, and 21 layers of films, maintaining opposite16CAN DMS: \1007183365\3polarization directions for two consecutive films. With an increase in the number of layers, the piezo potential decreases from 30 V (single layer) to 3 V for a 21-layer PENG. When a force is applied to the PENG, the dipole moments become smaller along the thickness direction, leading to the cancellation of the piezo potential due to the opposite polarization direction of two consecutive films. However, the change in polarization across each layer translates to output current, which is then multiplied through intercalated electrodes.

[0084] Output performance and application of the CPENG was analyzed. To assess the practical mechanical energy harvesting capabilities of the devices, a force of 4.2 N (0.42 kg) was applied using a steel block and systematically examined their respective performance. The single-layer PENG produced a maximum output voltage of approximately 29 V. This voltage gradually decreased to 17 V, 7 V, 3.5 V, and 2.6 V for the 4, 8, 14, and 21-layer devices, respectively as shown in Fig. 5A. This behaviour may be elucidated through the simple capacitor model, wherein the parallel connection of capacitors leads to an increase in overall capacitance, subsequently causing a decrease in voltage (V=Q / C; V=voltage, Q=charge, C=capacitance).

[0085] The output current density of the devices was measured under short-circuit conditions, as illustrated in Fig. 5B. As the number of layers increased to 1 , 4, 8, 14, and 21 , the output current density rose from 11 pA / cm2 to 29 pA / cm2, 64 pA / cm2, 105 pA / cm2, and then decreased to 55 pA / cm2, respectively. Fig. 5C demonstrates that while the output voltage decreases nonlinearly, the output current density increases almost linearly with the number of layers. Moreover, the finite element simulation model reveals that the calculated total charge density in short-circuit conditions (which corresponds to current density) follows a similar increasing trend with the number of layers in a PENG, as depicted in Fig. 5D. The simulation results in Fig. 5D align with our experimental findings, except for the current density for the 21-layer CPENG. It is hypothesized that this is due to the strong stress- buffering effect as the number of layers increases. The use of a higher number of copper / adhesive electrodes may reduce the transmitted stress to each composite, which was not included in the simulation model.

[0086] The CPENG demonstrated resilience during testing for ~ 1000 mechanical cycles without deterioration in its performance. To validate its practical energy harvesting capabilities, the CPENG 400 was connected through a full bridge rectifier 600 to different capacitors 601 as shown in Fig. 6A. As shown in FIG. 6B, the CPENG was used to charge different capacitors of 4.7 pF,17CAN DMS: \1007183365\310 pF, 22 pF, and 47 pF. At 30 Hz and 4.2, N it can charge a 4.7 pF capacitor to ~ 1 V in 16 s, 10 pF to 1 V in 38 s, 22 pF to 0.95 V in 50 s, and 47 pF to 0.6 V in 1 min.

[0087] Gently triggering the CPENG with a finger generated and stored electricity, with 24 touches charging a 1 pF capacitor to 0.8 V, showcasing a high charging rate for a PENG at low frequency. Additionally, the CPENG (4 layers) powered a System on Chip (SoC) at 30 Hz (Fig. 6C), enabling it to activate an example radio frequency (RF) transmitter module embedded in the SoC every 2 minutes. PENG and CPENGs according to this disclosure may be scaled up for other practical applications. In an example, the output current density of the 14-layer CPENG was normalized with the applied force of 4.2 N and compared it with state-of-the-art PENGs as shown in Fig. 6D. The output current density per unit force in the CPENG is notably higher, surpassing the reported OHP-based PENGs by an order of magnitude. Among ceramic-based composites, the 72-layer PENG holds the highest reported normalized current density of 24.17 pAcnr2N'1. In contrast, the 14-layer CPENG in this study, with PS-FAPbBr2l composites, generates 25 pAcnr2N'1. In summary, the approach of functionalizing organometal halide perovskite with polystyrene has been employed to enhance the output current density of the piezoelectric nanogenerator. The optimization of polystyrene concentration in FAPbB^I precursors has been instrumental in reducing defects, increasing grain size, and achieving a more homogeneous distribution of halide ions, resulting in a smaller lattice strain. Consequently, the polystyrene-functionalized organometal halide perovskite (PS-OHP) exhibits greater structural integrity, reducing ion migration under an electric field and overcoming the 'dielectric constant vs. dielectric strength' limit. The optimized concentration of 1 % polystyrene significantly suppresses leakage current by one order of magnitude, demonstrating effective control over ion migration. Additionally, the controlled nucleation of perovskites through polystyrene incorporation leads to a twofold increase in grain sizes compared to pristine perovskites. The ternary composite design and cascading may helps to elevate the output current density of the extensively studied perovskite PENG by one order of magnitude. The high-performance PENG with ultrahigh current density achieved in this study may provide a sustainable power source for portable and flexible electronics.

[0088] EXAMPLES

[0089] Example 118CAN DMS: \1007183365\3

[0090] Methods of making pristine and PS-FAPbBr2l precursor solution are described. The FAPbBr2l precursor solution was prepared by dissolving an equimolar ratio (0.5: 0.5) of FAI (formamidinium iodide > 99%, Sigma-Aldrich) and PbBr2 (lead(ii) bromide > 98%, Sigma- Aldrich) in an N, N-DMF (N, N-dimethylformamide > 99%, Sigma-Aldrich) solvent, followed by stirring at 60 °C for 12 hours. To prepare PS-FAPbBr2l precursor solutions of varying concentration (1 , 5, 10, and 20 wt. / vol%), a corresponding amount of polystryene (average Mw 35 kDa, Sigma- Aldrich) was added to the perovskite precursor solution and stirred for 30 min.

[0091] Example 2

[0092] Method of making the PS-FAPbBr2l-PVDF composites are described. The PVDF solution was dissolved in N,N-Dimethylformamide (N, N DMF) with constant stirring at 50 °C for 24 hours. The final concentration of the PVDF in DMF was kept at 10 wt. %. Then, the PS-FAPbBr2l-PVDF composite precursor solutions were prepared by homogeneously mixing 1 wt. / vol % PS-FAPbBr2l and 10 wt. % PVDF. To optimize the concentration, the 1 , 10, and 20 wt. / vol% composite solutions were synthesized. Then the mixed solution was drop-cast onto a glass substrate and stored for approximately 1 hour for the degassing process, immediately followed by annealing at 120 °C. Highly crystalline composite films were obtained after 2 hours. Distributed nanoparticles with an average diameter of 15-20 nm inside the PVDF matrix were estimated by the high-resolution TEM image. To align the dipoles in the PS-FAPbBr2l- PVDF film, high-voltage electrical poling was completed with an electric field of 50-120 Vpnr1for 2-3 hours. After poling, the films were sandwiched between two copper electrodes. To prepare the electrodes, commercially available copper foil sheets with a thickness and resistance of 2.5 pm, and 0.05 Q / cm2were used. The copper sheets were cleaned with acetone, isopropanol, and deionized water to remove any adhesives on them. Then the prepared copper sheets were dried with nitrogen and cut into small sizes (1 cm x 0.45 cm) for use in the PENGs. Finally, the sandwiched structure of the polyester / copper / PS-FAPbBr2l-PVDF / copper / polyester film was pressed through thermal lamination, which eliminates air gaps and provides uniform adhesion between the copper electrodes and the piezoelectric film. Before poling, output current density was measured as 0.51 pA.cm-2, compared to 11 pA.cm-2 after the poling. When the terminals of the poled PENG were switched, the measured output current density signal also switched, indicating the signal is originating from the inherent piezoelectricity of the composite film.

[0093] Example 319CAN DMS: \1007183365\3

[0094] Methods of making multilayer assembly of the PS-FAPbBr2l-PVDF composites are described.

[0095] Each of the poled composite films was cut into 1.3 cm x 0.6 cm dimensions. Solvent-free urethane- based prepolymer was used as an adhesive between the electrode and the composite film. First, a few drops of the urethane prepolymer were poured on the copper electrode and spread with a glass rod to achieve uniformity. Second, the composite film was pressed tightly on the copper for adhesion. Third, another copper electrode was attached to the top of the composite film by using step one. Fourth, a few drops of urethane prepolymer were poured on another composite film and spread uniformly with a glass rod. Fifth, the composite film was pressed tightly on the copper electrode of step 3. Sixth, step 1 was repeated to grow the top copper electrode. In this way, two units of the composite films were cascaded. Then, steps 4, 5, and 6 were repeated to assemble 14 different layers. The polarity (polarization direction) of the composite films was determined by the electrical poling direction. Between two consecutive films, opposite polarity was maintained. Electrodes at the positive interfaces were shorted to make a single positive terminal, and similarly, electrodes of the negative interfaces were shorted to make a single negative terminal for the electrical measurements. The fabricated device can be bent by using a metallic tweezer, however, the performance of the CPENG may decrease in its bending operation mode. Finally, the device was packaged in between thermal laminating pouches.

[0096] Example 3

[0097] Methods of structural, microscopic, and spectroscopic characterization are described.

[0098] The X-ray diffraction characterization was carried out on the PANalytical Empyrean diffractometer with Cu Ka radiation (A = 1.54 A). A Zeiss Ultraplus field emission scanning electron microscopy (FE-SEM) was utilized for visualizing the surface topology and grain size distribution of the pristine and polymer-integrated perovskite films. The Raman spectroscopy for all films was performed using a Horiba HR800 spectrometer at an excitation wavelength of 532 nm and 6 mW power in the backscattering configuration. The time-of-flight second ion mass spectroscopy (ToF-SIMS) was performed to analyze depth profiling of freshly prepared perovskite and polymer-perovskite films using Cs+ion source (500 eV) for sputtering and Bi3+(30 keV) for analysis over ToF-SIMS, ION-TOF GmbH. Transmission electron microscopy (TEM) was recorded by using a Hitachi HT7700 transmission electron microscope with an acceleration20CAN DMS: \1007183365\3voltage of about 100 kV. FTIR absorbance spectra were collected by using Nicolet iS50 (Thermo Fisher Scientific).

[0099] Example 4

[0100] Methods of dielectric measurements are described.

[0101] The dielectric constant was measured by using a Keithley-4200 semiconductor parameter analyzer. An ac bias voltage of 100 mV was applied, while the frequency was swept from 0 to 1 MHz. The capacitances were measured by using parallel plate capacitor model approximation to calculate the dielectric constant. Dielectric strength was measured by applying voltage from a high-voltage de source on the top copper electrodes of the composite films. The applied voltage was increased with a step size of 500 V. All the experiments were conducted in the ambience.

[0102] Example 4

[0103] Methods of electrical and mechanical measurements are described.

[0104] The dark current measurement on the planar vertical device configuration was conducted using a probing station in a two-probe mode. A Keysight 6614C 50-watt system power supply was used for applying an external bias and the current was measured using a Keysight 3458A Digital multimeter. The perovskite film was connected in series with the multimeter and power supply to complete the circuit. Piezoelectric force microscopy was conducted by a Bruker AFM (Dimension Icon) in a vertical PFM mode. The probe used for the PFM was a n-doped (antimony) silicon coated with reflecting platinum (Pt) / iridium (Ir) on the back and had a nominal stiffness of 3 N / m. Data analysis including 3-D representations of the PFM images was performed by using NanoScope Analysis 1.8. To study the electrical output performance of the PENGs an electrodynamic shaker (Lab Works Inc.) was used, controlled by a power amplifier and a controller. A digital oscilloscope (Tektronix 2004 C) and a low-noise current preamplifier (SR 570, Stanford Research Systems Inc.) were used to measure the electrical signal output from the nanogenerators. A 10X signal cable was used to collect the voltage signals from the PENGs. Young’s modulus (YM) of the composite films was measured from the tensile stress-strain curves obtained by an Instron 5548 micro tester.

[0105] Alternate embodiments

[0106] The above description is meant to be exemplary only, and one skilled in the relevant arts will recognize that changes may be made to the embodiments described without departing from21CAN DMS: \1007183365\3the scope of the invention disclosed. The present disclosure may be embodied in other specific forms without departing from the subject matter of the claims. The present disclosure is intended to cover and embrace all suitable changes in technology. Modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims. Also, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

[0107] As can be understood, the detailed embodiments described above and illustrated are intended to be examples only. The invention is defined by the appended claims.

[0108] The claims are not intended to include, and should not be interpreted to include, means- plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively.

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Claims

WHAT IS CLAIMED IS:

1. A piezoelectric composite film comprising an organometal halide perovskite (OHP), the OHP comprising FAPbX2l and polystyrene, where X is a halide, preferably X is Bromine (Br).

2. The film of claim 1, wherein the OHP comprises about 0.1-20 wt% / vol% polystyrene with FAPbX2l.

3. The film of claim 1 or claim 2, wherein the OHP comprises about 1 wt% / vol% polystyrene with FAPbX2l.

4. The film of any one of claims 1-3, wherein X is any one of Iodine (I) and Bromine (Br).

5. The film of claim 4, where X is Br.

6. The film of any one of claims 1-5, comprising a polymer, the polymer comprising at least one of polyvinylidene fluoride (PVDF) and copolymers of PVDF.

7. The film of claims 6, comprising a phase of the at least one of polyvinylidene fluoride (PVDF) and copolymers of PVDF is in a range of 36% to 71.5%.

8. The film of any one of claims 1-7, having a Young’s modulus between to 1.3 GPa and 1.16 GPa.

9. The film of any one of claims 1-8, having a dielectric permittivity of greater than 28.

10. The film of claim 9, wherein the dielectric permittivity is about 38.

11. The film of any one of claims 1-10 poled with at least +5V de bias.

12. The film of claim 11, wherein the film is poled with at least +10V de bias for at least 10 minutes.

13. A piezoelectric nanogenerator comprising the film of any one of claims 1-12.

14. The piezoelectric nanogenerator of claim 13 comprising a layer of the film of any one of claims 1-12 positioned between a first electrode and a second electrode.

15. The piezoelectric nanogenerator of any one of claims 13-14 wherein the film has a thickness of between 58 and 65 pm.

16. The piezoelectric nanogenerator of any one of claims 13-15 having an output current density in a range of 2.6-25 pAcnr2N-1.27CAN DMS: \1007183365\317. The piezoelectric nanogenerator of any one of claims 13-16 having an output current density greater than 25 Acnr2N-1.

18. The piezoelectric nanogenerator of any one of claims 13-17 having breakdown strength of greater than 150 V rrr1.

19. The piezoelectric nanogenerator of claim 18 having breakdown strength of about 191 V rrr 120. A cascade piezoelectric nanogenerator (CPENG) comprising the a plurality of layers, each of the plurality of layers comprising the film of any one of claims 1-12.21 . The CPENG of claim 20 comprising a plurality of units, each unit having: a first layer of the plurality of layers comprises the film of any one of claims 1-12 positioned between a first electrode and a second electrode, and a second layer of the plurality of layers is positioned adjacent to the second electrode, wherein the film of the first layer has an opposite polarization direction to the film of the second layer.

22. The CPENG of any one of claims 21 , wherein the first layer defines a first positive polarization surface coupled by the first electrode to a second positive polarization surface of a first adjacent layer of the plurality of layers to create a positive terminal; and wherein the first adjacent layer defines a first negative polarization surface coupled by the second electrode to a second negative polarization surface of a second adjacent layer to form a negative terminal.

23. The CPENG of claim 21 or claim 22, comprises 2-21 layers, wherein each layer is positioned between two electrodes.

24. The CPENG of any one of claims 21-23, wherein the first electrode, and the second electrode each comprise at least one of silver, gold, copper, and / or nickel.

25. The CPENG of claim 24 wherein the first electrode and the second electrode are copper.

26. The CPENG of any one of claims claim 21-25, comprising a urethane-based prepolymer coated on the first electrode, the second electrode, the film of the first layer, and the film of the second layer.

27. The CPENG of any one of claims claim 20 -26, wherein the plurality of layers are defined between by a substrate.28CAN DMS: \1007183365\328. The CPENG of any one of claims 20-27 having an output current density in a range of 2.6- 25 pAcm-2N-1.

29. The CPENG of claim 28 having an output current density greater than 25 Acnr2N-1.

30. A method of making a piezoelectric composite film, the method comprising: a. preparing a first solution by adding a polymer to a first solvent; b. preparing a second solution by adding polystyrene, formamidinium iodide, and PbX2 to a second solvent, where X is a halide; c. homogenously mixing the first solution with the second solution to create a mixture; and d. maintaining the mixture at a substantially constant temperature to crystalize the polymer and PS-FAPbX2l; e. casting the mixture of the crystalized polymer and PS-FAPbX2l onto a substrate to form at least one film.

31. The method of claim 30, wherein the first solvent and second solvent are N,N- Dimethylformamide (N, N DMF).

32. The method of any one of claims 30-31 , wherein the polymer is at least one of PVDF and copolymers of PVDF, optionally 10 wt. % PVDF.

33. The method of any one of claims 30-32, wherein the at least one film comprises 0.1-20 wt. / vol % PS-FAPbX2l.

34. The method of claim 33, wherein the film comprise 1 wt. / vol % PS-FAPbBr2l.

35. The method of any one of claims 30-34, wherein X is Iodine (I) or Bromium (Br).

36. The method of any one of claims 30-36, comprising poling the at least one film with an electric field of 50-120 V rrr1.

37. The method of any one of claims 30-36, comprising laminating a first film of the at least one film between a first electrode and a second electrode.29CAN DMS: \1007183365\338. The method of claim 37, wherein the at least one film comprises a second film, and the method comprises: adhering the second film to the second electrode; and adhering a third electrode to the second film to form a cascade piezoelectric nanogenerator.CAN DMS: \1007183365\3

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