Exploration on the P(VP-co-VAc) copolymer based gel polymer electrolytes doped with quaternary ammonium iodide salt for DSSC applications: Electrochemical behaviors and photovoltaic performances

Gel polymer electrolytes (GPEs) consisting of poly(1-vinylpyrrolidone-co-vinyl acetate) P(VP-co-VAc) with the different tetrapropylammonium iodide (TPAI) salt concentration are prepared. The dielectric and electric dispersion behaviors of the GPEs are studied by dielectric relaxation spectroscopy at room temperature. The dielectric studies imply that dielectric constant (ε′) and dielectric loss (ε″) values decrease with increase in frequency at lower frequency region whereas frequency independent behavior is observed in the high frequency region. The trend of the dispersion part of the electric modulus shows a shift towards higher region of frequency indicating shorter relaxation time with an increase in TPAI concentration. The GPE samples were observed to obey Arrhenius behavior and the highest ionic conductivity obtained is 1.60 × 10⁻³ S cm⁻¹ at room temperature. The GPE samples are then fabricated into dye sensitized solar cells for photovoltaic studies. Highest efficiency of 3.07% is obtained with short circuit current density of 6.86 mA cm⁻², open circuit voltage of 727 mV and fill factor of 62%.     

Ultrahigh Energy Density of Antiferroelectric PbZrO3-Based Films at Low Electric Field

Dielectric capacitors play a vital role in advanced electronics and power systems as a medium of energy storage and conversion. Achieving ultrahigh energy density at low electric field/voltage, however, remains a challenge for insulating dielectric materials. Taking advantage of the phase transition in antiferroelectric (AFE) film PbZrO₃ (PZO), a small amount of isovalent (Sr²⁺) / aliovalent (La³⁺) dopants are introduced to form a hierarchical domain structure to increase the polarization and enhance the backward switching field E_A simultaneously, while maintaining a stable forward switching field E_F. An ultrahigh energy density of 50 J cm⁻³ is achieved for the nominal Pb_0.925La_0.05ZrO₃ (PLZ5) films at low electric fields of 1 MV cm⁻¹, exceeding the current dielectric energy storage films at similar electric field. This study opens a new avenue to enhance energy density of AFE materials at low field/voltage based on a gradient-relaxor AFE strategy, which has significant implications for the development of new dielectric materials that can operate at low field/voltage while still delivering high energy density.     

High-performance Poly(biphenyl piperidinium) Type Anion Exchange Membranes with Interconnected Ion Transfer Channels: Cooperativity of Dual Cations and Fluorinated Side Chains

The performance of alkaline fuel cells is severely limited by substandard anion exchange membranes (AEMs) due to the lower ionic conductivity compared to the proton exchange membranes. The ionic conductivity of AEMs can be effectively improved by regulating the microphase structure, but it still cannot meet the practical use requirements. Here, enhanced microphase-separated structures are constructed by the cooperativity of highly hydrophilic dual cations and highly hydrophobic fluorinated side chains. Meanwhile, the introduction of  O enhances the flexibility of side chains and facilitates the formation of ion transport channels. The dual piperidinium cation functionalized membrane (PB2Pip-5C8F) which is grafted with the ultra-hydrophobic fluorocarbon chain exhibits a high conductivity of 74.4 mS cm⁻¹ at 30 °C and 168.46 mS cm⁻¹ at 80 °C. Furthermore, the PB2Pip-5C8F membrane achieves the highest peak power density of 718 mW cm⁻² at 80 °C under a current density of 1197 mA cm⁻² without back pressure. A long-term life cell test of this AEM shows a low voltage decay rate of 1.68 mV h⁻¹ over 70 h of operation at 80 °C.     

Dichlorinated Dithienylethene-Based Copolymers for Air-Stable n-Type Conductivity and Thermoelectricity

Two donor–acceptor (D–A) polymers are obtained by coupling difluoro- and dichloro-substituted forms of the electron-deficient unit BDOPV and the relatively weak donor moiety dichlorodithienylethene (ClTVT). The conductivity and power factors of doped devices are different for the chlorinated and fluorinated BDOPV polymers. A high electron conductivity of 38.3 and 16.1 S cm⁻¹ are obtained from the chlorinated and fluorinated polymers with N-DMBI, respectively, and 12.4 and 2.4 S cm⁻¹ are obtained from the chlorinated and fluorinated polymers with CoCp₂, respectively, from drop-cast devices. The corresponding power factors are 22.7, 7.6, 39.5, and 8.0  µ W m⁻¹ K⁻², respectively. Doping of PClClTVT with N-DMBI results in excellent air stability; the electron conductivity of devices with 50 mol% N-DMBI as dopant remained up to 4.9 S m⁻¹ after 222 days in the air, the longest for an n-doped polymer stored in air, with a thermoelectric power factor of 9.3  µ W m⁻¹ K⁻². However, the conductivity of PFClTVT-based devices can hardly be measured after 103 days. These observations are consistent with morphologies determined by grazing incidence wide angle X-ray scattering and atomic force microscopy.     

Low-Temperature Pulsed-PECVD ZnO Thin-Film Transistors

We report high-quality ZnO thin films deposited at low temperature (200°C) by pulsed plasma-enhanced chemical vapor deposition (pulsed PECVD). Process byproducts are purged by weak oxidants N₂O or CO₂ to minimize parasitic CVD deposition, resulting in high-refractive-index thin films. Pulsed-PECVD-deposited ZnO thin-film transistors were fabricated on plasma-enhanced atomic layer deposition (PEALD) Al₂O₃ dielectric and have a field-effect mobility of 15 cm²/V s, subthreshold slope of 370 mV/dec, threshold voltage of 6.6 V, and current on/off ratio of 10⁸. Thin-film transistors (TFTs) on thermal SiO₂ dielectric have a field-effect mobility of 7.5 cm²/V s and threshold voltage of 14 V. For these devices, performance may be limited by the interface between the ZnO and the dielectric.     

Superior Rate Mesoporous Carbon Sphere Array Composite via Intercalation and Conversion Coupling Mechanisms for Potassium-Ion Capacitors

Carbonaceous materials have been usually adopted as the anode for high energy density potassium-ion hybrid capacitors (KICs) owing to their low voltage plateau, high conductivity, and excellent electrochemical compatibility. The improvements of their specific capacity and sluggish intercalation mechanism are still challenges to further boost the energy density of KICs while maintaining high power density and long cycle life. Herein, a N-doped mesoporous carbon sphere array composite is developed by a dual-templates method. The N-doped carbon sphere array with interpenetrated macro- and meso-pores facilitates the fast electron transport and rapid K⁺ diffusion. The uniformly introduced Co₃O₄ nanoparticles (NPs) confined in the array enable a kinetically boosted conversion reaction for excess and fast K⁺ storage. The partially oxidized Co NPs can efficiently enhance the conductivity of the entire composite. By introducing this optimized conversion capacity from encapsulated Co₃O₄ NPs, the composite with intercalation and conversion coupling mechanisms displays superior capacity and cycle life. The assembled KICs exhibit high energy/power densities (148 Wh kg⁻¹/124 W kg⁻¹) and great cycling performance (94% after 5000 cycles, 0.5 A g⁻¹). This promising strategy demonstrates an example for carbonaceous composite anode with synergistic K⁺ storage hybrid mechanism toward high performance KICs.     

Interface effect in pentacene field-effect transistors from high energy proton beam irradiation

We report the effect of irradiation using 10 MeV high energy proton beams on pentacene organic field-effect transistors (OFETs). The electrical characteristics of the pentacene OFETs were measured before and after proton beam irradiation with fluence (dose) conditions of 10¹², 10¹³, and 10¹⁴ cm⁻². After proton beam irradiation with fluences of 10¹² or 10¹³ cm⁻², the threshold voltage of the OFET devices shifted to the positive gate voltage direction with an increase in the current level and mobility. In contrast, for a high proton beam fluence condition of 10¹⁴ cm⁻², the threshold voltage shifted to the negative gate voltage direction with a decrease in the current level and mobility. It is evident from the electrical characteristics of the pentacene OFETs treated with a self-assembled monolayer that these experimental observations can be attributed to the trapped charges in the dielectric layer and pentacene/SiO₂ interface. Our study will enhance the understanding of the influence of high energy particles on organic field-effect transistors.     

Analysis of the Annealing Budget of Metal Oxide Thin-Film Transistors Prepared by an Aqueous Blade-Coating Process

Metal oxide (MO) semiconductors are widely used in electronic devices due to their high optical transmittance and promising electrical performance. This work describes the advancement toward an eco-friendly, streamlined method for preparing thin-film transistors (TFTs) via a pure water-solution blade-coating process with focus on a low thermal budget. Low temperature and rapid annealing of triple-coated indium oxide thin-film transistors (3C-TFTs) and indium oxide/zinc oxide/indium oxide thin-film transistors (IZI-TFTs) on a 300 nm SiO₂ gate dielectric at 300 °C for only 60 s yields devices with an average field effect mobility of 10.7 and 13.8 cm² V⁻¹ s⁻¹, respectively. The devices show an excellent on/off ratio (>10⁶), and a threshold voltage close to 0 V when measured in air. Flexible MO-TFTs on polyimide substrates with AlO_x dielectrics fabricated by rapid annealing treatment can achieve a remarkable mobility of over 10 cm² V⁻¹ s⁻¹ at low operating voltage. When using a longer post-coating annealing period of 20 min, high-performance 3C-TFTs (over 18 cm² V⁻¹ s⁻¹) and IZI-TFTs (over 38 cm² V⁻¹ s⁻¹) using MO semiconductor layers annealed at 300 °C are achieved.     

Charge trapping in ultrathin Gd2O3 high-k dielectric

Charge trapping in ultrathin high-k Gd₂O₃ dielectric leading to appearance of hysteresis in C-V curves is studied by capacitance-voltage and current-voltage techniques. It was shown that the large leakage current at a negative gate voltage causes the generation of the positive charge in the dielectric layer, resulting in the respective shift of the C-V curve. The capture cross-section of the hole traps is around 2 × 10⁻²⁰ cm². The distribution of the interface states was measured by conductance technique showing the concentration up to 7.5 × 10¹² eV⁻¹ cm⁻² near the valence band edge.     

Superior Thermoelectric Performance of Textured Ca3Co4−xO9+δ Ceramic Nanoribbons

Calcium cobaltite Ca₃Co_4−xO_9+δ (CCO) is a promising p-type thermoelectric (TE) material for high-temperature applications in air. The grains of the material exhibit strong anisotropic properties, making texturing and nanostructuring mostly favored to improve thermoelectric performance. On the one hand multitude of interfaces are needed within the bulk material to create reflecting surfaces that can lower the thermal conductivity. On the other hand, low residual porosity is needed to improve the contact between grains and raise the electrical conductivity. In this study, CCO fibers with 100% flat cross sections in a stacked, compact form are electrospun. Then the grains within the nanoribbons in the plane of the fibers are grown. Finally, the nanoribbons are electrospun into a textured ceramic that features simultaneously a high electrical conductivity of 177 S cm⁻¹ and an immensely enhanced Seebeck coefficient of 200 µV K⁻¹ at 1073 K are assembled. The power factor of 4.68 µW cm⁻¹ K⁻² at 1073 K in air surpasses all previous CCO TE performances of nanofiber ceramics by a factor of two. Given the relatively high power factor combined with low thermal conductivity, a relatively large figure-of-merit of 0.3 at 873 K in the air for the textured nanoribbon ceramic is obtained.     

Record High Power Factor and Low Thermal Conductivity in Amorphous/PbTe/Amorphous Multiple Quantum Wells

Quantum well (QW) superlattice is one of the proposals to improve the thermoelectric properties and provide a rich platform for the next generation of thermoelectric device. Previous QW have two main challenges that need to be addressed: i) decrease the electron tunneling across the layers in the semiconductor-based multiple QWs (MQW), and ii) decrease the thermal conductivity in the oxide-based MQW. Herein, the study demonstrates amorphous based PbTe/amorphous-STO MQWs with ultrahigh power factor of 40.9 µW cm⁻¹ K⁻² and record low thermal conductivity of ≈0.49 W m⁻¹ K⁻¹ at room temperature. The high performance of PbTe/amorphous-STO MQWs is attributed to strong quantum confine effect and its intrinsic low thermal conductivity of amorphous superlattice structure. The results open up a new avenue toward modulating thermoelectric properties beyond traditional MQWs of thermoelectric materials.     

Flexible Liquid-Based Continuous Direct-Current Tribovoltaic Generators Enable Self-Powered Multi-Modal Sensing

Flexible tribovoltaic direct-current (DC) generators are urgently expected by wearable applications. Traditional rigid contact-separation type tribovoltaic DC generators normally have non-ignorable friction loss and cannot sustain outstanding outputs. This hinders their serviceability in continuous motion scenarios. Here, flexible liquid-based DC generators (FLGs) with metal-liquid-semiconductor indium gallium zinc oxide (IGZO) stack structures are reported. The FLG with Pt/H₂O/IGZO structure delivers a peak short-circuit current density up to 2.3 µA cm⁻², a peak open-circuit voltage up to 620 mV, and a power density up to 0.1 µW cm⁻². The differences in the properties of different liquid–solid interfaces are studied by density functional theory, showing that the bond formation, charge-transfer-induced dipole electric field at the solid-liquid interface, and the built-in electric field are responsible for the generation and separation of electron-hole pairs to form continuous DC. The proposed FLG can keep excellent performance even after >5 × 10⁴ shaking cycles or exposing to ambient conditions for 30 days, showing extraordinary stability. Besides charging capacitors or driving LEDs, the FLG is further demonstrated to work for self-powered multifunctional sensing, enabling pressure, position-posture, or temperature detections. This design offers potential solutions and novel possibilities for next-generation self-powered wearable electronics.     

Structural and frequency-dependent dielectric properties of PVP-SiO2-TMSPM hybrid thin films

In the present study, thin films of PVP-SiO₂-TMSPM (polyvinylpyrrolidone-silicon dioxide- 3-trimethoxysilyl propyl metacrylate) were deposited on p-type Si (111) substrates using spin coating technique. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDS) were applied to investigate the chemical bonds and structural properties of the samples. Morphology of the hybrid thin films was studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. The frequency dependence of dielectric properties such as dielectric constant (ε^′), dielectric loss (ε″), loss tangent (tan δ) as well as the real component of electric modulus (M′), imaginary component of electric modulus (M″), and AC electrical conductivity (σ_AC) was studied in Al/PVP-SiO₂-TMSPM/PSi used as a metal-polymer-semiconductor (MPS) device. Analysis of dielectric relaxation behavior was performed in the frequency range of 0.1 KHz to 1 MHz. In the frequency range of 1 KHz to 1 MHz, the σ_AC data were varied from 6.35 × 10⁻⁶ to 9.02 × 10⁻⁶ for the sample with 0.15 wt ratios of TMSPM and equivalent values of both PVP and SiO₂. The dielectric, modulus, and AC conductivity analyses were considered the useful factors to detect the effects of the capacitance, ionic conductivity, and dielectric relaxation process.     

A facile chemical reduction approach for effectively tuning thermoelectric properties of PEDOT films

Poly(3,4-ethylenedioxythiophene)–tosylate–polyethylene glycol–polypropylene glycol–polyethylene glycol (PEDOT–Tos–PPP) films were prepared via a vapor phase polymerization (VPP) method. The films possess good electrical conductivity (1550 S cm⁻¹), low Seebeck coefficient (14.9 μV K⁻¹) and thermal conductivity (0.501 W m⁻¹ K⁻¹), and ZT ∼ 0.02 at room temperature (RT, 295 K). Then, the films were treated with NaBH₄/DMSO solutions of different NaBH₄ concentrations to adjust the redox level. After the NaBH₄/DMSO treatment (dedoping), the electrical conductivity of the films continuously decreased from 1550 to 5.7 S cm⁻¹, whereas the Seebeck coefficient steeply increased from 14.9 to 143.5 μV K⁻¹. A maximum power factor of 98.1 μW m⁻¹ K⁻² has been achieved at an optimum redox level. In addition, the thermal conductivity of the PEDOT–Tos–PPP films decrease from 0.501 to 0.451 W m⁻¹ K⁻¹ after treated with 0.04% NaBH₄/DMSO solution. A maximum ZT value of 0.064 has been achieved at RT. The electrical conductivity and thermal conductivity (Seebeck coefficient) of the untreated and 0.04% NaBH₄/DMSO treated PEDOT–Tos–PPP films decrease (increases) with increasing temperature from 295 to 385 K. And the power factor of the films monotonically increases with temperature. The ZT at 385 K of the 0.04% NaBH₄/DMSO treated film is 0.155.     

Rational Engineering CoxOy Nanosheets via Phosphorous and Sulfur Dual-Coupling for Enhancing Water Splitting and Zn–Air Battery

Herein, an efficient multifunctional catalyst based on phosphorus and sulfur dual-doped cobalt oxide nanosheets supported by Cu@CuS nanowires is developed for water splitting and Zn–air batteries. The formation of such a unique heterostructure not only enhances the number and type of electroactive sites, but also leads to modulated electronic structure, which produces reasonable adsorption energy toward the reactant, thereby improving electrocatalytic efficiency. The catalyst demonstrates small overpotentials of 116 and 280 mA cm⁻² to achieve 10 mA cm⁻² for hydrogen and oxygen evolution, respectively. As a result, a developed electrolyzer displays a cell voltage of 1.52 V at 10 mA cm⁻² and long-term stability with a current response of 92.3% after operating for 30 h. Moreover, using such a catalyst in the fabrication of a Zn–air battery also leads to a cell voltage of 1.383 V, along with a power density of 130 mW cm⁻² at 220 mA cm⁻².     

The role of water in the device performance of n-type PTCDI-C8 organic field-effect transistors with solution-based gelatin dielectric

Gelatin is a natural protein, which works well as the gate dielectric for N,N-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C₈) organic field-effect transistors (OFETs). An aqueous solution process was applied to form the gelatin gate dielectric on poly(ethylene terephthalate) (PET) by spin-coating and subsequent casting. The field-effect mobility in the saturation regime (μ_FE,sat) and the threshold voltage (V_T) values of a typical 40 nm PTCDI-C₈ OFET are (0.22 cm² V⁻¹ s⁻¹, 55 V) in vacuum and (0.74 cm² V⁻¹ s⁻¹, 2.6 V) in air ambient. The maximum voltage shift in hysteresis is also reduced from 10 V to 2 V when the operation environment for PTCDI-C₈ OFETs is changed from vacuum to air ambient. Nevertheless, a slight reduction of electron mobility was found when the device was stressed in the air ambient. The change in the device performance has been attributed to the charged ions generation owing to water absorption in gelatin in air ambient.     

Dielectric surface-polarity tuning and enhanced operation stability of solution-processed organic field-effect transistors

The electrical performance of triethylsilylethynyl anthradithiophene (TES-ADT) organic field-effect transistors (OFETs) was significantly affected by dielectric surface polarity controlled by grafting hexamethyldisilazane and dimethyl chlorosilane-terminated polystyrene (PS-Si(CH₃)₂Cl) to 300-nm-thick SiO₂ dielectrics. On the untreated and treated SiO₂ dielectrics, solvent–vapor annealed TES-ADT films contained millimeter-sized crystals with low grain boundaries (GBs). The operation and bias stability of OFETs containing similar crystalline structures of TES-ADT could be significantly increased with a decrease in dielectric surface polarity. Among dielectrics with similar capacitances (10.5–11 nF cm⁻²) and surface roughnesses (0.40–0.44 nm), the TES-ADT/PS-grafted dielectric interface contained the fewest trap sites and therefore the OFET produced using it had low-voltage operation and a charge-carrier mobility ∼1.32 cm² V⁻¹ s⁻¹, on–off current ratio >10⁶, threshold voltage ∼0 V, and long-term operation stability under negative bias stress.     

Dielectric Modulated Glass Fiber Fabric-Based Single Electrode Triboelectric Nanogenerator for Efficient Biomechanical Energy Harvesting

Single-electrode triboelectric nanogenerators (SE-TENGs) are versatile tools for energy harvesting with simple structures and great practicability. However, low output performance hinders SE-TENGs in applications as portable power sources. Herein, a novel SE-TENG that utilizes glass fiber fabric (GFF) as tribo-materials, along with an inorganic ferroelectric film for the dielectric layer is proposed. The GFF is first shown to be a promising tribo-material for its highly positive tribo-polarity and unique chemical/mechanical/durable properties. Meanwhile, an inorganic dielectric film with high dielectric constant is introduced between the GFF and Al electrode for enhancing the charge trapping capability. Owing to the synergistic effect of optimized triboelectrification and dielectric properties, the specific designed SE-TENG delivers an open-circuit voltage of 1640 V and a short-circuit current density of 59.05 mA m⁻², which are superior to most reported SE-TENGs. With a maximum instantaneous power of 11.30 mW, the device can light up 1350 light-emitting diodes, charge a 47 µF capacitor into 10 V in 421 s, and power up a digital watch even without additional control circuits. This work provides new insights in designing high-performance SE-TENGs and facilitates their application in biomechanical energy harvesting and portable power sources.     

Tailoring Anion Association Strength Through Polycation-Anion Coordination Mechanism in Imidazole Polymeric Ionic Liquid-Based Artificial Interphase toward Durable Zn Metal Anodes

Artificial interface layer engineering is an efficacious modification strategy for protecting zinc anode from dendrite growth and byproducts formation. However, the high bulk ionic conductivity of most artificial interfacial layers is mainly contributed by the movement of anions (SO₄²⁻), which is the source of parasitic reactions on zinc anode. Herein, a high zinc ion donor transition (σZn²⁺ = 3.89 × 10⁻² S cm⁻¹) imidazole polymeric ionic liquid interface layer (1-carboxymethyl-3-vinylimidazolium bromide monomer, CVBr) for Zn metal protection is designed. The N⁺ atom of imidazole rings is connected by chains to form the cavities and the anions are confined within these cavities. Thus, the hindering effect of surrounding units on the anions leads to the subdiffusive regime, which inhibits the diffusion of SO₄²⁻ in interface and increases Zn²⁺ transference number. Besides, the polycation-anion coordination mechanism of PolyCVBr ensures accelerated Zn²⁺ transition and realizes rapid internal Zn²⁺ migration channel. As a result, the Zn@CVBr||AM symmetry cells deliver high bulk ionic conductivity (4.42 × 10⁻² S cm⁻¹) and high Zn²⁺ transference number (tZn²⁺ = 0.88) simultaneously. The Zn@CVBr||AM-NaV₃O₈ pouch cells display the capacity retention of 88.9% after 190 cycles under 90° bending, verifying their potential practical application.     

A new concept for test equipment for testing large HV and UHV cables on-site

The number of projects involving long and extra long HV and UHV AC cables as well as HVDC cable connections can be observed to increase (Cao et al., 2008; Kabouris et al., 2006). At the same time, operating voltage levels are increasing, accentuating the need for more powerful on-site test systems needed to prove the integrity of the insulation before energization. Low cost and ease of operation are other important features of such systems. As a matter of fact, traditional methods and test systems for routine and on-site testing of these cables come to their limit – technically and economically – as the lengths and voltage levels increase (Marelli, 2008). The logistics for the arrangement of tests as well as the testing itself are challenging (Schr?der et al., 2006). Development of power electronics has now made it possible to realize high voltage DC interconnections that do not exhibit polarity reversal at reversal of power flow. As a result of this, extruded XLPE cables are now coming to the fore in high voltage DC application, although methods and test equipment for routine and on-site testing show some open issues so far. Space charges in the insulation, initiated by the test voltage during testing, are unacceptable, and this leads to the requirement that testing must be made at an alternating voltage, which can be very low frequency without creating space charge. Available test equipment for power frequency testing is not feasible for testing extruded DC cables, among other reasons, due to the lengths usually associated with DC cables. These open issues can be solved with a newly developed on-site test system that provides the reliability of established test methods and test equipment, but exhibiting lower weight, dimensions and power consumption compared to existing systems. At the same time, the on-site test system as well as the prearrangement of the tests and the testing itself are less cost intensive. Extra long cables (i.e. high capacitance) could be tested with the equipment, which by virtue of its smaller dimension is easier to handle and thus reducing the testing logistics dramatically. For example where one of the systems on the market would require two trailers of equipment for a test on a high voltage cable, only a single trailer would be needed with the new system, or a roll on/roll off test can be carried out without the use of any crane on-site. A reduction in weight by a factor of 3 is expected compared to today’s on-site test equipment, a gain which also is reflected in reduced volume.