Polymer dielectrics particle inclusions in capacitors

Abstract

Composite dielectrics for capacitors, the capacitors themselves, and method of manufacturing the same. The composite dielectrics disclosed have solid particle and molecular inclusions in the composite dielectrics. An exemplary composite dielectric can include a polymer dielectric and a particle additive distributed substantially uniformly in the polymer dielectric, where the particle additive is in a relative amount of between 1 and 10,000 parts per million to polymers therein, and the particle additive is capable of trapping at least one of hole charges or electron charges in the polymer dielectric.

Description

C18703_P18703-02002240.623016POLYMER DIELECTRICS WITH SOLID AND MOLECULAR PARTICLE INCLUSIONS FOR INCREASED ENERGY DENSITY IN CAPACITORSCROSS-REFERENCE

[0001] This application claims priority to U.S. Provisional Patent Application 63 / 770,164, filed March 11, 2025, the contents of which are incorporated herein in their entirety.GOVERNMENT LICENSE RIGHTS

[0002] This invention was made with government support under grant number N00014-23-1-2273 awarded by the Office of Naval Research. The government has certain rights in the invention.BACKGROUND1. Technical Field

[0003] The present disclosure relates to composite dielectrics for capacitors, and more specifically to composite dielectrics for capacitors and capacitors that have solid particle and molecular inclusions in the composite dielectrics.2. Introduction

[0004] Polymer-based dielectric capacitors are used in a variety of applications including energy storage systems, power electronics, and electronic devices due to their mechanical flexibility, processability, and charge-discharge characteristics. The performance of such capacitors depends in part on the dielectric properties of the polymer materials, including breakdown strength and energy storage density, which can be influenced by material composition and processing conditions. As demands for higher energy density and improved efficiency in capacitor technologies continue to evolve, there remains interest in approaches that may enhance the dielectric performance of polymer-based capacitor systems.SUMMARY

[0005] Additional features and advantages of the disclosure will be set forth in the description that follows, and in part will be understood from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out inC18703_P18703-02002240.623016 the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims, or can be learned by the practice of the principles set forth herein.

[0006] Disclosed are capacitors, composite dielectrics for capacitors, and methods of manufacture which provide a technical solution to the technical problem described. A composite dielectric for capacitors as disclosed herein can include: a polymer dielectric; and a particle additive distributed substantially uniformly in the polymer dielectric, wherein the particle additive is in a relative amount of between 1 and 10,000 parts per million to polymers therein; and wherein the particle additive is capable of trapping at least one of hole charges or electron charges in the polymer dielectric.

[0007] A capacitor configured as disclosed herein can include: a first electrode; a second electrode spaced apart from the first electrode; and a layer of a composite dielectric as described herein disposed between the first and second electrodes.

[0008] A method of manufacturing a capacitor, according to the steps disclosed herein, can include: providing a polymer solution comprising a polymer dielectric dissolved in an organic solvent; providing an additive dispersion comprising a particle additive selected from inorganic semiconductor particles or oxidizable or reducible organic molecular solids; combining the additive dispersion with the polymer solution to form a composite dielectric solution, wherein the particle additive is present in an amount between 1 and 10,000 parts per million by weight relative to polymer in the composite dielectric solution; agitating the composite dielectric solution to distribute the particle additive substantially uniformly within the polymer solution; depositing the composite dielectric solution onto a first electrode to form a dielectric layer; removing solvent from the dielectric layer to form a solid composite dielectric film; and forming a second electrode spaced apart from the first electrode with the solid composite dielectric film disposed therebetween.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 illustrates an example schematic diagram of breakdown field enhancement in polymer dielectric capacitors with nanoparticles;

[0010] FIG. 2 illustrates an example charge-discharge cycle of a capacitor ;C18703_P18703-02002240.623016

[0011] FIG. 3 illustrates example procedures for making thin-film capacitors and their device architecture;

[0012] FIG. 4 illustrates example graphs of capacitance and permittivity versus nanoparticle concentrations;

[0013] FIG. 5 illustrates example schematics of bi-layer capacitors;

[0014] FIG. 6 illustrates example comparisons of ft and i values between bi-layer and single-layer structures;

[0015] FIG. 7 illustrates an example schematic of a capacitor device in a dashed boxed;

[0016] FIG. 8 illustrates an example of chemical synthesis of PS-co-poly (4-vinylbenzylcyclobutene) (XLPS);

[0017] FIGS. 9 A, 9B, 9C, and 9D illustrate example graphs of capacitance and dissipation factor versus frequency; and

[0018] FIG. 10 illustrates an example method embodiment.DETAILED DESCRIPTION

[0019] Various embodiments of the disclosure are described in detail below. While specific implementations are described, this is done for illustration purposes only. Other components and configurations may be used without parting from the spirit and scope of the disclosure.

[0020]

[0021] An approach to improving performance of polymer dielectrics in capacitors is the incorporation of additives, including particles, but their utility has been limited. At excessive concentrations, the additives can agglomerate, leading to inhomogeneous properties and defects, increased dielectric loss, reduced breakdown strength, brittleness, and difficult scalability. At lower concentrations, permittivity improvements have been noted and heterostructured particles with advantageous trapping functionality have increased dielectric breakdown strength, but mechanisms to increase breakdown strength using dilute concentrations of homogeneous additives remain desirable but lacking. Therefore, there remains a need for improved composite dielectrics for capacitors and the capacitors that have solid particle inclusions in the composite dielectrics.

[0022] The phrase “particle additive distributed substantially uniformly” means sufficiently uniform to avoid agglomeration of particles.

[0023] Polymer-based dielectrics are desirable energy-storage media in capacitors. They offer scalable fabrication into thin and multilayered films, mechanical flexibility, low massC18703_P18703-02002240.623016 density, high resistivity, and mechanisms by which breakdown under high electric fields (“dielectric breakdown”) can be resisted. The energy density of a capacitor, the amount of electrical energy that can be stored per unit volume, is proportional to the square of the maximum electric field that can be applied to the capacitor without its breakdown (excessive conductance and / or loss of structural integrity), and to the relative permittivity of the dielectric. According to some configurations of the current invention, molecular additives and solid particles are introduced into polymer dielectrics to increase the breakdown field and / or the fractional energy recovered from discharging the capacitor (decreased energy loss). Some suitable additives are those with electronic energy levels that could intercept mobile charges that could be associated with dielectric breakdown. Additive mass fractions can be less than about 10,000 parts per million according to some configurations.

[0024] Accordingly, a configuration of the current invention includes the addition of additives, including small single-component particles at dilute mass fractions, for example, between 10 and 10,000 parts per million, to polymers used as capacitor dielectrics. In some configurations, the dielectric breakdown field is increased and / or the fractional energy loss is decreased. The small single-component particles can be compound inorganic semiconductors or oxidizable or reducible organic molecular solids. More specifically, in some configurations the inorganic semiconductors can include nickel oxide or zinc selenide. In addition, non-limiting examples of the organic particles can include dibenzotetrathiafulvalene (DBTTF) or tetrafluorotetracyanoquinodimethane (F4TCNQ). In some configurations, the particle additive material can be at least partly dispersed as a molecular solution. Note that there are other reasons why a dilute additive could be used with a polymer such as plasticization, chemical stabilization, cosmetic coloring, etc. Because the particle can be a molecule, this extends the additive class to all molecules as well as all particles. Other examples of the particles can include one or more blocks of a multiblock copolymer. The energy levels of the polymers can be such that they are capable of trapping charges that could be injected into the dielectric polymers during capacitor operation, thus inhibiting dielectric breakdown, increasing the maximum applicable electric field, and increasing the maximum possible energy density. In some configurations the polymers are hydrocarbon polymers or oxygenated polymers. For example, the hydrocarbon polymers can be polystyrenes, and / or the oxygenated polymers can be polycarbonates or polymethacrylates.C18703_P18703-02002240.623016 As an example, the polymers can be two or more dielectric polymer layers. Tn some configurations, particles are included in one or more of these layers.

[0025] For example, NiO:PS film capacitors with a mere 25 ppm per weight (ppmw) NiO loading level achieve a breakdown strength of 6.3 MV / cm. Similarly, ZnSe:PS film capacitors with as little as 5 ppmw ZnSe exhibit a breakdown strength of 6.4 MV / cm. Poly methyl methacrylate) with 1000 ppm of DBTTF showed breakdown strength of 6 MV / cm and energy density of 7 J / cm3. Polycarbonate with 10,000 ppm of DBTTF showed breakdown strength of 4.5 MV / cm, energy density of 3.7 J / cm3, and energy loss of 5%. Polycarbonate with 10,000 ppm of F4TCNQ showed breakdown strength of 4.5 MV / cm, energy density of 3.7 J / cm3, and energy loss of 6%. A polycarbonate-polystyrene bi-layer showed breakdown strength of 550 MV / cm and energy density of 11 J / cm3. A polystyrene diblock copolymer with one block having phthalimide side chains likely to be at least partially in a separate phase showed relative permittivity of 3.5 and essentially zero energy loss. The use of such a copolymer to template particle morphologies is contemplated. Use of crosslinked polystyrene instead of linear polystyrene increased capacitor reliability. A layer of crosslinked polystyrene in series with 25 ppmw ZnSe allowed increased breakdown strength accompanied by decreased energy loss that would occur via dissipation of polarization charge. The use of encapsulating materials to inhibit interparticle interactions is contemplated.

[0026]

[0027] Polymer-based dielectric capacitors represent a class of energy storage devices that store electrical energy through the polarization of a dielectric material disposed between two conductive electrodes. The energy storage density of such capacitors depends on both the relative permittivity of the dielectric material and the maximum electric field that can be applied before dielectric breakdown occurs. Because energy density scales with the square of the applied electric field, increasing the breakdown strength of the dielectric material provides a pathway to achieving higher energy storage capacity.

[0028] A technical challenge in polymer capacitor design involves balancing multiple performance parameters. Polymer dielectrics offer advantages including mechanical flexibility, low mass density, high resistivity, and compatibility with scalable thin-film fabrication processes. However, polymer dielectrics may exhibit lower breakdown strength compared to ceramic dielectrics, which limits the maximum achievable energy density. Additionally, energyC18703_P18703-02002240.623016 losses during charge-discharge cycles reduce the efficiency of energy recovery from the capacitor.

[0029] One approach to addressing these challenges involves modifying the dielectric material itself to suppress the electrical processes that lead to breakdown, rather than relying solely on increasing permittivity. When a strong electric field is applied across a polymer dielectric, mobile charge carriers may be injected from the electrodes or generated within the material. These carriers can accelerate under the applied field, accumulate at localized regions, and initiate conduction pathways that ultimately result in dielectric failure. By introducing carefully selected additives at extremely low concentrations into the polymer matrix, it is possible to create distributed electronic trap states that intercept these carriers before they contribute to avalanche conduction or localized field intensification. This strategy increases the maximum sustainable electric field while preserving the desirable mechanical and processing characteristics of the base polymer.

[0030] In one configuration, the dielectric layer comprises a polymer matrix containing ultra-dilute inorganic semiconductor particles dispersed substantially uniformly throughout the material. The semiconductor particles possess electronic structures that support localized trap states, including surface defects, vacancies, and non-stoichiometric sites capable of capturing electrons or holes. When incorporated at sufficiently low concentrations, these particles remain spatially isolated within the polymer matrix and do not form continuous conductive pathways. Under applied electric stress, injected carriers are captured at the particle surfaces, thereby reducing the effective mobile carrier concentration and limiting the formation of high-field conduction channels. As a result, the composite dielectric exhibits an increased breakdown strength relative to the unmodified polymer.

[0031] The concentration of such semiconductor particles is selected to remain below a level in which interparticle interactions become significant. At higher loadings, particles may approach one another closely enough to create localized field enhancement or percolation-like pathways that reduce dielectric reliability. In contrast, within the ultra-dilute regime, the average spacing between particles is sufficiently large that each particle acts as an independent trap center distributed throughout the film thickness. This configuration enables charge interception without compromising the insulating integrity of the polymer matrix. The dielectric permittivity of the composite remains substantially similar to that of the base polymer, indicating that theC18703_P18703-02002240.623016 primary performance improvement arises from enhanced breakdown strength rather than changes in polarization behavior.

[0032] The composite dielectric films can be fabricated using solution-based processing techniques that are compatible with conventional thin-film capacitor manufacturing. The polymer is dissolved in an appropriate solvent, and a dispersion of semiconductor particles is prepared separately. After combining and agitating the mixture to achieve uniform distribution, the composite solution can be deposited onto a conductive substrate to form a dielectric layer. Solvent removal yields a solid composite film, and a second electrode is formed to complete the capacitor structure. Filtration and controlled agitation may be employed to minimize agglomeration and ensure uniformity. The resulting films remain smooth and continuous, with minimal surface roughness, thereby avoiding the introduction of morphological defects that could otherwise initiate premature breakdown.

[0033] In another configuration, electroactive organic molecules are incorporated into the polymer dielectric at dilute concentrations. These molecules are selected based on their redox properties and electronic energy levels relative to those of the host polymer. Certain molecules function as electron donors and preferentially trap holes, while others function as electron acceptors and preferentially trap electrons. When dispersed molecularly within the polymer matrix, these additives introduce deep trap states that intercept carriers injected during capacitor operation. The trap states are sufficiently deep to immobilize carriers and suppress avalanche ionization, yet the concentration of molecules remains low enough that the bulk electronic structure and mechanical properties of the polymer are not substantially altered.

[0034] The incorporation of electroactive molecules can be achieved by blending solutions of the polymer and the selected additive, followed by deposition and solvent removal to form a thin dielectric film. At the dilute concentrations employed, the molecules remain dispersed without forming aggregates or crystalline domains observable by optical or electron microscopy, or by x-ray diffraction. Structural characterization indicates that the polymer matrix retains its amorphous nature, and surface analysis confirms that film morphology remains smooth and homogeneous. Electrical measurements demonstrate that the addition of these molecules increases the breakdown field in several polymer systems, thereby enabling higher recoverable energy density. In some cases, improvements in energy conversion efficiency are observed at moderate electric fields, reflecting reduced conduction losses due to effective charge trapping.C18703_P18703-02002240.623016

[0035] The effectiveness of a particular electroactive molecule depends in part on its compatibility with the host polymer. Differences in polymer backbone structure, polarity, and intrinsic conduction behavior influence how the introduced trap states interact with mobile carriers. In polymers with reduced intrinsic conduction pathways, the addition of deep traps can produce especially pronounced increases in breakdown strength. In other systems, improvements may be moderated by inherent loss mechanisms associated with the polymer itself. Nonetheless, the general principle of ultra-dilute trap engineering remains applicable across multiple classes of hydrocarbon and oxygenated polymer dielectrics.

[0036] Further improvements in reliability and cycling stability can be achieved through multilayer dielectric architectures. In one configuration, a crosslinked polymer dielectric layer is positioned adjacent to a composite dielectric layer containing either semiconductor particles or electroactive molecules. The crosslinked layer provides mechanical rigidity and resistance to crack propagation, while the composite layer provides distributed trap functionality. By distributing electric stress across multiple interfaces and reducing localized defect growth, the multilayer structure enhances durability under repeated charge-discharge cycling. Although the overall breakdown field of a multilayer structure may differ from that of an optimized singlelayer composite, improvements in uniformity and endurance are observed.

[0037] In both particulate and molecular implementations, the central principle is the creation of spatially distributed trap centers within the dielectric layer without introducing conductive networks or structural inhomogeneities. By maintaining additive concentrations within an ultra-dilute regime, the composite dielectric preserves low dielectric loss, stable permittivity, and smooth film morphology. The resulting capacitors exhibit increased breakdown strength and enhanced energy storage capability while retaining compatibility with scalable thin-film processing methods. This materials strategy provides a pathway toward high-performance polymer capacitors suitable for demanding energy storage and power electronics applications where both efficiency and reliability are critical.

[0038]

[0039] FIG. 1 illustrates diagrams of polymer capacitors showing charge injection leading to breakdown, charge interception by incorporated particles inhibiting breakdown, and plots of probabilities of breakdown for compositions with and without additives, represented by differentC18703_P18703-02002240.623016 shades, as a function of applied electric field. Higher breakdown fields are associated with additives.

[0040] With the global rise in energy demand and the pressing challenges of climate change driven by fossil fuel consumption, the development of advanced energy storage technologies has become indispensable for creating reliable energy supply systems and accelerating the transition to clean energy. Among various energy storage systems, capacitors, which store energy electrostatically, stand out for their high-power density and rapid charge-discharge rates, although they exhibit relatively low energy density compared to batteries and solid oxide fuel cells (SOFCs) that store energy electrochemically, and by contrast, possess high energy density but low power density. Owing to capacitors’ unique characteristics, dielectric capacitors have found widespread application across diverse fields, including renewable energy systems, smart power grids, medical devices, electric vehicles and electronic devices. One widely used class of dielectric materials for electrostatic capacitors is ceramics, because of their high relative permittivity (ranging from hundreds to tens of thousands), exceptional stiffness and excellent thermal stability. However, ceramics capacitors face limitations such as poor mechanical flexibility and low breakdown strength, which restrict their practical applications. In contrast, dielectric polymers offer compelling advantageous properties that make them excellent candidates for capacitor materials. These polymers typically exhibit high breakdown strength, rapid charge-discharge rates, low dielectric loss, and easy processing into thin fdms.Additionally, their intrinsic self-healing characteristics that effectively isolate the damaged sites after the dielectric breakdown, provide more reliable operation compared to ceramic counterparts.

[0041] A typical dielectric film capacitor comprises two conductive metal electrodes with an insulating polymer layer sandwiched in between. When an electric field is applied to the capacitor, the polymer is polarized in the direction of the field and charges accumulate at the surface of the conductive plates. Figure 2 illustrates the charge-discharge cycle of a capacitor. The recoverable energy density, density, Ureco, a key metric to evaluate the performance of capacitors, is represented by the grey dashed purple area, whereas the energy loss per cycle, Uioss, is represented by the enclosed green area within the hysteresis loop.C18703_P18703-02002240.623016

[0042] The recoverable energy density, Ureco, a key metric to evaluate the performance of capacitors, can be obtained by taking the integral of the area between the discharging curve and the horizontal projection of the maximum polarization and is expressed by the equation,UreCo = f E dD (1)where E is the electric field and D is the dielectric displacement. The dielectric displacement can be represented by,D = P + e0E = KC0E = eE (2)where P is the polarization, K is the relative permittivity, e is the dielectric permittivity and e0is the vacuum permittivity (e0= 8.854 x 10'12F / m). Hence, the energy density of linear dielectrics is derived to be,Ureco = ^oE2(3)e"

[0043] Normally, the dielectric loss tangent or dissipation factor, tan 8 = — , is used to describe the dielectric loss. For a pure dielectric capacitor, dielectric loss includes relaxation loss (also called polarization loss) and conduction loss. Relaxation loss may occur during the chargedischarge cycle where some unreleased energy is dissipated as heat under alternating electric field. Electrical conduction loss, caused by the current leakage, increases with increasing electric fields. More specifically, when the capacitor operates under high fields and high temperatures, the density and mobility of the charge carriers would increase, resulting in a large increase in the conduction current in the dielectrics; consequently, the current-voltage relation no longer adheres to Ohm’s law. Additionally, for a dielectric mixture, the interfacial polarization caused by the mismatch of the permittivity of the components in the mixture would lead to another type of dielectric loss. The energy loss refers to the area within the hysteresis loop (t / zoss). Thus, the charging-discharging efficiency, T , can be determined via this equation,P = yureUcor~ru° loss ■ (4)

[0044] To thoroughly assess the performance of the capacitor devices, Weibull probability analysis is generally adopted to provide a visual representation of the dielectric breakdown strength distribution and offer insights into the expected lifetime and failure characteristics of a batch of capacitors. The two-parameter Weibull distribution function, represented as a cumulative distribution function (CDF), is expressed as,C18703_P18703-02002240.623016where E is the measured breakdown field, / ) is the scale parameter, which represents the field strength at which 63% of devices are expected to fail and has the same unit as the breakdown field, and ft is the shape parameter (often termed “reliability” but really a measure of the narrowness of the distribution of x-axis values), which determines the shape of the CDFs and probability density functions (PDFs). A high i) value usually indicates a high overall breakdown strength for the capacitor population, which shows a robust dielectric material system. / ?, also known as the Weibull modulus, is the slope of the straight line on the Weibull probability plot and gives information about the consistency of the capacitor’s dielectric strength. If / ? < 1, the Weibull probability plot shows that failure rates decrease over increasing field (failure at initial turn-on). Conversely, / ? > 1 indicates that the failure rate increases with breakdown field strength (“wear-out failure”), which is generally considered more desirable because such failures are more predictable and manageable. Typically, a higher / ? suggests a tighter or narrower distribution of the dielectric breakdown strengths, meaning greater uniformity and predictability in the performance of a set of capacitor devices.

[0045] Commercial dielectric polymers include polystyrene (PS), polycarbonate (PC), polyethylene terephthalate (PET), and fluorinated ethylene propylene (FEP). Currently, the state-of-the-art polymer capacitor film is the biaxially oriented polypropylene (BOPP) film that is approximately 2.5 micron thick, with an outstanding breakdown strength (>700 V / wrn), low dielectric loss (< 0.02%), a relatively low yet temperature- and frequency- independent relative permittivity of 2.2, contributing to an overall energy density of ca. 3 J / cm3. It also has excellent mechanical flexibility and long lifetime (> 20,000 h) due to its self-repair property, which has been exploited in industrial capacitor fabrication. High volume loading (> 15 vol%) of nanofillers into the polymer matrix has been extensively studied to increase energydensity. However, the nanofillers can create localized electric fields at the polymer-filler interfaces, and when these localized fields exceed the external field, they significantly reduce the composite’s breakdown strength, thereby compromising dielectric reliability. To address this local field effect issue, one approach is making a multilayered structure, for example a threelayered BaTiOa nanocomposite capacitor with optimally tailored nanomorphology and composite structures in each layer. This design achieved a discharged energy density of 10 J / cm3C18703_P18703-02002240.623016 and a breakdown strength of 450 kV / mm, demonstrating a concurrent enhancement in dielectric strength and energy density. Another method involves modifying the surface structure of nanofillers to reduce local field, such as designing core-shell PS@ BaTiCh and PMMA@ BaTiCh composites and coating BaTiCh with pentafluorobenzylphosphonic acid (PFBPA). Other methods can also include the aggregation of particles leading to poor dispersibility, increased dielectric loss, reduced mechanical strength, and / or potentially higher cost leading to scalability issues.

[0046] Dilute nanofillers (< 0.5 vol%), including 1OW-K nanofillers such as SiO2 and MgO, lead to a large increase in the relative permittivity of linear dielectric polyetherimide (PEI) polymer, without compromising breakdown strength or thermal stability. In addition, a high-Tgdipolar polymer, poly(arylene ether urea) (PEEU) containing 0.2 vol% of alumina (AI2O3) nanofillers generated a high discharged energy density of ca. 5 J / cm3and high efficiency of 90% at 150°C. To explain such interesting phenomena of dilute nanoparticles, studies suggest that just a small amount of nanofillers can induce interfacial effect within the polymer by causing a dramatic increase in interfacial areas and boundaries and generating a large volume of interfacial polymer matrix. The interfacial region exhibits structure and properties that are vastly different from the bulk and more importantly, and seems to control the properties of the entire nanocomposite. Others have proposed that nanofillers create surface deep traps that capture charges, resulting in a significant decrease in the mobile carrier concentration and a reduced average free path for electron acceleration in polymers. This leads to a marked reduction in high-field conduction losses and thereby increases the breakdown fields. Overall, the low-filler design helps improve the interface compatibility between filler particles and polymer matrix, reduces the agglomeration of filler particles at high concentrations that create conduction pathways leading to breakdown, and saves raw materials.

[0047] As disclosed herein, the inventors investigated the effect of different nanoparticles on the dielectric properties of the composites. The investigation chose a common amorphous linear dielectric polymer, polystyrene (PS, Tg= 95 °C), as the host polymer. It is a nearly non-polar polymer that consists of long chains of styrene molecules with a dielectric permittivity of -2.55 and especially low loss tangent of 0.0002 in the glassy state. Two types of nanofillers, nickel oxide (NiO) and zinc selenide (ZnSe) nanoparticles, were incorporated at ultra-low concentrations into the PS matrix via solution casting. Both semiconducting fillers possessC18703_P18703-02002240.623016 accessible frontier energy levels capable of trapping injected charges. The resulting nanocomposite films exhibited enhanced breakdown strength, confirming that even dilute nanoparticle additions can significantly improve the dielectric properties of polymer nanocomposites. Other nanofillers, beyond NiO and ZnSe, are likewise within the scope of this disclosure.

[0048] Next, consider an exemplary process to create diluted NiO / ZnSe polystyrene nanocomposite dielectric capacitors. NiO nanoparticles are added to PS at concentrations of 5, 25, 62.5, 312 and 468 ppmw, while ZnSe nanoparticles were mixed with PS at 5, 25, 50, 250 and 750 ppmw. Note that these concentrations, while used for the investigation, are exemplary, and other concentrations are within the scope of this disclosure. Both NiO and ZnSe nanoparticles were visibly well-dispersed in organic solvents before being added to the PS solution. The capacitor film fabrication process is illustrated in Figure 3. More specifically, FIG. 3 illustrates procedures for making thin-film capacitors and their device architecture. In this example, PS solution 302 is dispensed onto the ITO / glass substrate and spin-coated 304 for a predetermined amount of time. The films were annealed 306 at (e.g., at 50 °C) for a subsequent predetermined amount of time (e.g., 1 hr), which slows the solvent evaporation and maximize smoothness and uniformity. The film fabrication process was conducted in the N2-filled glovebox. Gold electrodes 308 of three different sizes (0.005 cm2, 0.0254 cm2 and 0.21 cm2) (these are nonlimiting examples) were patterned onto the dry films through thermal evaporation under high vacuum, during which the residual solvent with high volatility would also have been removed. The nanocomposite dielectric capacitor consists of two conductive plates: one made of conductive ITO-layered borosilicate glass and the other of a 50-nm thick gold layer, with the nanofiller-PS thin film sandwiched in between. Nanocomposite prepared with capacitor areas of 0.21 cm2, 0.0254 cm2 and 0.005 cm2 (these are non-limiting examples) were investigated.

[0049] Film thicknesses were measured to be 2-3 microns, with exact values for all the samples summarized in Table SI, below. Polarization and breakdown strength of the thin film capacitors were characterized using a capacitor measurement system under bipolar and monopolar voltage sweeps at room temperature. Nanocomposites were prepared with capacitor areas of 0.005 cm2, 0.0254 cm2and 0.21 cm2.

[0050] The dielectric performance of dilute nanocomposite capacitors, fabricated with an electrode area of 0.0254 cm2was reviewed. Pristine polystyrene (PS) exhibited a polarization ofC18703_P18703-02002240.623016 0.54 / zC / cm2under both bipolar and monopolar charging at a breakdown field of 1.7 MV / cm. This behavior is consistent with the known characteristics of amorphous PS, which contains greater free volume and molecular disorder than crystalline or semicrystalline polymers. Such loose chain packing and structural irregularities contribute to its susceptibility to dielectric breakdown.Table 1. Tabulated data of two parameters, ft and rj extracted from the Weibull probability plots for capacitors with an area of 0.0254 cm2.

[0051] The breakdown fields of the nanocomposite PS samples were statistically analyzed using Weibull distributions. Shape ( / ?) and scale (fj) parameters summarized in Table 1.Incorporation of NiO nanoparticles at dilute concentrations significantly modulated dielectric breakdown performance. At 25 ppmw loading, the NiO: PS nanocomposite showed a 2.4-fold enhancement in breakdown strength (fj = 4.28 MV / cm). Increasing the filler content to 62.5 ppmw reduced fj slightly to 4.01 MV / cm, indicating a plateau in performance enhancement beyond this concentration. At 312 ppmw, the breakdown strength deteriorated substantially (fj = 1.38 MV / cm), suggesting filler overloading. The P-E loops of selected NiO: PS capacitors under bipolar and monopolar sweeps indicated dielectric losses, increased with the introduction of nanoparticles, but energy densities of the nanocomposites were improved due to the enhanced dielectric strength. Energy storage analysis revealed an energy density of 2.2 J / cm3at 25 ppmw NiO, significantly outperforming pristine PS (0.42 J / cm3). Higher filler concentrations decreased the energy densities to 0.97 J / cm3(62.5 ppmw) and 0.076 J / cm3(312 ppmw). Energy conversion efficiency also declined with filler addition beyond the lowest concentrations, dropping from 94% in pristine PS to 64%, 78% and 83% for 25 ppmw, 62.5ppmw and 312ppmw NiO loadings,C18703_P18703-02002240.623016 respectively. This trend correlated with the larger hysteresis loops observed in the NiO: PS samples.

[0052] ZnSe nanoparticles, with a larger average particle size (-200 nm, as determined by dynamic light scattering) and broader distribution than NiO (10-20 nm, per supplier data), induced more pronounced effects on dielectric behavior at low concentrations. A loading of 5 ppmw ZnSe significantly yielded a dielectric breakdown strength of J] = 3.90 MV / cm, with further enhancements at 25 ppmw and 50 ppmw (fj =5.85 and 5.52 MV / cm, respectively). These findings suggest that ZnSe nanoparticles enhanced dielectric strength more effectively than NiO at ultra-low filler concentrations. Analysis of P-E plots for ZnSe: PS capacitors indicated that energy densities reached 0.79 J / cm3, 2.18 J / cm3, 1.60 J / cm3, 0.67 J / cm3and 5.3 xIO’2J / cm3at 5 ppmw, 25 ppmw, 50 ppmw, 250 ppmw and 750 ppmw ZnSe loadings, respectively. Energy conversion efficiency varied across the samples, ranging from 47% to 98% depending on the filler concentration. Despite some reduction in efficiency at certain filler concentrations, the energy densities for ZnSe: PS samples with loadings between 5 and 250 ppmw remained superior to that of the pristine PS.

[0053] Both NiO and ZnSe nanocomposites followed a general trend where the breakdown strength improved at ultra-low filler loadings but degraded at higher concentrations. At ultra-low concentrations, the particles remained isolated. With increasing filler content, interparticle connectivity could have approached the percolation threshold. These percolation paths channeled electric fields through the fillers rather than the polymer matrix, leading to premature breakdown.34

[0054] As described above, breakdown strength enhancement was attributed to the nanoparticles’ effective surface trapping mechanism. One interpretation of how surface trapping works for the two nanoparticles, / -type NiO (wide indirect bandgap =3.5 eV) and w-type ZnSe (direct bandgap = 2.7 eV), is as follows. The high surface-to-volume ratio of nanoparticles led to an abundance of surface atoms with unsaturated bonds or defects, generating localized energy states within the bandgap that trapped charge carriers. Additional trap states arose from vacancies (Zn, Se, Ni, O) and interstitial defects (e.g., Zn substituting for Se, Ni substituting for O, and vice versa). Zn vacancies acted as hole traps due to their acceptor-like behavior whereas Se vacancies were more prone to trap electrons owing to their donor-like characteristics. For NiO, their non-stoichiometric surfaces contained predominant Ni3+sites. When holes wereC18703_P18703-02002240.623016 trapped, Ni3+were oxidized to Ni4+state, which is close to the valence band edge, whereas when electrons were trapped, Ni3+was reduced to Ni2+state.35

[0055] Pristine PS exhibited a ft value of 3.70, while nanocomposites generally exceeded p =4.0. The 5 ppmw ZnSe: PS composite achieved P = 11.53, indicating significant enhancement in device reliability and breakdown consistency. Higher ft values observed in the nanofiller-integrated capacitors suggest greater uniformity and improved homogeneity in the dielectric breakdown distribution.

[0056] To exclude the possibility that the particles form conductive pathways on the top surface, which could potentially increase the effective electrode area or capacitor area, an approximate calculation was performed to estimate the distances between nanoparticles. Detailed calculations and explanations are provided Table S2 below. For instance, the average interparticle spacing of NiO in the 25 ppmw NiO:PS composite is estimated to be 1.02 x 10’4cm, approximately half of the film thickness. In contrast, the interparticle spacing in the 5 ppmw ZnSe:PS composite is 1.61 xlO'3cm, which is larger than the film thickness. These calculations suggest that the particles were spaced far apart within the PS matrix at low loading, with minimal likelihood of forming conductive channels that could increase the effective capacitor area and thus be the origin of observed relative permittivity increases.

[0057] In summary, for capacitors with a device area of 0.0254 cm2, ultra-dilute loadings of both NiO and ZnSe significantly enhanced dielectric breakdown strength, increasing accessible fields and polarization values. The energy storage density is correspondingly increased, even after accounting for the increased loss and charge trapping observed from the addition of the nanoparticles.

[0058] To evaluate performance at reduced device dimensions, where there was lower probability of including the largest particles that could locally short-circuit the dielectrics, dielectric properties of nanocomposite capacitors with 0.005 cm2electrode areas were measured. The characteristic breakdown strength (p) extrapolated from Weibull failure analysis (see Table 2), followed the same trend that was observed for the 0.0254 cm2devices. For the NiO:PS samples, a substantial improvement over the pristine PS baseline (fj = 2.78 MV / cm) was achievedC18703_P18703-02002240.623016Table 2. Tabulated data of two parameters, p and 77 extracted from the Weibull probability plots.at ultra-low filler concentrations. At concentrations of 25 ppmw, 62.5 ppmw and 312 ppmw, 77 values of 6.11 MV / cm, 6.40 MV / cm and 5.59 MV / cm were obtained, representing a 2.2- to 2.5-fold enhancement. However, increasing the NiO filler concentration beyond this optimal range led to a decline in performance. At the highest loading (468 ppmw), the nanocomposite’s dielectric integrity was severely compromised. This performance trend was reflected in the representative P-E loops. For the ZnSe: PS samples, the introduction of 5 ppmw ZnSe increased 77 to 6.07 MV / cm. fj values then stabilized between 5.88 MV / cm and 5.40 MV / cm across a broader concentration range of 25-250 ppmw. Further increasing the loading to 750 ppmw reduced fj to 3.51 MV / cm, though still above that of pristine PS.. Pristine PS consistently exhibited higher Weibull modulus ( / ? = 13.53) than the nanocomposite capacitors, likely due to the non-uniform distribution of the nanoparticles within the PS matrix, which compromised the homogeneity of device performance.

[0059] Note that the high polarization values observed in these 0.005 cm2devices were an artifact of the fringing fields rather than an intrinsic material enhancement from the nanoparticles. Therefore, the primary benefit of nanofiller addition at these dimensions is the confirmation of the increased breakdown strength. While the breakdown enhancements mirrored those of the 0.0254 cm2devices, energy density values could not be meaningfully evaluated due to fringing effects.

[0060] Larger-area capacitors (0.21 cm2) were compared to smaller-area devices (0.0254 cm2and 0.005 cm2) in terms of breakdown strength and device reliability. The dielectric breakdown trend of the large-area nanocomposite capacitors resembled that of the smaller-areaC18703_P18703-02002240.623016 devices. However, the Weibull probability plots (with data in Table 3) revealed that most ft values of the large-area capacitors fell between 2.5 and 6.0, overall lower than those of the smallarea capacitors. These Weibull results suggested that the large-area capacitors contained more defects, leading to a reduced average breakdown field strength in each nanocomposite.Table 3. Tabulated data of two parameters, ft and fj extracted from Weibull probability plots.

[0061] Furthermore, the observed polarization values of the large-area NiO:PS and ZnSe:PS capacitors were significantly lower than those of the small-area PS capacitors, presumably due to the short-circuiting within the film devices; therefore, energy density calculations from the P-E loops were not meaningful.

[0062] Capacitances and loss tangents of the large-area (0.21cm2) nanocomposite capacitors were measured using an LCR meter. As shown in Figure 4, capacitances measured at 1 kHz and IV at room temperature fell within reasonable values and exhibited very low loss tangents (0.0001-0.0008). The calculated relative permittivity (K) values are also presented in the figure. Capacitance measurements 402, 406 using the LCR meter at 1 kHz and IV and the calculated relative permittivity for (a) NiO:PS samples and (b) ZnSe:PS samples with an electrode area of 0.21 cm2. FIG. 4 also illustrates the relative permittivity, k, 404, 408 for the (a) NiO:PS samples and (b) ZnSe:PS samples, respectively. The loss tangents measured for all the samples are between 0.0001 and 0.0008. Numerical data, including uncertainties, are also tabulated in Tables S3 and S4. The K values of the large-area (0.21 cm2) pure PS film capacitors (2.48 - 2.50), obtained from monopolar and bipolar P-E loop, were close to the bulk PS value (K = 2.55).Based on the LCR meter’s results, nanocomposites with ultra-low nanofiller loadings showed slightly higher K values than pristine PS (K = 2.49). Specifically, the 25 ppmw and 62.5 ppmw NiO:PS samples showed K values of 2.53 and 2.54, while the 5 ppmw and 25 ppmw ZnSe:PSC18703_P18703-02002240.623016 capacitors exhibited K values of 2.74 and 2.52, respectively. At higher fdler loadings, K values declined slightly. Overall, the LCR measurements are logical and reliable. Thus, although large-area capacitors show apparent increases in breakdown field, the higher likelihood of defect-induced current leakage and reduced polarization limited observable energy storage in this geometry.

[0063] In single-layer dielectrics, defects or inhomogeneities appeared to limit the practicality of our nanocomposites when used in capacitors with macroscopic areas. To investigate whether bilayer nanocomposites could produce better dielectric performance than that of single-layer structures, the investigation fabricated capacitors with a cross-linked PS (XLPS) base layer and a top layer composed of either pristine PS as a reference or nanocomposite dielectric, as illustrated in Figure 5. FIG. 5 illustrates example schematics of bilayer capacitors, in which the dielectric stack consisted of a cross-link polystyrene (XLPS) base layer and a nanocomposite top layer. In (a), gold 502 and an ITO / borosilicate substrate 508 have a bilayer dielectric with PS 504 and XLPS 506. In (b), the bilayer dielectric is NiO-PS 510 and XLPS 506. In (c), the bilayer dielectric is ZnSe-PS 512 and XLPS 506. The use of XLPS 506 was motivated by its chemical compatibility with regular PS, since both share styrene repeat units and similar surface chemistry.

[0064] Weibull probability analysis (see Table 4) revealed that baseline XLPS / PS devices exhibited fj values of 1.40 MV / cm, 1.93 MV / cm and 1.99 MV / cm for electrode areas of 0.21 cm2, 0.0254 cm2and 0.005 cm2, respectively. A notable difference was observed in the Weibull modulus: the 0.005 cm2devices achieved / ? = 31.28, compared to 7.54 and 4.86 forC18703_P18703-02002240.623016 Table 4. Tabulated data of and fj values derived from the Weibull probability plots. The bilayer capacitor samples exhibit higher ft values, suggesting reduced variability in dielectric breakdown strength compared to their single-layer counterparts.the 0.0254 cm2and 0.21 cm2devices, suggesting superior performance uniformity at smaller dimensions for XLPS / PS. Incorporating NiO nanoparticles resulted in a significant enhancement of breakdown strength. For XLPS / 25 ppmw NiO:PS bilayer, fj values increased to 2.46 MV / cm 3.24 MV / cm and 6.20 MV / cm for 0.21, 0.0254, and 0.005 cm2devices, respectively. The NiO:PS bilayer devices showed improved (15.92) at 0.21 cm2but reduced (10.43) at 0.005 cm2compared to the baseline XLPS / PS. Similarly, the inclusion of ZnSe nanofillers enhanced breakdown strength relative to the baseline, yielding fj values of 2.43 MV / cm, 3.59 MV / cm and 4.74 MV / cm for 0.21 cm2, 0.0254 cm2and 0.005 cm2areas, respectively. The ZnSe bilayers exhibited ft values of 5.82, 14.34 and 6.40 for the same areas, which are higher than the baseline at 0.21 cm2and 0.0254 cm2but lower at 0.005 cm2.

[0066] When comparing the dielectric performance of single-layer and bilayer capacitors (as illustrated in FIG. 6), the bilayer architecture exhibited higher Weibull modulus but lower dielectric breakdown strength. For example, FIG. 6 illustrates a comparison of ft and rj values between bilayer and single-layer structures - pristine PS vs. XLPS / PS, 25 ppmw NiO: PS vs. XLPS / 25 ppmw NiO: PS, 25 ppmw ZnSe: PS vs. XLPS / 25 ppmw ZnSe: PS - was conducted for three electrode areas: (a) 0.21 cm2(b) 0.0254 cm2and (c) 0.005 cm2. As noted above, these areas are non-limiting examples. The dielectric breakdown strength (r) of the bilayer structures was lower than that of the corresponding single-layer devices, whereas the bilayer structures exhibit higher ft values.

[0067] Such observation can be explained by material and structural factors. Cross-linked PS is mechanically more rigid and chemically more resistant to local defect growth than linear PS. When used as the base layer, it may suppress microcrack propagation and charge migration, improving the reliability of the device performance. However, cross-linked PS is inherently porous, introducing network defects and free volume, reducing breakdown strength relative to neat PS nanocomposites. Interfacial mismatch between the two layers may also lower breakdown strength. Thickness also plays a dual role: breakdown strength typically decreases with increasing film thickness, and bilayer capacitors are thicker than the single-layer devices, whichC18703_P18703-02002240.623016 can partly explain the lower breakdown strength. Yet, greater thickness can enhance reliability by distributing the electric field over a larger volume, so that the localized defects would have less chance to short the whole capacitor device.

[0068] Compared to single-layer devices, bilayer structures displayed slimmer hysteresis loops, indicating little dielectric loss and mitigating anomalies observed with single layers.Incorporation of nanofillers into bilayer capacitors resulted in a significant improvement in energy storage capabilities. For 0.21 cm2devices, the bilayer structures exhibited reasonable polarization values, as opposed to the anomalously low polarization obtained in the single-layer structures due to short-circuiting. The energy densities of 0.21 cm2bilayer devices increased from 0.27 J / cm3for XLPS / PS to 0.54 J / cm3and 0.86 J / cm3for XLPS / 25 ppmw NiO: PS and XLPS / 25 ppmwZnSe: PS, respectively. Notably, XLPS / PS, XLPS / 25 ppmw NiO: PS and XLPS / 25 ppmw ZnSe: PS demonstrated remarkable efficiencies of 97.9%, 95.1% and 97.3%, suggesting that there is a substantial reduction in energy loss compared to their single-layer counterparts. For 0.0254 cm2bilayers, nanocomposite devices achieved threefold higher energy densities (1.58 J / cm3for XLPS / 25 ppmw NiO: PS and 1.74 J / cm3for XLPS / 25 ppmw ZnSe: PS), compared with pristine PS bilayer (0.543 J / cm3), with corresponding efficiencies of 96.0%, 88.5% and 93.4%. The bilayer architecture thus reduced hysteresis loss and enabled high conversion efficiency, underscoring its potential for efficient energy storage. For 0.005 cm2bilayers, as mentioned earlier, pronounced fringing fields led to inflated polarization values and overestimated energy densities, and therefore, it is not meaningful to report or compare their energy densities here.

[0069] Cycling stability was further evaluated for single-layer 25 ppmw NiO: PS and 25ppmw ZnSe: PS, along with their bilayer counterparts, XLPS / 25ppmw NiO: PS and XLPS / ZnSe: PS. Under repeated electrical stress below breakdown or failure point, the singlelayer 25 ppmw ZnSe:PS exhibited clear dielectric degradation after the first high-field cycle, and subsequent cycles had to be performed at a significantly reduced electric field; the enlarged P-E loops indicated hysteresis loss during the charge-discharge process. The single-layer 25 ppmw NiO:PS failed after only five high-field cycles. Such degradation in single-layer capacitors is attributed to high electrical stress, which promotes the growth of microscopic defects and facilitates charge injection pathways. By contrast, the bilayer capacitors demonstrated markedly enhanced cycling stability. Both XLPS / 25 ppmw ZnSe:PS and XLPS / 25 ppmwNiO:PSC18703_P18703-02002240.623016 sustaining 15 charge-discharge cycles without evident degradation, as confirmed by their slim hysteresis loops.

[0070] The shapes and sizes of the nanoparticles were determined by scanning electron microscopy (SEM) on dispersions of particles cast from chlorobenzene (NiO) and chloroform (ZnSe). Both images reveal particles larger than the nominal 100 nm. The surface morphology of ZnSe: PS and NiO: PS films was further characterized by atomic force microscopy (AFM). The root-mean-square (RMS) surface roughness of ZnSe: PS and NiO: PS films is comparable to that of neat of PS films, indicating that dilute nanoparticle loading does not significantly alter film morphology. Film quality is crucial, as imperfection inside the polymer composites can arise from fabrication limitations and surface exposures. Such defects often reduce the experimental breakdown strength relative to the intrinsic value of the polymer composites. In our study, the extremely small surface roughness values confirm that the films are mostly smooth and continuous, which is highly desired for making high-performance capacitor devices.

[0071] In summary, the investigation validated that the principles and methods disclosed herein for enhancing the dielectric breakdown strength of polystyrene nanocomposites through the incorporation of ultra-low concentrations of NiO and ZnSe spherical nanofillers. The biphasic dependence of dielectric properties on filler loading is observed: the best-performing samples were identified at minute content loading, while higher concentrations led to a degradation in both the relative permittivity and breakdown strength of the nanocomposites. The decline was attributed to the onset of percolation pathways, which compromised the material’s near insulating integrity. Furthermore, the bilayer capacitors employing these ultra-low nanofillers also demonstrated enhanced dielectric breakdown strength and lower losses compared to pristine PS bilayer capacitors.

[0072] These findings unlocked new avenues for the rational design of high-performance dielectrics. The principles involving the interfacial phenomena between the polymer and nanofiller at ultra-low loading can be extended to a broader class of polymers with varying crystallinities and polaritiesC18703_P18703-02002240.623016Table SI. Thicknesses measured using profilometer for the single-layer NiO:PS and ZnSe:PS capacitor thin films.

[0073] To demonstrate that the nanoparticles do not form conductive pathways on the top surface that could increase the effective electrode / capacitor areas, we performed a crude calculation to estimate the distribution of distances (d 706, as shown in Figure 7, which shows a schematic illustration of one capacitor device circled in the dashed box 708) between nanoparticles. As in previous examples, the dielectric is formed between gold 502 and ITO / Borosilicate 508. In the illustrated example, the nanoparticles 704 are evenly distributed (i.e., in an ideal case). The calculation process is as follows: First calculate the volume ratios of NiO: PS and ZnSe: PS from their weight ratios knowing the densities of PS nanoparticles 702, NiO and ZnSe. From each calculated volume ratio and the known capacitor device volume, next determine the total volume of the nanoparticles 704. Assuming the nanoparticles are spherical, and their sizes are known (10-20 nm for NiO and 200 nm for ZnSe), estimate the number of nanoparticles within a single capacitor device. Assume that the particles are evenly distributed in a cubic lattice, and based on this assumption, the interparticle spacing (d), defined as the center-to-center distance between particles, is calculated as the cube root of the effective lattice volume. The following table presents calculations for two cases: 25 ppmw NiO: PS and 5 ppmw ZnSe: PS. The investigation selected a thickness of 2.5 pm and a surface area to be 0.0254 cm2for our calculations.Examples of calculationsC18703_P18703-02002240.623016Table S2. Detailed calculations of the interparticle spacing of NiO in 25 ppmw NiO: PS composite and ZnSe in 5 ppmw ZnSe: PS composite.

[0074] Based on our calculations, the interparticle spacing of NiO in the 25 ppmw NiO: PS composite is estimated to be 1.02 xIO'4cm, approximately half of the film thickness. In contrast, the interparticle spacing in the 5 ppmw ZnSe: PS composite is 1.61 * 10’3cm, which is larger than the film thickness. These calculations suggest that the particles are spaced far apart within the PS matrix at low loading levels, with minimal likelihood of forming conductive channels that could increase the effective capacitor area.C18703_P18703-02002240.623016 Table S3. Tabulated capacitance measurements and calculated dielectric constants for singlelayer NiO: PS samples at different nanoparticle concentrations, based on Figure 6 from the main text. For each nanocomposite sample, 12-14 capacitance measurements were collected and averaged.Table S4. Tabulated capacitance measurements and calculated dielectric constants for singlelayer ZnSe: PS samples at different nanoparticle concentrations, based on Figure 6 from the main text. For each nanocomposite sample, 12-14 capacitance measurements were collected and averaged.

[0075] FIG. 8 illustrates an example of synthesis of PS-co-poly (4-vinylbenzylcyclobutene) (XLPS). Here, a solution containing styrene, 4-vinylbenzylcyclobutene 802 (10 wt% relative to styrene, serving as a cross-linking agent) and 2,2'-azobis(2-methylpropionitrile) 804 (AIBN, 1% mol% relative to the total monomers) was prepared in chlorobenzene (2 mb per 2 g of monomers) in a Schlenk flask. The flask was evacuated and purged with nitrogen gas three times to establish an inert atmosphere. The reaction mixture was then stirred vigorously and heated at 63 °C in an oil bath 806 for 48 h. Upon completion, the solution was then cooled to room temperature and precipitated into 150 mL of methanol. The resulting polymer was collected, dissolved in tetrahydrofuran (THF), reprecipitated twice, and subsequently dried under vacuum at 60 °C, affording cross-linked polystyrene (XL-PS) in 90% yield 808. *HNMR (400 MHz, CDCh): o = 7.07, 6.59, 3.08, 1.85, 1.43; Mn: 24600; polydispersity index (PDI): 2.13. Detailed information regarding synthesis and polymer characterizations can be found in the previous publication.C18703_P18703-02002240.623016

[0076] Tn testing the principles described herein, the following materials and preparations were used / taken:

[0077] Materials

[0078] Polystyrene (PS, average Mw~ 50,000), zinc selenide (ZnSe, powder, 10 / zm, 99.99% trace metal basis), anhydrous chloroform (>99%) and anhydrous chlorobenzene (>99%) were purchased from Sigma Aldrich. Nikel oxide (NiO, nanopowder, 10-20 nm, 99% purity) was purchased from US Research Nanomaterials, Inc.

[0079] Solution preparation

[0080] Polystyrene (PS) solution was prepared by dissolving PS pellets in anhydrous chlorobenzene (200 mg / mL) at 45 °C overnight until the solution became homogeneous and transparent. To prepare the ZnSe nanoparticle solution, we followed a recipe described by Benmehdi et al. 10 mb of chloroform was added to 100 mg ZnSe powder (Sigma Aldrich) in a 20 mL glass vial and the yellow mixture was stirred for 3 hrs at 40 °C. Afterwards, the yellow mixture was allowed to sit for about 15 minutes, enabling the heavy ZnSe grains settle to the bottom of the vial, leaving the colloidal nanoparticles suspended on the top of the solution. The top portion of the solution was carefully pipetted out and transferred to an 8 mL vial for use. The NiO nanoparticle solution was prepared by sonicating the NiO powder in chlorobenzene (0.5 mg / mL) in an ultrasonic bath (BRANSON 1510, 40 kHz transducer) for 3 hrs to obtain a homogeneous solution. The ZnSe:PS solutions were prepared by mixing the PS solution with the ZnSe nanoparticle solution at 5 ppmw, 25 ppmw, 50 ppmw, 250 ppmw and 750 ppmw weight ratios. Similarly, the NiO:PS solutions were prepared by mixing the PS solution with the NiO nanoparticle solution at 25 ppmw, 62.5 ppmw, 312 ppmw and 468 ppmw weight ratios. All the mixture solutions were sonicated for 4-5 hrs to ensure the nanoparticles were well-dispersed in the PS matrix.

[0081] Capacitor film fabrication

[0082] The l-inch*l-inch indium tin oxide (ITO)-deposited borosilicate glass substrates were successively cleaned in an ultrasonicated bath with water, acetone and isopropyl alcohol to remove majority of impurities, followed by ultraviolet-ozone exposure to remove organic impurities and create an ionic layer on the glass surfaces. For each fdm, 500 z L of the NPs: PS solution was dispensed onto the ITO / glass substrate and spin-coated at 1000 rpm for 30 seconds. The films were annealed at 50 °C for 1 hr, which was to slow the solvent evaporation andC18703_P18703-02002240.623016 maximize smoothness and uniformity. The film fabrication process was conducted in the N2-filled glovebox. Gold electrodes of three different sizes (0.005 cm2, 0.0254 cm2and 0.21 cm2) were patterned onto the dry films through thermal evaporation under high vacuum, during which the residual solvent with high volatility would also have been removed. The ZnSe:PS and NiO:PS capacitor films were ready for capacitance characterizations. For the fabrication of bilayer capacitor devices, a layer of cross-linked polystyrene (150 mg / mL in chlorobenzene) was deposited onto the ITO / glass substrate and annealed at 200 °C for 2 hrs to ensure complete crosslinking. The annealing temperature was ramped up slowly from 50°C at a rate of 20 °C every 2 minutes. Subsequently, the NiO: PS or the ZnSe: PS solution was deposited on the XLPS base layer and annealed at 50 °C for 1 hr. Detailed information regarding XLPS synthesis can be found below. 8-12 devices were made for each nanocomposite condition.

[0083] Polarization and Breakdown Field Strength Measurement

[0084] The polarization and breakdown field measurements were conducted using a RADIANT TECHNOLOGIES instrument at 100Hz to produce P-E hysteresis loops.Capacitances are calculated from the P-E loops with known thickness and surface areas of the parallel plates. The relative permittivity and energy densities (including energy loss and energy recovered areas) are also calculated. An language-based package, developed fully in-house, is used to process all the raw data obtained from the instrument and to perform all the mathematical calculations / integrations including the energy densities and efficiencies as well as data visualizations.

[0085] Weibull Analysis

[0086] The two-parameter Weibull function was employed to describe the distribution of the breakdown fields (or breakdown voltages). A modified python language - based package was used to process the breakdown field data for all the samples and to calculate the probability distribution function.

[0087]

[0088] Next, we consider details for the solution blending of these four small molecules with the three dielectric polymers, where the small molecules are blended at concentrations varying from 0.01-1 wt.% with respect to the concentration of polymer in solution. Despite the very different orbital energies of the small molecules compared to those of the polymers, they are used in such dilute concentrations that the molecules should not affect the preponderant energyC18703_P18703-02002240.623016 levels of the polymers. The mechanical properties of the polymers should also not be significantly affected by the small molecules. The blends are filtered and spin coated on indium tin oxide (ITO)-coated borosilicate glass substrates, after which gold top-contact electrodes are thermally deposited to produce a variety of polymer capacitors. Polarization-field loops are acquired and subsequently analyzed to determine capacitor energy density and efficiency. It is found that blending as little as 0.01 wt.% of the electroactive small molecules into each of the three polymer dielectrics results in enhanced breakdown strength and consequently larger energy density to be observed in the polymer capacitors, with additional improved efficiency observed in additive containing capacitors at submaximal electric fields. The results demonstrate the application to energy management of new compositions of organic polymer electronic materials, with interfacial effects on performance as well.

[0089] The following experiments were conducted to prove these principles.

[0090] Substrate and Spinning Solution Preparation. Indium tin oxide (ITO)-coated borosilicate glass substrates were cut into 24 mm squares before being submerged and sonicated in solutions of deionized water, acetone, and isopropyl alcohol for 15 minutes each. Several solutions each of 25 wt.% of PS in chloroform, 12.5 wt.% of PC in chloroform, and 25 wt.% of PMMA in chlorobenzene were prepared in small glass vials and sonicated for at least 3 hours in a 50°C water bath. Additional solutions of 2.5 wt.% of 2,3,5, 6-tetrafluoro-7, 7,8,8-tetracyanoquinodimethane (F4TCNQ) in chloroform, 2.5 wt.% of Dibenzotetrathiafulvalene (DBTTF) in chloroform, 2.5 wt.% of 2,2'-(perfluoronaphthalene-2,6-diylidene)dimalononitrile or 1,3,4,5,7,8-hexafluorotetracyanonaphthoquinodimethane (F6TCNNQ) in chloroform, and 2.5 wt.% of Tetrakis(methylthio)tetrathiafulvalene (TMT-TTF) in chloroform were prepared in separate small glass vials and sonicated with the same conditions as the polymer solutions. All polymers, small molecules, and solvents were used as purchased without further purification.

[0091] Deposition of Dielectric Layer. After the polymers were fully dissolved, either 0.01, 0.10, or 1.00 wt.% of F4TCNQ, DBTTF, F6TCNNQ, or TMT-TTF was added to each polymer solution by using a 100 pL pipette. After the addition of the small molecules to the polymer solutions, all solutions were sonicated for an additional 30 minutes in a 50°C water bath. All polymer solutions were then filtered into a new, small glass vial using a 0.45 pm hydrophobic PTFE syringe filter. After filtering the solutions, ITO-coated substrates were dried under nitrogen gas flow and enough of each solution was deposited on the surface to cover theC18703_P18703-02002240.623016 substrate. Substrates were then spun at 2000 rpm with a spin acceleration of 1000 rpm / s for 60 seconds and immediately dried in a vacuum oven set to 100°C and a pressure of approximately 50 cmHg for 1 hour.

[0092] Deposition of Gold Electrodes. Once removed from the vacuum oven, 50 nm of gold was thermally evaporated at a rate of 0.4 A / s through shadow masks to produce eight rectangular electrodes per sample, with each electrode possessing an area of 0.21 cm2.

[0093] Electrical Measurements of Devices. The polarization-field curves of each sample were then obtained at 10 Hz using a RADIANT TECHNOLOGIES Precision RT66C Ferroelectric Tester by applying voltage to the bottom ITO surface of the sample and measuring the polarization of each independently responding device, typically at least four per composition. Leakage current measurements of each device were conducted in the same manner in an electrical probe station, with leakage current measured as a function of applied voltage from -100 V to +100 V with a step size of 1 V. Lastly, the frequency -dependent capacitance and corresponding dissipation factor of each sample were measured in the range of 100 Hz to 100 kHz using an AGILENT 4284A LCR Meter.

[0094] X-ray Diffraction and Surface Analysis. X-ray diffraction (XRD) patterns were obtained of polymer films deposited on clean silicon wafers by operating a BRUKER D8 Advance diffractometer using Cu Ka radiation. Scans were measured from 5 to 40° 20 at a 0.01° increment and a rate of 0.5° per minute with the detector in 0D mode. The thickness of each capacitor dielectric layer was measured in at least five unique locations using a FILMETRICS F20 Thin-Film Analyzer to determine the electric field applied to each device. Three-dimensional images of the top surface of the dielectric layer of each device were obtained using a KEYENCE VK-X 100 optical laser microscope.

[0095] Results

[0096] The polarization-field (P-E) loops of PS, PC, and PMMA single layer capacitors were acquired and analyzed to determine the energy density and efficiency of each capacitor. The energy density of each capacitor is calculated using the following equation

[0097] In Equation 6, Ueis the energy density of the capacitor, sris the relative dielectric constant of the capacitor dielectric, so is the vacuum permittivity, Eb is the breakdown strength of the capacitor (taken as the largest electric field applied to the capacitor before failure isC18703_P18703-02002240.623016 observed), and Ph is the maximum polarization of the capacitor at Eb. In addition to calculating the energy density, the efficiency ( |) of each capacitor is calculated using the following equation.

[0098] In Equation 7, Udischarged is the area bound by the upper curve of the P-E loop and the horizontal line that intersects the maximum polarization, while Uioss is the area bound between the lower curve and upper curve of the P-E loop. The highest obtained energy densities are reported in the main text below, with means and standard deviations provided in Tables SI -S3.

[0099] Significant increases in maximum polarization and breakdown strength are observed when either DBTTF, F4TCNQ, or TMT-TTF are blended with PS. The breakdown strength of a single layer PS capacitor with no additives is found to be 340 MV / m, while blending just 0.1 wt.% of F4TCNQ increases the breakdown strength 26% to 430 MV / m and blending 1 wt.% of TMT-TTF realizes a 56% increase in breakdown strength to 530 MV / m. This results in an energy density of 4.77 J / cm3observed in the PS with 1 wt.% TMT-TTF capacitor, a 192% increase relative to the PS control capacitor. Increases in energy density of PS capacitors are also accompanied by increases in loss. Losses as great as 32% are observed in the PS with 0.1 wt.% F4TCNQ capacitor, while the best performing PS with 1 wt.% TMT-TTF capacitor exhibits a loss of 27%, both significantly larger than the 14% loss exhibited by the PS control capacitor.

[0100] Replacing PS with PC results in significantly improved device performance. Similar to PS, the blended electroactive small molecules serve to increase breakdown field strength and consequently the maximum energy density of PC capacitors. The PC control capacitor exhibits a maximum energy density of 4.79 J / cm3at an electric field of 490 MV / m, comparable to the best performing PS capacitors. The addition of just 0.01 wt.% F4TCNQ to PC increases the maximum energy density by 56% to 7.27 J / cm3at an electric field of 630 MV / m, while the addition of 1 wt.% TMT-TTF profoundly increases the maximum energy density by 80% to 8.39 J / cm3at an electric field of 740 MV / m. Small decreases in loss can be observed in additive containing capacitors relative to the PC control capacitor up to the breakdown strength of the control capacitor at 490 MV / m, with significant decreases in loss being apparent in the PC with 1 wt.% TMT-TTF capacitor. The addition of 1 wt.% DBTTF to PC does not have the same effect as the addition of 0.01 wt.% DBTTF to PC, as losses at equivalent electric fields are comparable between the PC control capacitor and the PC with 1 wt.% DBTTF capacitor. Maximum losses ofC18703_P18703-02002240.623016 19% are observed in PC capacitors with 1 wt.% DBTTF and 0.01 wt.% F4TCNQ at breakdown fields of 560 MV / m and 630 MV / m, respectively, yet below 500 MV / m the losses of the best performing PC capacitors are typically in the range of 1% to 14%, consistent with the best performing polymer film capacitors in the literature.

[0101] Further increases in capacitor performance relative to PS and PC capacitors are realized through the utilization of PMMA, though the effects of the additives on breakdown field itself were less pronounced. A highest maximum energy density of 12.50 J / cm3was observed at an electric field of 770 MV / m for the PMMA control capacitor, further increased by 30% upon addition of 0.1 wt.% F4TCNQ to 16.20 J / cm3(mean value 14.1±3.0 J / cm3) at an electric field of 850 MV / m. However, unlike PS and PC, DBTTF did not serve to improve the energy density or breakdown electric field strength of PMMA. Also, unlike PS and PC, the addition of F6TCNNQ to PMMA served to improve the energy density of PMMA capacitors, as additions of 0.01 wt.% and 0.1 wt.% improved the energy density by 9% to 13.51 at an electric field of 780 MV / m and by 20% to 14.94 J / cm3at an electric field of 720 MV / m, respectively. The F6TCNNQ in PMMA system is unique from all other systems presented in this work in that energy density gains were realized despite no significant improvement in the breakdown strength of the capacitor.F6TCNNQ was also found to be incompatible with PS and PC - only capacitors comprising PMMA were operational when F6TCNNQ was included. In general, losses appear to improve when either F4TCNQ, F6TCNNQ, or TMT-TTF are added to PMMA, although there is not a clear trend in how additives improve losses in PMMA capacitors aside from 0.1 wt.% F4TCNQ decreasing losses at all equivalent electric fields up to 770 MV / m. Losses of the best performing PMMA capacitors are 16% or smaller below approximately 550 MV / m before increasing to maximum values of 24% for PMMA with 0.1 wt.% F4TCNQ and 25% for PMMA with 0.1 wt.% F6TCNNQ.

[0102] A generally accepted means of quantifying parameters and confidence limits of dielectric breakdown data is through the use of Weibull analyses. Weibull probability analysis is generally adopted to provide a visual representation of the dielectric breakdown strength distribution and offer insights into the expected lifetime and failure characteristics of a batch of capacitors. Two parameter Weibull analysis is based on the following equation (which repeats equation 5 above):C18703_P18703-02002240.623016

[0103] In Equation 5, / 3, also known as the Weibull modulus, is the slope of the straight line on the Weibull probability plot and gives information about the consistency of the capacitor’s dielectric strength, fj represents the field strength at which 63% of devices are expected to fail and has the same unit as the breakdown field. A high fj value usually indicates a high overall breakdown strength for the capacitor population, which shows a robust dielectric material system.

[0104] Data for the PMMA-based capacitors and tables of the derived parameters for all three polymers are shown in tables S4-S6. Our Weibull analysis results show us that the PS capacitors with additives demonstrated higher breakdown field strength compared to those in the pristine form, based on the 7 results. The device performance of PS w / 0.1 wt.% F4TCNQ ( / ? = 16.65) and PS w / 0.1 wt% TMT-TTF ( / ? = 10.32) capacitors is more uniform / consi stent than that of pristine PS capacitors ( / ? = 9.60). The fj values of the PC additives are also higher than that of pristine PC capacitors, suggesting that the additives play an important role in enhancing the dielectric breakdown strength. F4TCNQ, DBTTF and TMT-TTF all help making the device performance more reproducible, based on the higher [3 values. These results are consistent with the additives functioning as deep traps, intercepting undesired injected charges that could initiate breakdown. For PS and PC, in which the additives had the greater relative effect on dielectric breakdown field, the Weibull analysis is also consistent. For PMMA, while the net energy storage density was higher than for the other two polymers, the breakdown field increments were smaller, and fewer data points were recorded. Nevertheless, the Weibull analysis did show that some breakdown field improvements were obtained from the additives.

[0105] To further determine the effects of small molecule additives on energy density and efficiency in each polymer matrix, the leakage current of each sample was measured along with their frequency-dependent capacitance and corresponding dissipation factor in the range of 100 Hz to 100 kHz for PS-based samples. Typical frequency-dependent behavior of the polymer capacitance is observed in this frequency range, with capacitance very gently decreasing as frequency increases. Likewise, increased losses accompany the decreasing capacitance above 10 kHz as evidenced by the sharp increase in the dissipation factor, which otherwise remains quiteC18703_P18703-02002240.623016 low. In general, greater losses are realized in samples containing small molecule additives at frequencies above 10 kHz, while losses are highly comparable with almost no difference at frequencies below 10 kHz. Leakage currents are generally on the order of hundreds of pA for all samples. While some small molecule additives apparently induced increased leakage current relative to controls, the greatest leakage currents never exceeded 5 nA, with most samples never exceeding 1 nA.

[0106] FIG. 9 illustrates examples of Capacitance and Dissipation Factor as a Function of Frequency for Single Layer Capacitors. In 9A the single layer capacitors comprise Polystyrene Control, in 9B PS with 1 wt.% DBTTF, in 9C PS with 0.1 wt.% F4TCNQ, and 9D PS with 0.1 wt.% TMT-TTF, with each chart showing the capacitance 902, 906, 910, 914 and the dissipation 904, 908, 912, 916.

[0107] In addition to measuring the P-E loops to calculate the energy density and efficiency of the single layer polymer capacitors, 3D surface images of the top surfaces of the films were obtained using a laser optical microscope. These images were obtained to assess the surface morphology and estimate the roughness of each film. It was determined that blending each additive in such dilute concentrations of 0.01 to 1 wt.% had no effect on either the morphology or the roughness of any of the polymer films. The PC film appears to have the greatest roughness and poorest surface morphology of the three polymers, followed closely by the PS film while the PMMA film exhibits ideal capacitor film characteristics of minimal surface roughness and a smooth, homogenous surface morphology. Despite pursuing simple solution processing, all three polymer films are notably clear of surface defects, such as pinholes, that would compromise the performance and integrity of the devices presented in this work.

[0108] Additional structural characterization of the capacitor dielectrics was pursued via XRD, with several XRD patterns for each polymer dielectric material. The polymer control samples exhibit amorphous film characteristics, with little difference exhibited in samples containing small molecule additives. Measurement artifacts are present in several patterns near 32.8° as well as near 18.4° in the PC with 0.01 wt.% F4TCNQ pattern due to the measurement configuration on the diffractometer used to obtain the patterns. These artifacts are not representative of actual diffraction from the small molecule additives, as evidenced by patterns available in the literature. While nearly no differences arise from the inclusion of small moleculeC18703_P18703-02002240.623016 additives in either PS or PMMA, very subtle differences can be observed in the XRD patterns when additives are introduced to PC.

[0109] The investigation considered whether the additives were dispersed in the polymers on the molecular level versus forming observable aggregates or particles. At the low concentrations used in this study, the additives pass through submicron filters and do not seem to form separate domains. The cyanoquino compounds were initially made as solutions near their saturation but then diluted considerably when blending with the polymers. The blend solutions were sonicated extensively and filtered to ensure uniform distribution. Finally, the investigation checked films of key compositions containing higher-melting additives using scanning electron microscopy. For each of the three polymers containing 1% (the higher concentration used) of DBTTF and F4TCNQ, there was no sign of any aggregation or particle formation on the tens of nm size scale. The SEM images appeared smooth and essentially featureless.

[0110] It is clear that the incorporation of the electroactive small molecules DBTTF, F4TCNQ, and TMT-TTF greatly improves the energy density and breakdown strength of PS capacitors, which can be attributed to the ability of these molecules to act as charge traps to suppress conduction pathways and delay dielectric breakdown from occurring. Losses at high fields arise due to TC-JI stacking interactions in PS capacitors due to inherent limitations of the aromatic polymer when used as a capacitor dielectric. However, for electric fields up to 340 MV / m, the loss of PS capacitors is significantly smaller when the electroactive small molecules are included. This indicates that while blended electroactive small molecules serve to improve the breakdown strength and energy density of PS capacitors, further performance increases are limited due to substantial conduction losses induced by 7i-n stacking of the aromatic rings of PS.[OHl] The maximum polarization of PC devices increases more than 50% relative to PS capacitors due to the higher permittivity of PC relative to PS (3 vs 2.6 at 1 kHz, higher for PC at lower frequencies), while the more rigid polymer backbone reduces 71-71 stacking and conduction losses, subsequently improving the breakdown strength by up to 200 MV / m when compared to the PS with 1 wt.% TMT-TTF capacitor and up to 400 MV / m when compared to the PS control capacitor. The absence of aromatic moieties from the polymer backbone serves to greatly enhance the breakdown strength to as large as 850 MV / m, while polarization increases are greater than 100% and 200% relative to the best performing PC and PS capacitors, respectively, due largely to the even greater permittivity of PMMA (in the range of 3-5 depending onC18703_P18703-02002240.623016 frequency). While the losses of PMMA capacitors at high electric fields become relatively large, the significant increases in performance serve as a positive compromise to enhance the applicability of such devices.

[0112] The performance of polymer film capacitors in this work is enhanced using different polymer dielectrics and electroactive small molecules that can trap charges that would otherwise cause dielectric breakdown to occur. As previously mentioned, removing aromatic moieties from the polymer structure and using more rigid polymers leads to a reduction in 71 -7t stacking, reducing conduction loss and enhancing the breakdown electric field strength. The use of DBTTF and F4TCNQ serves to further improve the performance of capacitors through charge trapping, as the ability of DBTTF to trap holes when blended in OFET gate dielectrics was previously demonstrated by the authors’ group, while the electron accepting behavior of F4TCNQ with its high electron affinity is well documented in literature. Even deeper traps to further immobilize free charge carriers are likely introduced using TMT-TTF and F6TCNNQ, which are stronger electron donors and acceptors than DBTTF and F4TCNQ. The reduced losses observed in PC and PMMA systems with F4TCNQ at submaximal fields supports the use of deep traps to suppress avalanche ionization and hinder dielectric breakdown. The frequencydependent capacitance behavior indicates losses are minimized at lower frequencies and agrees with experimental observations of P-E loop acquisition at 10 Hz being more reliable than at 100 Hz. Additionally, increases in hysteresis that accompany increases in polarization for PS and PC samples provide further evidence of charge trapping. The ability of DBTTF to improve performance in PS and PC but not PMMA, while F6TCNNQ was only compatible with PMMA, suggests that polymer-dopant compatibility can play a critical role in determining whether a small molecule dopant can serve to enhance the performance and applicability of a polymer capacitor.

[0113] Efficiency improvements were observed in all doped systems at moderate and submaximal electric fields. For example, PC with 0.01 wt.% F4TCNQ and PC with 1 wt.% TMT-TTF maintained losses below 12% up to 550 MV / m, competitive with many high-performance polymer capacitors. However, at electric fields higher than control capacitor breakdown strength, efficiency declined due to increased conduction losses, especially in PS systems where aromatic 71-71 stacking exacerbated this issue. Tradeoffs between energy density and efficiency in polymer capacitors are well documented in literature, and it has been shownC18703_P18703-02002240.623016 that while high dielectric constants can boost energy density, this often comes with increased dielectric loss. While some of this increased loss can be mitigated through trap engineering and dielectric design, losses in polymer capacitors will generally continue to scale and increase as breakdown strength increases. The maximum energy density of 16.20 J / cm3produced by the PMMA with 0.1 wt.% F4TCNQ capacitor in this work is highly competitive with other all-organic polymer capacitors, while offering simple fabrication and easily scalable processing to further support their applicability.

[0114] In general, limited data are available in the literature for making accurate comparisons between the energy storage performance of capacitors presented in this work with organic capacitor systems containing all-organic filler materials. For example, modification of the PS polymer structure to include 45 mol% methyl methacrylate (MMA) units in a copolymer structure yielded a maximum energy density of 12.2 J / cm3at a breakdown field of 530 MV / m with 92% efficiency, however, neither the PS or PMMA capacitors in this work are suitable comparisons for a PS-MMA copolymer. In the case of PMMA there is a maximum energy density of 16.1 J / cm3with efficiency >90% at a breakdown field of 800 MV / m for a capacitor comprising PMMA blended with pre-copolymerized MMA and vinyl quinoline (VQQ). This exceeds the performance of PMMA capacitors in this experiment, although the PMMA with 0.1 wt.% F4TCNQ system exhibits a highly competitive energy density and breakdown field which could benefit from further design optimization in future work. Design and modification of the chemical structure of polymer dielectrics has yielded the greatest performances, with breakdown fields in excess of 1100 MV / m and energy densities as large as 35 J / cm3. Further comparisons of PC capacitor performances are also difficult to make as most available data was obtained at temperatures greater than 100°C, while devices in this work were tested at room temperature.

[0115] From the polarization data, it appears that the additives can induce 10-20% additional charge storage in polystyrene and somewhat increased hysteresis, while the polystyrene control polarization is in good agreement with the expected value from the permittivity (A 2.5-2.7) x field product. The polycarbonate polarizations per unit field are similar for all the additives with slight increases in hysteresis from the additives. The PMMA samples, except for F6TCNNQ, all show equivalent polarizations per unit field that are in agreement with the permittivity (sr~4.0) x field product, and the additives, with very little if any additional hysteresis from the additives.C18703_P18703-02002240.623016 One-percent of small -molecule, non-plasticizing additives would not be expected to cause an observable change in glass transition temperature obtained from thermograms.

[0116] Further improvements in performance could be achieved by improving the surface roughness of the polymer films, as the low boiling point of chloroform leads to a high surface roughness of spin coated films that negatively impacts performance. Polycarbonate shows far greater surface roughness than PS and PMMA due to slightly poorer solubility in the solvents chosen for this work as well as a higher glass transition temperature that may cause premature aggregation during the spin coating process. Additional reductions in losses can be realized through using gold electrodes on both sides of the thin-film polymer capacitor, as the use of the higher surface roughness ITO as a bottom contact electrode will lead to increased losses in the capacitor in addition to a mismatch in work function between the two electrodes of the capacitor. The higher surface roughness of polycrystalline ITO compared to gold may also contribute to the higher degree of surface roughness observed in the spin-coated polymer fdms.

[0117] XRD patterns indicate no significant changes in the arrangement of any polymer matrix are realized as a result of including small molecule additives, evidenced by the lack of diffraction in any pattern. Likewise, no differences in laser optical micrographs were observed for dielectric blend samples relative to control samples in this work, as the dilute concentration of small molecule additives prevents further structural and morphological characterization.

[0118] The dilute addition of the electroactive small molecules DBTTF, TMT-TTF, F4TCNQ, and F6TCNNQ to single layer polymer capacitors comprising PS, PC, or PMMA serves to enhance their efficiency, breakdown field strength, and maximum energy density. These performance improvements can increase the applicability of solution processible engineering polymers such as PC and PMMA for use in capacitors, which are typically disregarded due to suboptimal performance and high energy losses at moderate electric fields. This work can be extended to numerous electroactive small molecules and polymer dielectrics that are solution processable. The chemical structure of polymer dielectrics can also be functionalized to tether electroactive substituents to their backbone and include cross-linkable functional groups to enable the development of multilayer capacitors with alternating layers of different electroactive molecules.

[0119] C18703_P18703-02002240.623016

[0120] FIG. 10 illustrates a method embodiment for manufacturing a capacitor. As illustrated, the method includes: providing a polymer solution comprising a polymer dielectric dissolved in an organic solvent (1002); providing an additive dispersion comprising a particle additive selected from inorganic semiconductor particles or oxidizable or reducible organic molecular solids (1004); combining the additive dispersion with the polymer solution to form a composite dielectric solution, wherein the additive is present in an amount between 1 and 10,000 parts per million by weight relative to polymer in the composite dielectric solution (1006); agitating the composite dielectric solution to distribute the particle additive substantially uniformly within the polymer solution (1008); depositing the composite dielectric solution onto a first electrode to form a dielectric layer (1010); removing solvent from the dielectric layer to form a solid composite dielectric film (1012); and forming a second electrode spaced apart from the first electrode with the solid composite dielectric film disposed therebetween (1014).

[0121] In some configurations, depositing the composite dielectric solution comprises spin coating the composite dielectric solution onto the first electrode at a rotational speed between 500 rpm and 3000 rpm to form a film having a thickness between 1 pm and 5 pm.

[0122] In some configurations, removing solvent comprises heating the dielectric layer at a temperature between 50 °C and 200 °C under reduced pressure for at least 30 minutes.

[0123] In some configurations, the illustrated method can further include: filtering the composite dielectric solution through a filter having a pore size of 0.1 pm to 1.0 pm prior to depositing the composite dielectric solution.

[0124] In some configuraitons, the particle additive comprises particles having a characteristic dimension greater than 10 nm and less than 10 pm.

[0125] In some configurations, the particle additive comprises at least one of nickel oxide particles, zinc selenide particles, dibenzotetrathiafulvalene particles, or tetrafluorotetracyanoquinodimethane particles.

[0126] In some configurations, providing the polymer solution comprises dissolving a hydrocarbon polymer or an oxygenated polymer in a halogenated organic solvent to form a homogeneous solution prior to combining with the additive dispersion.

[0127] In some configurations, the illustrated method can further include: forming a second dielectric layer on the solid composite dielectric film prior to forming the second electrode,C18703_P18703-02002240.623016 wherein the second dielectric layer comprises a crosslinked polymer dielectric to form a multilayer capacitor structure.

[0128] Use of language such as “at least one of X, Y, and Z,” “at least one of X, Y, or Z,” “at least one or more of X, Y, and Z,” “at least one or more of X, Y, or Z,” “at least one or more of X, Y, and / or Z,” or “at least one of X, Y, and / or Z,” are intended to be inclusive of both a single item (e.g., just X, or just Y, or just Z) and multiple items (e.g., {X and Y}, {X and Z}, {Y and Z}, or {X, Y, and Z }). The phrase “at least one of’ and similar phrases are not intended to convey a requirement that each possible item must be present, although each possible item may be present.

[0129] The various embodiments described above are provided by way of illustration only and should not be construed to limit the scope of the disclosure. Various modifications and changes may be made to the principles described herein without following the example embodiments and applications illustrated and described herein, and without departing from the spirit and scope of the disclosure. For example, unless otherwise explicitly indicated, the steps of a process or method may be performed in an order other than the example embodiments discussed above. Likewise, unless otherwise indicated, various components may be omitted, substituted, or arranged in a configuration other than the example embodiments discussed above.

[0130] Further aspects of the present disclosure are provided by the subject matter of the following clauses.

[0131] A composite dielectric for capacitors, comprising: a polymer dielectric; and a particle additive distributed substantially uniformly in the polymer dielectric, wherein the particle additive is in a relative amount of between 1 and 10,000 parts per million to polymers therein; and wherein the particle additive is capable of trapping at least one of hole charges or electron charges in the polymer dielectric.

[0132] The composite dielectric according to any preceding clause, wherein the particle additive comprises particles that are less than 10 pm and greater than 10 nm.

[0133] The composite dielectric according to any preceding clause, wherein particles of the particle additive comprise compound inorganic semiconductors, or oxidizable organic molecular solids, or reducible organic molecular solids.

[0134] The composite dielectric according to any preceding clause, wherein the inorganic semiconductors comprise at least one of nickel oxide or zinc selenide.C18703_P18703-02002240.623016

[0135] The composite dielectric according to any preceding clause, wherein the reducible organic molecular solids and the oxidizable organic molecular solids comprise at least one of a tetrathiafulvalene or tetracyanoquinoid ring system.

[0136] The composite dielectric according to any preceding clause, wherein the reducible organic molecular solids and the oxidizable organic molecular solids comprise at least one of dibenzotetrathiafulvalene (DBTTF), tetrakis(methylthio)tetrathiafulvalene (TMT-TTF), tetrafluorotetracyanoquinodimethane (F4TCNQ), or hexafluorotetracyanonaphthoquinodimethane (F6TCNNQD).

[0137] The composite dielectric according to any preceding clause, wherein the reducible organic molecular solids are at least partially dissolved in the polymer of the composite.

[0138] The composite dielectric according to any preceding clause, wherein particles of the particle additive comprise at least one block of a multiblock copolymer.

[0139] The composite dielectric according to any preceding clause, wherein particles of the particle additive are encapsulated by non-particle material.

[0140] The composite dielectric according to any preceding clause, wherein at least some of the polymers are crosslinked.

[0141] The composite dielectric according to any preceding clause, wherein the polymers comprise two or more distinct layers of polymer or polymer composite.

[0142] The composite dielectric according to any preceding clause, wherein one or more layers of the two or more distinct layers comprises particle additive with oxidizing or electrontrapping activity, and wherein one or more layers of the two or more distinct layers comprises particle additive with reducing or hole-trapping activity.

[0143] The composite dielectric according to any preceding clause, wherein the polymers have glass transition temperatures exceeding 150 degrees Celsius.

[0144] The composite dielectric according to any preceding clause, wherein the polymers are hydrocarbon polymers or oxygenated polymers.

[0145] The composite dielectric according to any preceding clause, wherein the hydrocarbon polymers are polystyrenes.

[0146] The composite dielectric according to any preceding clause, wherein the oxygenated polymers are at least one of polycarbonates or polymethacrylates.C18703_P18703-02002240.623016

[0147] A capacitor comprising: a first electrode; a second electrode spaced apart from the first electrode; and a layer of a composite dielectric according to any one of the preceding clauses disposed between the first and second electrodes.

[0148] The capacitor according to any preceding clause, further comprising a second layer of a dielectric material disposed between the first and second electrodes.

[0149] The capacitor according to any preceding clause, further comprising a plurality of layers of dielectric materials disposed between the first and second electrodes.

[0150] A method of manufacturing a capacitor, comprising: providing a polymer solution comprising a polymer dielectric dissolved in an organic solvent; providing an additive dispersion comprising a particle additive selected from inorganic semiconductor particles or oxidizable or reducible organic molecular solids; combining the additive dispersion with the polymer solution to form a composite dielectric solution, wherein the particle additive is present in an amount between 1 and 10,000 parts per million by weight relative to polymer in the composite dielectric solution; agitating the composite dielectric solution to distribute the particle additive substantially uniformly within the polymer solution; depositing the composite dielectric solution onto a first electrode to form a dielectric layer; removing solvent from the dielectric layer to form a solid composite dielectric film; and forming a second electrode spaced apart from the first electrode with the solid composite dielectric film disposed therebetween.

[0151] The method of any preceding clause, wherein depositing the composite dielectric solution comprises spin coating the composite dielectric solution onto the first electrode at a rotational speed between 500 rpm and 3000 rpm to form a film having a thickness between 1 pm and 5 pm.

[0152] The method according to any preceding clause, wherein removing solvent comprises heating the dielectric layer at a temperature between 50 °C and 200 °C under reduced pressure for at least 30 minutes.

[0153] The method according to any preceding clause, further comprising: filtering the composite dielectric solution through a filter having a pore size of 0.1 pm to 1.0 pm prior to depositing the composite dielectric solution.

[0154] The method according to any preceding clause, wherein the particle additive comprises particles having a characteristic dimension greater than 10 nm and less than 10 pm.C18703_P18703-02002240.623016

[0155] The method according to any preceding clause, wherein the particle additive comprises at least one of nickel oxide particles, zinc selenide particles, dibenzotetrathiafulvalene particles, or tetrafluorotetracyanoquinodimethane particles.

[0156] The method according to any preceding clause, wherein providing the polymer solution comprises dissolving a hydrocarbon polymer or an oxygenated polymer in a halogenated organic solvent to form a homogeneous solution prior to combining with the additive dispersion.

[0157] The method according any preceding clause, further comprising: forming a second dielectric layer on the solid composite dielectric fdm prior to forming the second electrode, wherein the second dielectric layer comprises a crosslinked polymer dielectric to form a multilayer capacitor structure.

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Claims

C18703_P18703-02002240.623016 CLAIMSWe claim:

1. A composite dielectric for capacitors, comprising:a polymer dielectric; anda particle additive distributed substantially uniformly in the polymer dielectric, wherein the particle additive is in a relative amount of between 1 and 10,000 parts per million to polymers therein; andwherein the particle additive is capable of trapping at least one of hole charges or electron charges in the polymer dielectric.

2. The composite dielectric according to claim 1, wherein the particle additive comprises particles that are less than 10 pm and greater than 10 nm.

3. The composite dielectric according to claim 1, wherein particles of the particle additive comprise compound inorganic semiconductors, or oxidizable organic molecular solids, or reducible organic molecular solids.

4. The composite dielectric according to claim 3, wherein the inorganic semiconductors comprise at least one of nickel oxide or zinc selenide.

5. The composite dielectric according to claim 3, wherein the reducible organic molecular solids and the oxidizable organic molecular solids comprise at least one of a tetrathiafulvalene or tetracyanoquinoid ring system.

6. The composite dielectric according to claim 3, wherein the reducible organic molecular solids and the oxidizable organic molecular solids comprise at least one of dibenzotetrathiafulvalene (DBTTF), tetrakis(methylthio)tetrathiafulvalene (TMT-TTF), tetrafluorotetracyanoquinodimethane (F4TCNQ), or hexafluorotetracyanonaphthoquinodimethane (F6TCNNQD).C18703_P18703-02002240.623016 7. The composite dielectric according to claim 3, wherein the reducible organic molecular solids are at least partially dissolved in the polymer of the composite.

8. The composite dielectric according to claim 1, wherein particles of the particle additive comprise at least one block of a multiblock copolymer.

9. The composite dielectric according to claim 1, wherein particles of the particle additive are encapsulated by non-particle material.

10. The composite dielectric according to claim 1, wherein at least some of the polymers are crosslinked.

11. The composite dielectric according to claim 1, wherein the polymers comprise two or more distinct layers of polymer or polymer composite.

12. The composite dielectric according to claim 11, wherein one or more layers of the two or more distinct layers comprises particle additive with oxidizing or electron-trapping activity, and wherein one or more layers of the two or more distinct layers comprises particle additive with reducing or hole-trapping activity.

13. The composite dielectric according to claim 1, wherein the polymers have glass transition temperatures exceeding 150 degrees Celsius.

14. The composite dielectric according to claim 1, wherein the polymers are hydrocarbon polymers or oxygenated polymers.

15. The composite dielectric according to claim 14, wherein the hydrocarbon polymers are polystyrenes.

16. The composite dielectric according to claim 14, wherein the oxygenated polymers are at least one of polycarbonates or polymethacrylates.C18703_P18703-02002240.62301617. A capacitor compri sing :a first electrode;a second electrode spaced apart from the first electrode; anda layer of a composite dielectric according to any one of claims 1-16 disposed between the first and second electrodes.

18. The capacitor according to claim 17, further comprising a second layer of a dielectric material disposed between the first and second electrodes.

19. The capacitor according to claim 17, further comprising a plurality of layers of dielectric materials disposed between the first and second electrodes.

20. A method of manufacturing a capacitor, comprising:providing a polymer solution comprising a polymer dielectric dissolved in an organic solvent;providing an additive dispersion comprising a particle additive selected from inorganic semiconductor particles or oxidizable or reducible organic molecular solids;combining the additive dispersion with the polymer solution to form a composite dielectric solution, wherein the particle additive is present in an amount between 1 and 10,000 parts per million by weight relative to polymer in the composite dielectric solution;agitating the composite dielectric solution to distribute the particle additive substantially uniformly within the polymer solution;depositing the composite dielectric solution onto a first electrode to form a dielectric layer;removing solvent from the dielectric layer to form a solid composite dielectric film; and forming a second electrode spaced apart from the first electrode with the solid composite dielectric film disposed therebetween.C18703_P18703-02002240.623016 21. The method of claim 20, wherein depositing the composite dielectric solution comprises spin coating the composite dielectric solution onto the first electrode at a rotational speed between 500 rpm and 3000 rpm to form a film having a thickness between 1 pm and 5 pm.

22. The method according to claim 20, wherein removing solvent comprises heating the dielectric layer at a temperature between 50 °C and 200 °C under reduced pressure for at least 30 minutes.

23. The method according to claim 20, further comprising:filtering the composite dielectric solution through a filter having a pore size of 0.1 pm to 1.0 pm prior to depositing the composite dielectric solution.

24. The method according to claim 20, wherein the particle additive comprises particles having a characteristic dimension greater than 10 nm and less than 10 pm.

25. The method according to claim 20, wherein the particle additive comprises at least one of nickel oxide particles, zinc selenide particles, dibenzotetrathiafulvalene particles, or tetrafluorotetracyanoquinodimethane particles.

26. The method according to claim 20, wherein providing the polymer solution comprises dissolving a hydrocarbon polymer or an oxygenated polymer in a halogenated organic solvent to form a homogeneous solution prior to combining with the additive dispersion.

27. The method according to claim 20, further comprising:forming a second dielectric layer on the solid composite dielectric film prior to forming the second electrode, wherein the second dielectric layer comprises a crosslinked polymer dielectric to form a multilayer capacitor structure.

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