Dielectric Polymer Research Articles

Insulator-donor electron wavefunction coupling in pseudo-bilayer organic solar cells achieving a certificated efficiency of 19.18%

Abstract The incorporation of polymeric insulators has led to notable achievements in the field of organic semiconductors. By altering the blending concentration, polymeric insulators exhibit extensive capabilities in regulating molecular configuration, film crystallinity, and mitigation of defect states. However, current research suggests that the improvement in such physical properties is primarily attributed to the enhancement of thin film morphology, an outcome that seems to be an inevitable consequence of incorporating insulators. Herein, we report a general and completely new effect of polymeric insulators in organic semiconductors: the insulator-donor electron wavefunction coupling effect. Such insulators can couple with donor polymers to reduce the energy barrier level and facilitate the intramolecular electron transport. Besides the morphological effects, we observed that this coupling effect is another mechanism that can significantly enhance the electron mobility (up to 100 times) through the incorporation of polymeric insulators in a series of donor systems. With this effect, we proposed a polymeric insulator blending approach to fabricate state-of-the-art pseudo-bilayer organic solar cells, and the PM6/L8-BO device exhibits a high efficiency of 19.50% (certificated 19.18%) with the improved interfacial electron transport property. This work not only offers a novel perspective on the quantum effect of polymeric insulators in organic semiconductors, but also presents a simple yet effective method for enhancing the performance of organic solar cells.

Scalable all polymer dielectrics with self-assembled nanoscale multiboundary exhibiting superior high temperature capacitive performance

Polymers are key dielectric materials for energy storage capacitors in advanced electronics and electric power systems due to their high breakdown strengths, low loss, great reliability, lightweight, and low cost. However, their electric and dielectric performance deteriorates at elevated temperatures, making them unable to meet the rising demand for harsh-environment electronics such as electric vehicles, renewable energy, and electrified transportation. Here, we present an all-polymer nanostructured dielectric material that achieves a discharged energy density of 7.1 J/cm³ with a charge-discharge efficiency of 90% at 150°C, outperforming the existing dielectric polymers and representing more than a twofold improvement in discharged energy density compared with polyetherimide. The self-assembled nano-scale multiboundaries effectively impede the charge injection and excitation, leading to more than one order of magnitude lower leakage current density than the pristine polymer matrix PEI at high electric fields and elevated temperature. In addition, the film processing is simple, straightforward, and low cost, thus this all-polymer nanostructured dielectric material strategy is suitable for the mass production of dielectric polymer films for high-temperature capacitive energy storage.

Remarkably boosted high-temperature energy storage of a polymer dielectric induced by polymethylsesquioxane microspheres.

Polymer dielectrics are the key materials in next-generation electrical power systems. However, they usually suffer from dramatic deterioration of capacitive performance at high temperatures. In this work, we demonstrate that polymethylsesquioxane (PMSQ) microspheres with a unique organic-inorganic hybrid structure can remarkably enhance the energy storage performance of a typical high-temperature dielectric polymer polyetherimide (PEI). Compared with traditional ceramic fillers, there exists -CH3 on the surface of PMSQ microspheres, which results in good compatibility between PMSQ and PEI. In addition, the PMSQ microspheres with excellent insulating properties can effectively block the charge transport, yielding significantly enhanced breakdown and energy storage performance. Consequently, the PEI based composite film with 5 wt% PMSQ microspheres exhibits ultrahigh energy storage densities of 12.83 J cm-3 and 9.40 J cm-3 with an efficiency (η) above 90% at 150 °C and 200 °C, respectively, which are 10.5 and 50.5 times those of the pure PEI film. This work demonstrates that microspheres with an organic-inorganic hybrid structure are excellent candidates for enhancing the high-temperature performance of polymer dielectrics, and these PMSQ/PEI composite films have huge potential for application in high-temperature film capacitors.

Ultrahigh Energy Storage of Twisted Structures in Supramolecular Polymers.

Polymer dielectrics possess outstanding advantages for high-power energy storage applications such as high breakdown strength (Eb) and efficiency (η), while both of them decrease rapidly at elevated temperatures. Although several strategies have been evaluated to enhance Eb and heat resistance, the discharged energy density (Ud) is still limited by the planar conjugated structure. In this study, a novel approach to manipulate polymer morphology is introduced, thereby influencing dielectric properties. A range of polyurea (PU)-based polymers are predicted from different structural unit combinations by machine learning and synthesized two representative polymers with high dielectric constants (K) and thermal stability. These polymers are combined with PI to form a twisted polymer via hydrogen bonding interactions (HNP). Both experimental results and computational simulations demonstrate the twisted structure disrupts the conjugated structure to widen the bandgap and increase dipole moment through the twisting of polar groups, leading to simultaneous improvements in both K and Eb. Consequently, HNP-20% achieves an ultrahigh Ud of 6.42 Jcm-3 with an efficiency exceeding 90% at 200 °C. This work opens a new avenue to scalable high Ud all-polymer dielectric for high-temperature applications.

Green synthesis of boehmite-reinforced cashew gum/polypyrrole biopolymer blend for advanced biomaterials

Electrically conducting biopolymer blend nanocomposites based on different contents of boehmite (BHM) reinforced cashew gum (CG) /polypyrrole (PPy) blend is synthesized by an in situ polymerization technique using water as a green solvent. The resulting bio-blend nanocomposites underwent comprehensive analysis concerning their structural, morphology, thermal, and electrical properties, such as dielectric constant, dielectric loss, electric modulus, and AC conductivity. The Fourier transform infrared spectroscopy (FTIR) spectra revealed the presence of metal oxide stretching in the blended nanocomposite at 512 cm−1. Field emission scanning electron microscopy (FE-SEM) confirmed the attachment and uniform dispersion of BHM within the CG/PPy blend at 7 wt% loading, and beyond this loading, the nanoparticles get agglomerated in the biopolymer blend. The glass transition temperature and thermal stability of all the blended nanocomposites are higher than that of the pure CG/PPy blend and these thermal properties increase with the loading of nanoparticles. Conductivity experiments demonstrated that as the nanofiller content increases up to 7 wt%, there is a concurrent rise observed in AC conductivity, dielectric loss, and dielectric constant. There is a substantial difference of 1.21 Scm−1 between the maximum and minimum AC electrical conductivity, at 102 Hz. However, a decrease in electrical properties is observed at the highest loadings of BHM due to the agglomeration of nanoparticles in the polymer blend matrix. The lowest activation energy value (0.049 × 10−4 eV) is also exhibited by 7 wt% BHM nanocomposites. Furthermore, the electrical properties of both CG/PPy and CG/PPy/BHM nanocomposites exhibited a temperature-dependent behavior, progressively increasing until reaching maximum values. This study suggests that such bio-based polymer dielectrics could be promising materials for various applications, offering enhanced thermal and electrical properties through careful control of nanofiller content and dispersion.

Effect of thermal shock on energy density of biaxially oriented polypropylene films for pulsed power capacitors

In this paper, thermal shock experiments are performed on the biaxially oriented polypropylene (BOPP) films, and the changes in dielectric and energy storage properties before and after the experiments are explored. The experimental results show that the films have reduced comprehensive performance with the thermal shock time and frequency increasing. After the thermal shock, both the permittivity and the dielectric loss increase slightly. And, the direct current (DC) conductivity has risen by 73.6%–714.2%. The lowest DC breakdown strength of film is 604.4 kV mm−1, showing a 13.5% reduction compared to that of pristine film. In addition, energy storage performance has also deteriorated. The maximum discharge energy density decreased from 4.62 J cm−3 of pristine film to 3.26 J cm−3 of treated film. There is a decrease in charge and discharge efficiency under the same electric field. The metallization layer of the film receives less influence; the capacitance is reduced by only 0.37%. The causes and mechanisms of performance changes are analyzed and discussed. The disruption of molecular chains during thermal shock is the most important factor leading to the degradation of films. This paper provides a powerful perspective and reference for studying the performance degradation and failure of polymer dielectrics under extreme operating conditions.

Alicyclic Polyimide With Multiple Breakdown Self-Healing Based on Gas-Condensation Phase Validation for High Temperature Capacitive Energy Storage.

Polymer dielectrics with combined thermal stability and self-healing properties are specifically desired for high-temperature film capacitors. The high thermal stability of conventional polymers benefits from the abundance of aromatic rings in the molecule backbone, but the high carbon content sacrifices their self-healing properties. Here, analicyclic polyimide with a high glass transition temperature (256°C) and wide energy bandgap (4.58eV) is designed, which exhibits electric conductivity more than an order of magnitude lower than that of classical polyimide at high electric fields and high temperatures. As a result, alicyclic polyimide achieves a discharged energy density of 4.54 Jcm-3 and a charge-discharge efficiency of above 90% at 200°C, which is superior to existing dielectric polymers and composites. The alicyclic polyimide benefits from a low pyrolytic residual carbon rate, retaining 93% of the dielectric breakdown strength after four electrical breakdown cycles. Distinguishing from the current condensed-phase self-healing concept, for the first time, exploring the self-healing capability of high-temperature polyimide dielectric is presented based on dual self-healing mechanisms of gas-phase and condensed-phase. The high energy density at high temperatures and the superior self-healing capability of alicyclic polyimide further indicate the promise of polyimide dielectric film capacitors for extreme conditions.

Failure evaluation of outdoor polymeric insulators based on statistical condition-assessment methods

Field aging of outdoor polymeric insulators results in unscheduled outages in power systems particularly in harsh climate conditions. In this paper, a strategic maintenance framework is proposed in order to prevent overhead line outages. The presented scheme is based on condition assessment of the real aged polymeric insulators. Data of tensile test, hardness test, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) are used to extract critical features of the aged samples based on classification of fuzzy c-means clustering. Then, a lifetime prediction analysis is done based on Cox hazards analysis to develop further maintenance strategy. The proposed model is validated through numerical analyses on polymeric insulators for various validation evaluations including pollution severity analysis and hydrophobicity class (HC) measurement. Obtained results verify accuracy of the intelligent model to predict lifetime of the aged polymeric insulators. The presented strategic framework can be effectively applied to online monitoring, condition assessment and preventive maintenance programs of the power system utilities.

Quasi-Hydrogen Bond and Charge-Trapping Effect Originating from Polar Side Group Lead to Significantly Suppressed Charge Transport in Polypropylene.

How to fundamentally suppress charge transport is one of the essential issues in polymer dielectrics. This work reports significant charge transport suppression by glycidyl methacrylate (GMA) side group modification on polypropylene (PP). Experimental and computational investigations discover for the first time a quasi-hydrogen bond effect generated by carbonyl and epoxide of GMA in PP inter/intramolecular structure, while introducing trap energy levels within the HOMO-LUMO gap. These energy levels suppress the leakage current of GMA-modified PP thanks to the charge-trapping effect. The quasi-hydrogen bond originating from the interaction between the high-polar GMA group and flexible PP chain raises the thermostability while averaging the electron distribution between hydrogen and acceptor oxygen, which is conducive to lessening electric weak points, suppressing charge transport, and finally enhancing the electrical breakdown strength. This work provides new thinking on polymer dielectric design and charge transport regulation utilizing electron structure and weak interaction at the molecular scale.

Enhanced high-temperature energy storage performances in polymer dielectrics by synergistically optimizing band-gap and polarization of dipolar glass

Polymer dielectrics play an irreplaceable role in electrostatic capacitors in modern electrical systems, and have been intensively studied with their polarization and breakdown strength (Eb) optimized for high discharged energy density (Ud) at elevated temperatures. Small molecules have been explored as fillers, yet they deteriorate thermal stability of matrix which limits their optimal loading to ~1 wt%. Herein, we develop a polymer blend dielectric consisting of common polyimide and a bifunctional dipolar glass polymer which are synthesized from two small molecule components with wide band-gap and large dipole moment. The bifunctional dipolar glass with large molecular weight not only maintains thermal stability of polymer blends even at a high loading of 10 wt%, but also induces substantial enhancement in polarization and Eb than any of individual components does, achieving an ultrahigh Ud of 8.34 J cm−3 (150 °C) and 6.21 J cm−3 (200 °C) with a charge-discharge efficiency of 90%.

High-Density Capacitive Energy Storage in Low-Dielectric-Constant Polymer PMMA/2D Mica Nanofillers Heterostructure Composite

The ubiquitous, rising demand for energy storage devices with ultra-high storage capacity and efficiency has drawn tremendous research interest in developing energy storage devices. Dielectric polymers are one of the most suitable materials used to fabricate electrostatic capacitive energy storage devices with thin-film geometry with high power density. In this work, we studied the dielectric properties, electric polarization, and energy density of PMMA/2D Mica nanocomposite capacitors where stratified 2D nanofillers are interfaced between the multiple layers of PMMA thin films using two heterostructure designs of the capacitors, PMMA/2D Mica/PMMA (PMP) and PMMA/2D Mica/PMMA/2D Mica/PMMA (PMPMP). The incorporation of a 2D Mica nanofiller in the low-dielectric-constant PMMA leads to an enhancement in the dielectric constant, with ∆ε ~ 15% and 53% for PMP and PMPMP heterostructures at room temperature. Additionally, a significant improvement in discharged energy density was measured for the PMPMP capacitor (Ud ~ 38 J/cm3 at 825 MV/m) compared to the pristine PMMA (Ud ~ 9.5 J/cm3 at 522 MV/m) and PMP capacitors (Ud ~ 19 J/cm3 at 740 MV/m). This excellent capacitive and energy storage performance of the PMMA/2D Mica heterostructure nanocomposite may inform the fabrication of thin-film, high-density energy storage capacitor devices for potential applications in various platforms.

Field-dependent nonlinear electrical response characteristics in polymer dielectrics with sodium alginate scaffold

Field-dependent nonlinear electrical response characteristics in polymer dielectrics with sodium alginate scaffold

Experimental and Modeling Investigation of the Temperature Activation of TDDB in Galvanic Isolators Based on Polymeric Dielectrics

Experimental and Modeling Investigation of the Temperature Activation of TDDB in Galvanic Isolators Based on Polymeric Dielectrics

Enhancement of High-Temperature Breakdown Strength by Annealing Dielectric Polymers Near Melting Points

Enhancement of High-Temperature Breakdown Strength by Annealing Dielectric Polymers Near Melting Points

Enhanced energy storage capability of hydroxylated BiFeO3/PVDF composites designed by compositionally gradient multilayer structures

With the development of the microelectronics industry, there is a huge demand for flexible polymer dielectrics with excellent dielectric energy storage capacity, aimed at increasing dielectric constant and enhancing breakdown strength. In this study, the hydroxylated BiFeO3-loaded polyvinylidene fluoride(PVDF) composite films were prepared by electrostatic spinning techniques and the energy storage properties have been investigated. The results show that the dielectric constant and breakdown strength of the composites are effectively influenced by the hydroxylation modification and spatial structure. More interestingly, the seven-grade hydroxylated composite films exhibit a great enhancement of the excellent energy storage performances (Ue, ∼13.21 J/cm3; η, ∼66.2 %). This study demonstrates the immense potential of these composites as highly efficient dielectric materials suitable for use in energy storage capacitors.

Roll-to-Roll Manufactured Polyetherimide Nanocomposite With Different Diameters of SiO2 Nanoparticles Exhibiting Improved High-Temperature Dielectric Energy Storage Performance.

To enhance the high-temperature energy storage performance of the polymer-based dielectric film, inorganic nanofillers with large band gaps are much more effective and have been widely adopted. However, the impact of nanoparticle diameters on the dielectric properties of polymer nanocomposites has been less studied. Herein, silicon dioxide nanoparticles (SiO2-NPs)with varying diameters (20, 60, 120, 200nm) prepared by the sol-gel method are incorporated in the PEI matrix to form PEI/SiO2 nanocomposites. The characterization results reveal a distinct correlation between the dielectric properties of polyetherimide (PEI) composites and the diameters of SiO2-NPs. Leakage current density analysis and breakdown strength simulations indicate that SiO2-NPs with smaller diameters generate more deep traps that impede the transport of charge carriers, especially under high temperatures. Notably, PEI/20nm-SiO2 exhibits a high discharged energy density of 4.4 J cm-3 with an efficiency of 90% at 150°C. Furthermore, PEI/SiO2 films with 10µm in thickness are manufactured by a large-scale solution casting process. The continuously prepared PEI/20nm-SiO2 film exhibits a discharged energy density of 3.2 J cm-3 with an efficiency of 90% at 150°C. This study not only provides a strategy for the design of high-performance dielectric polymer composites but also offers a large-scale high-temperature dielectric film for practical use.

Study on the Effect of Electron/Hole Injection on the Energy-Storage Properties of Polymer Dielectrics.

As a critical component of electrostatic capacitors, the polymer dielectric directly affects the performance of the capacitor. In this work, Polycarbonate (PC)/Polyvinylidene fluoride (PVDF) asymmetric bilayer polymer dielectrics were prepared, and the influence of different polymer materials' barrier characteristics on various electrical properties of composite dielectrics was studied by changing the direction of applied electric fields. Research has found that the dielectric constant of a composite dielectric is between PVDF and PC (approximately 4.8 at 10 Hz) and is independent of the relative position of PVDF and PC in the dielectric. However, the relative position of PC and PVDF has a significant impact on the energy-storage characteristics of composite dielectrics. When PVDF comes into contact with the negative electrode, even though PC has a higher hole barrier, the composite dielectric can only withstand a maximum electric-field strength of 400 MV/m, which is much lower than the maximum electric-field strength that pure PC can withstand (520 MV/m), and it only achieves an energy-storage density of 3.7 J/cm3. When the PC comes into contact with the negative electrode, the high electron barrier of the PC effectively suppresses the injection of electrons at the electrode. It can withstand the same electric-field strength as PC (520 MV/m), achieving an energy-storage density of 5.48 J/cm3, which is 1.46 times that of pure PC and 1.64 times that of PVDF. This experiment effectively combined the advantages of PC and PVDF by utilizing the electron/hole barrier of polymer materials to obtain a fully organic dielectric with excellent energy-storage performance.

Recyclable Polymeric Cable Insulation Materials: A Comprehensive Review

Recyclable Polymeric Cable Insulation Materials: A Comprehensive Review

Enhancing dielectric property and multi-interface polarization of poly(vinylidene fluoride)/Ni-embedded CaCu3Ti4O12 fibers composites tailored by magnetic field

In the realm of advanced electrical equipment and systems, polymer nanocomposites possess significant application value due to their excellent dielectric properties. Metal@ceramic fillers with a core-shell structure can enhance the dielectric constant (ε′) of polymer nanocomposites; however, their application is limited by the high dielectric loss (tanδ). A magnetic field tailoring strategy is introduced in this article to significantly improve the dielectric properties of poly(vinylidene fluoride) (PVDF) composites. Magnetic CaCu3Ti4O12–Ni (CN) composite fibers are formed by embedding Ni nanoparticles within CaCu3Ti4O12 (CCTO) fibers. Furthermore, the CN fibers are horizontally orientated in the PVDF matrix by tailoring the optimal magnetic field to 1.0 T–150 ℃. This results in a significant increase in the ε′ of 25, which is 92 % and 194 % higher than that of a CN fiber without magnetic field treatment and pure PVDF, respectively, while maintaining a low tanδ of 0.08. Experimental and simulation results indicate that the magnetic orientation tailoring enhances the multi-interface polarization, especially the inner interfacial polarization (△Pin) at the CCTO/Ni interfaces, dominantly improving dielectric performance, as evidenced by the high interfacial polarization strength, △ε2 ∼ 141.51, the low activation energy, Ea ∼ 0.81 eV, and the large △Pin ∼ 1.06×104 μC/m2. This magnetic orientation tailoring strategy offers a new paradigm and significant guidance for the development of polymer dielectrics with exceptional dielectric properties.

Functional Zwitterionic Polyurethanes as Gate Dielectrics for Organic Field‐Effect Transistors

AbstractThe development of polymeric dielectrics with a high dielectric constant is of great significance for flexible low‐voltage organic field‐effect transistors (OFETs). Herein, functional polyurethanes (PUs) with nitro and sulfobetaine zwitterionic groups are synthesized, and their electrical properties, mechanical properties, and the performances of OFET devices using these zwitterionic PUs as gate dielectrics are studied. Compared with sulfobetaine zwitterion‐containing PUs, nitro‐containing PUs (NO2‐PUs) show higher dielectric constant up to 6.5. Both zwitterionic PUs enhance the OFET performances, while the effect of NO2‐PU is more significant. Devices using NO2‐PU‐15 that contains 15 moL% nitro groups as the dielectric layer show the best performance and a threshold voltage (Vth) of as low as −0.02 V together with two orders’ increase of the mobility is observed, compared with the devices using PU without nitro groups. This study provides a new method to improve the dielectric constant of polymeric dielectrics, which is valuable for flexible/stretchable and wearable electronic devices.