High Electrical Performance Research Articles

Graphene/polyamide-6 microsphere composites with high electrical and mechanical performance

The development of innovative methods to prepare graphene-based polymer composites with remarkable properties has become a priority due to the many practical applications of these microstructures. Herein, a new technology was used to fabricate composites by combining graphene materials and polymer microspheres. Polyamide 6 (PA6) microspheres were synthesised by reaction-induced phase separation method, and they were wrapped with few-layer graphene (FLG) or graphene oxide (GO) by exfoliated adsorption method, which allows FLG and GO sheets to form a three-dimensional network structure in the PA6 matrix. Electrical and mechanical characterisation led to a distinct improvement in the properties of PA6 composites, which were superior to traditional graphene/polymer composites. Moreover, the process proposed in this work proved to be an effective method to prepare graphene/polymer composites, suitable for industrial production, and can be extended to other kinds of composites with nanofillers.

Freestanding Multi-Gate Amorphous Oxide-Based TFTs on Graphene Oxide Enhanced Electrolyte Membranes

Freestanding thin-film transistors (TFTs) with multiple in-plane gates could meet increasing demands of mechanical flexibility and multifunctional integration. In this letter, freestanding flexible indium-zinc-oxide based TFTs with multi-gate structure and high electrical performance were reported. No obviously electrical degradation is observed under various mechanical stimuli due to the mechanical reinforcement effect of graphene oxide. Multifunctional operations including AND, OR gates and a Schmitt trigger are successfully demonstrated. More importantly, OR logic to AND logic transformation is also realized by a third modulatory terminal. Such freestanding TFTs are promising candidates for next-generation flexible smart electronic systems.

Optimization of Titanium Dioxide Nanoparticles in Mesoporous Electron Transport Layer Perovskite Solar Cell

Research about mesoporous TiO2 as an electron transport layer in perovskite solar cell has been done to obtain the best fabricated cell’s performance. In this research, the concentrations of opaque and transparent TiO2 nanoparticle were varied, in order to optimize the TiO2 mesoporous electron transport layer in FTO/CL-TiO2/MS-TiO2/Perovskite/P3HT/Ag perovskite-based solar cell. Morphological, optical, and electrical characteristics of TiO2 layers were investigated using scanning electron microscopy (SEM), four-point probe (FPP), and UV-Vis spectroscopy. The influences of those characteristics in solar cell performance were analyzed by using illumination of sun simulator with a light intensity of 500 W/m2. The results showed that transparent TiO2 has a higher conductivity and transmittance compared to the opaque TiO2. The concentration of TiO2 solutionin1:17 ratio resulted in higher electrical performance in both the transparent and opaque TiO2 layer. The best perovskite solar cell performance with PCE of 0.37% was achieved from the sample using TiO2 transparent layer with a concentration of 1:7 ratio.

Enhanced temperature stability in high piezoelectric performance of (K, Na)NbO3-based lead-free ceramics trough co-doped antimony and tantalum

Although KNN-based ceramics with high electric performance have been obtained by phase engineering strategy, the temperature stability is required to be the improved in the applications. Herein, a new environment-friendly 0.96K0·4Na0·6Nb0.97-xTa0.03SbxO3-0.04(Bi0.45Sm0.05)Na0·5ZrO3 (KNNTSx-BSNZ, x = 0–0.08) ceramic system was designed, which exhibits excellent piezoelectric properties and good temperature stability. A high piezoelectric property of 510 pC/N is obtained by R-T phase engineering in the ceramics with x = 0.045. The temperature stability of electric properties is improved in the temperature range of T = 20–180 °C by Ta, Sb co-doping in KNNTSx-BSNZ ceramics with x = 0.02–0.045, benefiting from the combined effects of both the enhanced relaxor behavior and high TC. Therefore, we believe that it can broaden the application of KNN-based ceramics.

Deformation‐induced stress/strain mapping and performance evaluation of a‐IGZO thin‐film transistors for flexible electronic applications

AbstractIn the flexible electronics sector, there is an urgent need for higher performance, and hence, many new technologies are emerging in recent years. The field of organic and printed electronics allows low production costs and large areas. The silicon technology allows nanometric resolutions and better performance. A new technology CAD (TCAD)‐based design methodology is needed to combine both mechanical flexibility and high performance. This work presents a predictive TCAD calibration methodology for indium‐gallium‐zinc‐oxide thin‐film transistors (TFTs), employing physics‐based modeling to support and enhance simulation‐based device development. In this work, based on the nonlinear finite element technique, a TCAD framework has been developed to introduce different types of large deformations and obtain the local stress/strain profiles (mapping) inside the devices. The impacts of various kinds of deformations on the electrical characteristics of the strained TFTs are studied. The feasibility (via predictions) for amorphous‐indium‐gallium‐zinc‐oxide (a‐IGZO) TFTs, combining considerable mechanical flexibility, high electrical performance, and finally, excellent stability under deformation, may be useful for mechanical deformation‐aware design and modeling for highly flexible electronics. To the best of our knowledge, the highest cutoff frequency (fT > 690 MHz) possible for strain‐engineered a‐IGZO TFTs is predicted in entirely flexible technologies that can be used to realize active transceivers operating in the MHz regime.

The Critical Role of Dopant Cations in Electrical Conductivity and Thermoelectric Performance of n-Doped Polymers.

The low n-doping efficiency of conjugated polymers with the molecular dopants limits their availability in electrical conductivity, thermoelectrics, and other electric applications. Recently, considerable efforts have focused on improving the ionization of dopants by modifying the structures of host polymers or n-dopants; however, the effect of ionized dopants on the electrical conductivity and thermoelectric performance of the polymers is still a puzzle. Herein, we try to reveal the role of molecular dopant cations on carrier transport through the systematic comparison of two n-dopants, TAM and N-DMBI-H. These two n-dopants exhibit various doping features with the polymer due to their different chemical structure characteristics. For instance, while doping, TAM negligibly perturbs the polymer backbone conformation and microstructural ordering; then after ionization, TAM cations possess weak π-backbone affinity but strong intrinsic affinity with side chains, which enables the doped system to screen the Coulomb potential spatially. Such doping features lead to high carrierization capabilities for TAM-doped polymers and further result in an excellent conductivity of up to 22 ± 2.5 S cm-1 and a power factor of over 80 μW m-1 K-2, which are significantly higher than the state of the art values of the common n-dopant N-DMBI-H. More importantly, this strategy has also proven to be widely applicable in other doped polymers. Our investigations indicate the vital role of dopant counterions in high electrical and thermoelectric performance polymers and also suggest that, without sacrificing Seebeck coefficients, high conductivities can be realized with precise regulation of the interaction between the cations and the host.

B 12/ CNT anodic nano catalysis applied on polishing the performance of microbial fuel cells

Microbial fuel cells (MFCs) are a newly emerging technology in bioenergy processing. This research is to replace the use of platinum catalysts. Three types of oxygen reduction catalysts (B12/XC-72, B12/CNT and B12/AC) are analyzed and compared with the other two activated sludge and no catalyst where the performance of activated carbon in MFCs are evaluated. The results show that the catalyst with B12 vitamin as the main body has a higher open-circuit voltage. Among them, the open-circuit voltage of B12/CNT is the highest with 0.667 V, which is about 2 times that of MFCs without catalyst. The highest electrical performance with 0.54 W m−2 is 3.17 times that of catalyst-free MFCs, which shows that the self-made B12/CNT catalyst MFCs have the best performance in this study. The related research will be helpful for the application of wastewater to energy.

Mechanochemical processing of BaZr1−yYyO3−δ (y = 0.15, 0.20) protonic ceramic electrolytes: Phase purity, microstructure, electrical properties and comparison with other preparation routes

BaZrO3-based materials have been intensively researched due to their potential application as high-temperature proton conductors in devices such as proton ceramic fuel cells (PCFCs), separation membranes and electrolysers. Nonetheless, their implementation in these devices has often been constrained due to their processing difficulties, namely the formation of Ba-deficient compositions, coexistence of separate perovskite phases or the formation of segregated phases of the acceptor dopant. In this context, the current article shows mechanosynthesis to be an efficient preparation method for Ba(Zr,Y)O3-δ materials, producing pure powders, containing nanometric crystallites, that offer good densification and grain growth. The phase formation, microstructure and electrical properties of the most promising BaZr1-yYyO3-δ compositions, with yttrium contents of y = 0.15 (BZY15) and y = 0.20 (BZY20) are investigated and compared with literature data of materials made by other processing routes. Such a comparison highlights that phase separation of such compositions, commonly reported in the literature, does not occur for these mechanosynthesised materials of high homogeneity. Furthermore, high electrical performances can be obtained by this technique that can compete with some of the best reported in the literature. Electrical conductivity as a function of both oxygen and water partial pressure, in the temperature range of 550 °C − 850 °C, are measured for both compositions and the partial conductivities of protons, oxygen vacancies and electron holes are determined from the defect model. The electron-hole conductivity of BZY20 is observed to be higher than that of BZY15 under all conditions, while proton and oxide-ion conductivities are shown to be higher for the composition BZY15.

A promising strategy for efficient electromagnetic interference shielding by designing a porous double-percolated structure in MWCNT/polymer-based composites

Porous conductive polymer composites (CPCs) are supposed to be the most prospective substitutes for metal-based materials in the field of electromagnetic interference (EMI) shielding but are still confronted with the challenge of poor performance. To solve the dilemma, we firstly design a porous double-percolated structure in co-continuous polystyrene (PS)/polymethyl methacrylate (PMMA)/ MWCNT system with a judicious combination of melt blending and supercritical carbon dioxide (scCO2) foaming. At thickness of 2 mm and MWCNT content of 1.61 vol%, the porous composite possessed low-density (0.4 g/cm3), high electrical conductivity (1.64 S/m) and efficient EMI shielding performance (23.08 dB). Moreover, the percolation threshold decreased from 0.18 to 0.14 vol%, and the specific EMI SE increased from 37.79 to 57.7 dB·cm3/g compared to the solid counterparts. This work offers a novel idea for the design of lightweight EMI shielding materials with high performance, exerting tremendous potential in electronics and aerospace fields.

Stimuli-responsive polymer as gate dielectric for organic transistor sensors

Abstract Temperature is a characteristic often correlated with environmental and health issues. This paper presents an organic thin film transistor (OTFT) based temperature sensor having a detection range of 30–45 °C, which, therefore, encompasses the human body temperature. The OTFT sensor featured thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and pentacene as the gate dielectric and semiconductor, respectively. The PNIPAM film possessed a dielectric constant of 4.2 with very low leakage current density. The OTFT exhibited high electrical performance, with a hole mobility (μ) of 0.90 ± 0.04 cm2 V−1 s−1, a threshold voltage (Vth) of −15.4 ± 1.16 V, and an on/off ratio of 104. Significant changes in the drain current and the values of Vth and μ occurred when the temperature of the device was varied within the range 30–45 °C at an interval of 0.5 °C. The operating principle for this temperature sensor was based on the structural transformation of the PNIPAM dielectric and the enhanced charge transport of the pentacene semiconductor upon varying the temperature. Flexible OTFTs fabricated on polyethylene terephthalate substrate displayed hole mobilities as high as 0.39 ± 0.01 cm2 V−1 s−1, values of Vth of −18.6 ± 0.45, and on/off ratios of 102, and were workable for over 100 bending cycles.

Cellulose II Aerogel-Based Triboelectric Nanogenerator.

Cellulose-based triboelectric nanogenerators (TENGs) have gained increasing attention. In this study, a novel method is demonstrated to synthesize cellulose-based aerogels and such aerogels are used to fabricate TENGs that can serve as mechanical energy harvesters and self-powered sensors. The cellulose II aerogel is fabricated via a dissolution-regeneration process in a green inorganic molten salt hydrate solvent (lithium bromide trihydrate), where. The as-fabricated cellulose II aerogel exhibits an interconnected open-pore 3D network structure, higher degree of flexibility, high porosity, and a high surface area of 221.3 m2 g-1. Given its architectural merits, the cellulose II aerogel-based TENG presents an excellent mechanical response sensitivity and high electrical output performance. By blending with other natural polysaccharides, i.e., chitosan and alginic acid, electron-donating and electron-withdrawing groups are introduced into the composite cellulose II aerogels, which significantly improves the triboelectric performance of the TENG. The cellulose II aerogel-based TENG is demonstrated to light up light-emitting diodes, charge commercial capacitors, power a calculator, and monitor human motions. This study demonstrates the facile fabrication of cellulose II aerogel and its application in TENG, which leads to a high-performance and eco-friendly energy harvesting and self-powered system.

Rigorous Study on Hump Phenomena in Surrounding Channel Nanowire (SCNW) Tunnel Field-Effect Transistor (TFET)

In this paper, analysis and optimization of surrounding channel nanowire (SCNW) tunnel field-effect transistor (TFET) has been discussed with the help of technology computer-aided design (TCAD) simulation. The SCNW TFET features an ultra-thin tunnel layer at source sidewall and shows a high on-current (ION). In spite of the high electrical performance, the SCNW TFET suffers from hump effect which deteriorates subthreshold swing (S). In order to solve the issue, an origin of hump effect is analyzed firstly. Based on the simulation, the transfer curve in SCNW TFET is decoupled into vertical- and lateral-BTBTs. In addition, the lateral-BTBT causes the hump effect due to low turn-on voltage (VON) and low ION. Therefore, the device design parameter is optimized to suppress the hump effect by adjusting thickness of the ultra-thin tunnel layer. Finally, we compared the electrical properties of the planar, nanowire and SCNW TFET. As a result, the optimized SCNW TFET shows better electrical performance compared with other TFETs.

Highly flexible, porous electroactive biocomposite as attractive tribopositive material for advancing high-performance triboelectric nanogenerator

The triboelectric property of the tribomaterials is essential for high-performance triboelectric nanogenerators (TENGs). Currently, the available tribopositive material is still limited and there is a strong need to explore attractive tribomaterials with high positive tribopolarity, biocompatibility, and easy preparation. Herein, we proposed porous cellulose acetate (CA)-polyethyleneimine (PEI) biocomposite (CP biocomposite) and employed it as an effective tribopositive material, paired with flexible low-temperature vulcanized silicone rubber (LTV) tribonegative membrane, to develop high-output CP/LTV-TENG. The mass ratio of CA/PEI and thickness of CP biocomposite were optimized systematically, and the CP biocomposite with CA/PEI mass ratio of 3:1 and the thickness of 55 μm is recognized as an optimal sample. The corresponding CP/LTV-TENG could deliver the open-circuit voltage (V OC ) of 478 V, short-circuit current density (J SC ) of 6.3 μA/cm 2 , and power density of 2.21 mW/cm 2 under the applied force of 16 N and frequency of 1.5 Hz, much higher than that of CA membrane-based CA/LTV-TENG. Further, the mechanism for the improved working performance of CP/LTV-TENG was discussed, and it revealed that the synergistic effect of surface electron-donating ability and inner porous structure of CP biocomposite is mainly responsible for the high electrical performance. Additionally, the CP/LTV-TENG presented outstanding electrical output stability and durability, and it is effectively capable of powering electronics and performing movement detection. This work confirms the feasibility of the proposed CP biocomposite as effective tribopositive material for developing high-power TENGs and offers insights for designing novel bio-tribomaterial in the advancement of eco-friendly TENGs. • A flexible, porous electroactive CP biocomposite is proposed as a tribopositive material for developing high-output TENGs. • CP biocomposite is optimized by exploring the effect of CA/PEI mass ratio and the thickness on the electrical performance. • Synergistic effect of surface tribopolarity and inner porosity of CP biocomposite is responsible for the enhanced outputs. • The CP/LTV-TENG is efficiently capable of powering microelectronics and performing body motion detection.

Novel chemically cross-linked chitosan-cellulose based ionogel with self-healability, high ionic conductivity, and high thermo-mechanical stability

Developing flexible electrochemical devices with high-performance electrolytes by using natural renewable polymer is of great significance for meeting green and sustainable energy requirements. Here, a new type of chemically cross-linked ionogel based on natural chitosan and cellulose with good self-healability has been designed by a two-step method in ionic liquid. The rheological and dynamic mechanical analysis tests revealed that the as-prepared ionogel exhibited excellent thermo-mechanical stability even when the temperature was as high as 150 °C. Furthermore, the obtained ionogels showed good frost resistance, and still could maintain excellent flexibility even when the temperature was as low as − 20 °C. More importantly, the ionogel showed superior room temperature ionic conductivity (up to 2.1 mS/cm) and retained high electrical performance over a temperature range from − 50 to 120 °C. Additionally, the ionogel was used as electrolyte for preparing flexible supercapacitors and showed good performance under high temperature and harsh mechanical conditions. Such an ionogel, based on natural polymers with robust mechanical properties, high ionic conductivity, self-healability, and wide working temperature range, could be very useful for next-generation sustainable electrochemical devices.

Electrical and mechanical properties of polypropylene/epoxy blend-graphite/carbon black composite for proton exchange membrane fuel cell bipolar plate

Conductive polymer composites (CPCs) exhibit favorable density and corrosion resistance for application as bipolar plate (BP) in proton exchange membrane fuel cell (PEMFC). However, achieving CPCs that combine the required level of electrical conductivity and mechanical strength is a challenge that has limited their application in PEMFC BPs. This study explored the potential of achieving CPC BPs with high electrical and mechanical performance by using carbon black (CB) as a secondary filler in graphite-polymer composites. Polypropylene (PP)/epoxy blend was selected as the matrix due to its good combination of strength and toughness as well as its potential to form a co-continuous morphology, which promotes the formation of more continuous conducting networks within the composite, leading to enhanced electrical performance. The PP/epoxy/graphite/CB composites were prepared by melt mixing in a Rheomixer at 190 °C and 60 rpm for 10 min, followed by compression molding at 200 °C and 6 metric tonnes for 10 min. The electrical conductivity of the composites increased from 49.26 Scm−1 to 90.34 Scm−1 (in-plane) and from 0.37 Scm−1 to 9.34 Scm−1 (through-plane) as the total filler content increased from 50 to 85 wt%. The flexural strength initially increased from 45.57 MPa at 50 wt% to 51.84 MPa at 60 wt% total filler content. Further increase in total filler content led to a decrease in flexural strength. The nanosize CB particles, used as a minor filler, filled the voids between the graphite particles, leading to the formation of more conducting pathways and higher electrical conductivities compared to the PP/epoxy/graphite composites without CB fillers. The PP/epoxy/graphite/CB composite with 80 wt% total filler content exhibited the most promising in-plane conductivity (88.5 Scm−1), through-plane conductivity (8.52 Scm−1), and flexural strength (28.53 MPa) for BP application.

Effect of epoxy mold compound and package dimensions on the thermomechanical properties of a fan-out package

The fan-out wafer level package (FOWLP) is the most common advanced package technology due to its higher I/O density, ultra-thin profile, high electrical performance, and low power consumption. However, warpage induced by the coefficient of thermal expansion (CTE) mismatch between different kinds of materials is a mechanical issue in FOWLPs. We investigated the warpage of fan-out package (FO package) components molded by EMC (with 3 kinds of materials) for two mold thicknesses. The fan-out package component was fabricated with Si chips (three thicknesses). The warpage of the fan-out package component from room temperature to 260 °C decreased with increasing chip thickness and mold thickness. Finite element method (FEM) analysis showed that the warpage of the fan-out package at 25 °C decreased when the CTE mismatch between the EMC and Si chip decreased. The warpage of the fan-out package at 260 °C decreased with decreasing modulus of the EMC due to a lower stress relaxation. The electrical resistance of the FOWLP component increased more than 2.5 times after temperature–humidity and thermal shock testing. The warpage decreased with increasing EMC thickness, decreasing chip thickness, a lower CTE of the EMC, and a lower modulus of the EMC.

Dehydration of Cations Inducing Fast Ion Transfer and High Electrical Capacitance Performance on Graphene Electrode in Aqueous Electrolytes

We fabricated single-layer graphene as an ideal two-dimensional electrode for evaluating fundamental mechanism of ion transfer into a capacitance system and conducted cyclic voltammetry and molecul...

Annual analysis of a multi-functional BIPV/T solar wall system in typical cities of China

Firstly, this paper introduces a novel multi-functional BIPV/T wall system in order to satisfy building’s seasonal energy demand in China. This system can generate electricity during the whole year. In heating season, hot air is created to decrease heating load for the building. In non-heating season, hot water is generated to supply the household demand. Meanwhile temperature of PV panel is decreased by water cycle, therefore higher electrical performance is able to be achieved. Secondly, mathematical model is established and verified by the experimental results. Thirdly, annual performance of the system in three different typical cities are evaluated. The annual electrical generation in Beijing, Hefei and Xining are 247.7 kWh, 152.6 kWh and 268.4 kWh respectively. The solar fraction in Beijing, Hefei and Xining are 49.9%, 38.7% and 41.3% respectively. The system is able to satisfy 79.1%, 66.8% and 60.4% hot water energy demand in these cities respectively. The overall annual energy saving in Beijing, Hefei and Xining are 2661.8 kWh, 1908.4 kWh and 2412.3 kWh respectively. Fourthly, the impact of external/internal PV structures, Si/CdTe solar cells and aspect ratio of the system are investigated respectively.

High-Mobility Flexible Oxyselenide Thin-Film Transistors Prepared by a Solution-Assisted Method.

Two-dimensional (2D) semiconductors hold great promise in flexible electronics because of their intrinsic flexibility and high electrical performance. However, the lack of facile synthetic and subsequent device fabrication approaches of high-mobility 2D semiconducting thin films still hinders their practical applications. Here, we developed a facile, rapid, and scalable solution-assisted method for the synthesis of a high-mobility semiconducting oxyselenide (Bi2O2Se) thin film by the selenization and decomposition of a precursor solution of Bi(NO3)3·5H2O. Simply by changing the rotation speed in spin-coating of the precursor solution, the thicknesses of Bi2O2Se thin films can be precisely controlled down to few atomic layers. The as-synthesized Bi2O2Se thin film exhibited a high Hall mobility of ∼74 cm2 V-1 s-1 at room temperature, which is much superior to other 2D thin-film semiconductors such as transition metal dichalcogenides. Remarkably, flexible top-gated Bi2O2Se transistors showed excellent electrical stability under repeated electrical measurements on flat and bent substrates. Furthermore, Bi2O2Se transistor devices on muscovite substrates can be readily transferred onto flexible polyvinyl chloride (PVC) substrates with the help of thermal release tape. The integration of a high-mobility thin-film semiconductor, excellent stability, and easy transfer onto flexible substrates make Bi2O2Se a competitive candidate for future flexible electronics.

High-Performance and Flexible Neodymium-Doped Indium-Zinc-Oxide Thin-Film Transistor With All Copper Alloy Electrodes

In this paper, we examine the possibility of using homogeneous and monolayer Cu-0.08 wt. % Cr-0.05 wt. % Zr (CuCrZr) ternary alloy film as both bottom-gate and source/drain (S/D) electrodes for flexible neodymium-doped indium-zinc-oxide (NdIZO) thin-film transistor (TFT) applications. Under the optimized sputtering parameters (250 W & 1.4 mtorr) and annealing process (380 °C & text4 h, N2 atmosphere), the resistivity of the alloy film is as low as $2.47~\mu \cdot $ cm (300 nm) and the adhesion strength to polyimide (PI) substrate reaches 4 B-5 B level, which is competent for high-performance flexible display. As a result, the flexible NdIZO-TFTs with all-CuCrZr electrodes operate in enhancement mode with both high electrical performance ( $\mu _{{\text {FE}}}$ of 32.1 cm2/ $\text{V}\cdot \text{s}$ , Ion/Ioff of 107, Vth of 0.42 V, SS of 0.16 V/decade, RC-norm of $84.5\Omega \cdot $ cm and Vth of −0.28 V/+2.46 V under ±1MV/cm positive/negative bias stress (NBS/PBS) for 5400 s) and good mechanical flexible performance (Vth of only −0.32 V/−0.29 V under r-2.5mm-static and 10K-times-dynamic bending test).