Outstanding Electrical Performance Research Articles

Bio-inspired hydrophobic/cancellous/hydrophilic Trimurti PVDF mat-based wearable triboelectric nanogenerator designed by self-assembly of electro-pore-creating

Electrical performances, output stability and use of comfort are three crucial indexes for the rapid advancements in wearable power generators. However, there exist few studies that can simultaneously improve the three aforementioned indexes in a simple manner. Here, a bio-inspired Trimurti poly(vinylidene fluoride) (PVDF) tribo-material with a transcendent electrical performance, excellent output stability in high environmental humidity, and increased use of comfort under a sweating condition is designed, by simple self-assembly of electro-pore-creating. The nanoporous cancellous-bone-like, hydrophobic lotus-leaf-like, and hydrophilic root-xylem-like structures are assembled respectively in the interior, on the upper surface and on the bottom surface of Trimurti PVDF mat, endowing the fabricated Trimurti triboelectric nanogenerator (T-TENG) with outstanding electrical performances and availability in different application environments. With a high power density of 10.6 W m−2, the T-TENG can directly drive 714 light-emitting-diodes and small electronics. Additionally, under the relative humidity of 85%, the output retention rate of the T-TENG reaches up to 22%. Under the simulated sweating condition, the Trimurti PVDF mat can absorb sweat into its bottom region to accelerate evaporation of sweat. This work indicates a substantial progress of wearable high-performance power sources for dealing with various complex conditions in practical applications.

Research Progress on Flexible Oxide-Based Thin Film Transistors

Oxide semiconductors have drawn much attention in recent years due to their outstanding electrical performance, such as relatively high carrier mobility, good uniformity, low process temperature, optical transparency, low cost and especially flexibility. Flexible oxide-based thin film transistors (TFTs) are one of the hottest research topics for next-generation displays, radiofrequency identification (RFID) tags, sensors, and integrated circuits in the wearable field. The carrier transport mechanism of oxide semiconductor materials and typical device configurations of TFTs are firstly described in this invited review. Then, we describe the research progress on flexible oxide-based TFTs, including representative TFTs fabricated on different kinds of flexible substrates, the mechanical stress effect on TFTs and optimized methods to reduce this effect. Finally, an outlook for the future development of oxide-based TFTs is given.

Conductive heterogeneous blend composites of PP/PA12 filled with ionic liquids treated-CNT

Multi-walled carbon nanotube (CNT) was non-covalently functionalized with alkyl phosphonium-ionic liquids bearing phosphinate (IL-TMP) and bistriflimide (IL-TFSI) as the counter-anions in proportions of 1:1 and 1:5 by weight) to obtain black pastes that were incorporated in polypropylene (PP)/polyamide12 (PA12) (80:20 wt. %) blend by melt mixing. All composites were prepared with 1 phr of CNT. The effect of the ILs on the AC electrical conductivity, rheological measurements, thermal properties and dielectric properties of the PP/PA12 composites was evaluated. Also, the morphology of the composites was studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The presence of IL resulted in an increase of the electrical conductivity and the best performance was achieved by using IL-TFSI where a proportion of CNT/IL-TFSI = 1:1 was enough to promote an improvement of this property by three orders of magnitude. This system also presented improved complex viscosity and increased storage modulus, obtained by dynamic-mechanical analysis (DMA). CNT has a tendency to be located at the PA12 phase as indicated by TEM, but the presence of IL-TFSI also contributes for the localization of CNT in both phases, which may be the reason for the outstanding electrical performance. The CNT/IL interactions were also investigated by Raman spectroscopy.

High Performance, Tunable Electrically Small Antennas through Mechanically Guided 3D Assembly.

To address demands for increased data transmission rates, electrically small antennas (ESAs) that simultaneously offer large frequency bandwidths and small physical sizes are of growing interest. 3D layouts are particularly important in this context and among various 3D ESAs, systems that adopt hemispherical shapes are very promising, because they can occupy the entire Chu-sphere and offer outstanding electrical performance. Researchers have developed a few different approaches to fabricate high-quality hemispherical ESAs, but most have static layouts and fixed operating frequencies. Here, a mechanically guided 3D assembly approach is introduced for the design and fabrication of deformable hemispherical ESAs that can offer tunable, dynamic properties to adapt to changes in environmental conditions. The strategy exploits controlled compressive buckling of strategically patterned 2D precursor structures, as a low-cost and high-yield scheme that can exploit conventional, planar processing technologies and commercially available platforms. Combined numerical simulations and experimental measurements show outstanding performance characteristics in terms of the quality factor and radiation efficiency. Application of external tensile strains to elastomeric substrates for these systems allows them to be reshaped and reversibly tuned through a wide range of center frequencies. Mechanical testing under different loading conditions demonstrates the ability of these ESAs to accommodate large deformations.

Organic–Inorganic Heterojunctions toward High‐Performance Ambipolar Field‐Effect Transistor Applications

AbstractThis work reports on combination of organic–inorganic heterojunctions between amorphous indium–gallium–zinc oxide (a‐IGZO) and organic semiconductors for design of high‐performance ambipolar transistors. A vertically sequential layer device configuration that the organic small molecule dinaphtho‐thieno‐thiophene (DNTT) and dioctylbenzothieno[2,3‐b]benzothiophene (C8‐BTBT) are directly vacuum deposited on the surface of a‐IGZO without any interface modification is employed in ambipolar transistors. The ambipolar transistors based on C8‐BTBT/a‐IGZO featured with V‐shaped transfer curves exhibit an outstanding electrical performance with mobilities as high as 5.1 and 4.5 cm2 V−1 s−1 for electrons and holes, respectively. The formation of N‐type channel even if covered with several tens of nanometers thick small molecule film is clarified with the charge injection mechanisms based on both thermionic injection and/or tunneling transport processes. High‐performance ambipolar inverter with extremely large gain of 124 V/V is fabricated based on the C8‐BTBT/a‐IGZO ambipolar transistors. Moreover, a single‐transistor frequency doubler shows high spectral purity with 70% of the output energy at the doubling frequency of 2 kHz. The present work provides a strategy for manufacturing high‐performance ambipolar transistor with straightforward processing approaches, which may help deepen the understanding of ambipolar channel's working mechanisms and optimize the design procedures of logic electrical components.

Fabrication of Flexible Image Sensor Based on Lateral NIPIN Phototransistors.

Flexible photodetectors have been intensely studied for the use of curved image sensors, which are a crucial component in bio-inspired imaging systems, but several challenging points remain, such as a low absorption efficiency due to a thin active layer and low flexibility. We present an advanced method to fabricate a flexible phototransistor array with an improved electrical performance. The outstanding electrical performance is driven by a low dark current owing to deep impurity doping. Stretchable and flexible metal interconnectors simultaneously offer electrical and mechanical stabilities in a highly deformed state. The protocol explicitly describes the fabrication process of the phototransistor using a thin silicon membrane. By measuring I-V characteristics of the completed device in deformed states, we demonstrate that this approach improves the mechanical and electrical stabilities of the phototransistor array. We expect that this approach to a flexible phototransistor can be widely used for the applications of not only next-generation imaging systems/optoelectronics but also wearable devices such as tactile/pressure/temperature sensors and health monitors.

An Inkjet-Printed Low-Voltage Latch Based on Inorganic Electrolyte-Gated Transistors

Printed electronics is a fast-growing emerging technology, which is expected to play a major role in smart sensors for the Internet of Things domain. While there has been considerable progress at the device level by new materials, on circuit level results are still rare. In this letter, we report on the design, simulation, fabrication, and measurement of an inkjet-printed latch, which is an essential building block for digital circuits. Our technology approach is based on electrolyte-gated transistors, which enables low-voltage operation and yields an outstanding electrical performance due to high mobility of the semiconducting, precursor-made In2O3 channel. The fabricated latch can operate reliably down to 0.6 V, where the power consumption is only 16 $\mu \text{W}$ . The area requirement is about 7 mm2, and in terms of lifetime, no performance degradation was observed during an experimental period of 12 weeks.

All-fiber hybrid piezoelectric-enhanced triboelectric nanogenerator for wearable gesture monitoring

With the increasing potential of smart clothing, the demand for generating energy directly in the tissue fibers has prompted for increased research in the field of energy harvesters based on wearable nanogenerators. Current challenges remain in the combination of high output performance, functionalization, and importantly wearing comfort. Herein, an all-fiber hybrid piezoelectric-enhanced triboelectric nanogenerator fabricated by electrospinning silk fibroin and poly(vinylidene fluoride) (PVDF) nanofibers on conductive fabrics is presented. Due to the large specific surface area of nanofibers and the extraordinary ability of silk fibroin to donate electrons in triboelectrification, the hybrid nanogenerator shows outstanding electrical performance, with a power density of 310 µW/cm2. This novel all-fiber configuration provides all benefits of ordinary fabrics having flexible appearance and good air permeability, and moreover it can be custom embedded in clothes in any desirable size and shape. Furthermore, the fabricated device allows identifying various types of body motion by a correlation between gesture and corresponding electrical signal. As potential application field, we foresee an autonomous wearable fall alert microsystem for elderly people and persons working in high risk areas.

Direct growth of graphene nanowalls on quartz substrates as transparent conductive electrodes for perovskite solar cells

An effective method to directly produce high-quality graphene nanowalls (GNWs) on quartz substrates was demonstrated using an advanced self-assembled ratio-frequency plasma-enhanced horizontal tube furnace deposition system under different growth times from 60[Formula: see text]s to 150[Formula: see text]s at a substrate temperature of 850[Formula: see text]C without using any catalyst. The synthesized well-connected three-dimensional GNWs feature outstanding electrical and optical performance: the sheet resistance varies from 1053 [Formula: see text]/[Formula: see text] to 342 [Formula: see text]/[Formula: see text], while the corresponding transmittance ranges from 90.4% to 67.8% at a wavelength of 550[Formula: see text]nm under different growth times. We have also demonstrated that GNWs can be used as transparent conductive electrodes for perovskite solar cells. The highest photovoltaic conversion efficiency of 6.93% can be obtained for the GNWs deposited at a growth time of 120[Formula: see text]s. Hence, our study paves a new way of using GNWs as transparent conductive electrodes in perovskite solar cells.

Efficient Suppression of Defects and Charge Trapping in High Density In-Sn-Zn-O Thin Film Transistor Prepared using Microwave-Assisted Sputter.

Amorphous oxide semiconductor-based thin film transistors (TFTs) have been considered as excellent switching elements for driving active-matrix organic light-emitting diodes (AMOLED) owing to their high mobility and process compatibility. However, oxide semiconductors have inherent defects, causing fast transient charge trapping and device instability. For the next-generation displays such as flexible, wearable, or transparent displays, an active semiconductor layer with ultrahigh mobility and high reliability at low deposition temperature is required. Therefore, we introduced high density plasma microwave-assisted (MWA) sputtering method as a promising deposition tool for the formation of high density and high-performance oxide semiconductor films. In this paper, we present the effect of the MWA sputtering method on the defects and fast charge trapping in In-Sn-Zn-O (ITZO) TFTs using various AC device characterization methodologies including fast I-V, pulsed I-V, transient current, low frequency noise, and discharge current analysis. Using these methods, we were able to analyze the charge trapping mechanism and intrinsic electrical characteristics, and extract the subgap density of the states of oxide TFTs quantitatively. In comparison to conventional sputtered ITZO, high density plasma MWA-sputtered ITZO exhibits outstanding electrical performance, negligible charge trapping characteristics and low subgap density of states. High-density plasma MWA sputtering method has high deposition rate even at low working pressure and control the ion bombardment energy, resulting in forming low defect generation in ITZO and presenting high performance ITZO TFT. We expect the proposed high density plasma sputtering method to be applicable to a wide range of oxide semiconductor device applications.

Solution Combustion Synthesis: Low-Temperature Processing for p-Type Cu:NiO Thin Films for Transparent Electronics.

Low-temperature solution processing opens a new window for the fabrication of oxide semiconductors due to its simple, low cost, and large-area uniformity. Herein, by using solution combustion synthesis (SCS), p-type Cu-doped NiO (Cu:NiO) thin films are fabricated at a temperature lower than 150 °C. The light doping of Cu substitutes the Ni site and disperses the valence band of the NiO matrix, leading to an enhanced p-type conductivity. Their integration into thin-film transistors (TFTs) demonstrates typical p-type semiconducting behavior. The optimized Cu5% NiO TFT exhibits outstanding electrical performance with a hole mobility of 1.5 cm2 V-1 s-1 , a large on/off current ratio of ≈104 , and clear switching characteristics under dynamic measurements. The employment of a high-k ZrO2 gate dielectric enables a low operating voltage (≤2 V) of the TFTs, which is critical for portable and battery-driven devices. The construction of a light-emitting-diode driving circuit demonstrates the high current control capability of the resultant TFTs. The achievement of the low-temperature-processed Cu:NiO thin films via SCS not only provides a feasible approach for low-cost flexible p-type oxide electronics but also represents a significant step toward the development of complementary metal-oxide semiconductor circuits.

Fully transparent high performance thin film transistors with bilayer ITO/Al-Sn-Zn-O channel structures fabricated on glass substrate

In this work, fully transparent high performance double-channel indium-tin-oxide/Al–Sn–Zn–O thin-film transistors (ITO/ATZO TFTs) are successfully fabricated on glass by radio frequency (RF) magnetron sputtering. The ITO layer acts as the bottom channel layer to increase the channel carrier concentration. The top ATZO channel layer, which is deposited via high oxygen partial pressure in the sputtering process, is useful to control the minimum off-state current. After annealing, the ITO/ATZO TFT demonstrates outstanding electrical performances, including a high ON/OFF current ratio (Ion/Ioff) of 3.5 × 108, a steep threshold swing (SS) of 142.2 mV/decade, a superior saturation mobility (μsat) of 246.0 cm2/Vs, and a threshold voltage VT of 0.5 V. The operation mechanisms for double-channel structures are also clarified.

Novel flower-like graphene foam directly grown on a nickel template by chemical vapor deposition

Novel dense graphene foams were fabricated by directly growing graphene on nickel templates by chemical vapor deposition. The as-grown graphene foam showed a hierarchical structure consisting of graphene microspheres with nano pores as flower-like morphology. The high quality of the graphene foam was confirmed by Raman spectrum and conductivity measurement as high as 5100 S m−1. To test its potential application in lithium ion battery, the monolithic graphene foam hybridized with TiO2 nanoparticles as anode material was synthesized via atomic layer deposition. The electrode exhibited high specific capacity (204 mAh g−1, 91 mAh g−1) even at high current (20 C, 60 C, respectively, 1 C = 335 mA g−1) with good stability and reversibility. The outstanding electrical performance could be attributed to the flower-like dense porous nanostructure in the graphene foam, which would work not only as a highly conductive host matrix for ion and electron transportation, but also effectively buffer the volume expansion during the lithiation and delithiation process.

The Effect of Graphene and Natural Rubber Content on Mechanical and Electrical Conductivity Properties of Epoxy/Natural Rubber/Graphene Conductive Materials

The effect of graphene and natural rubber content on the mechanical and electrical performance of two- matrix system epoxy/ natural rubber with graphene nano-platelets (GNP) as a conductive nano-filler were investigated. Natural rubber (SMRL) was used as a toughening agent to improve the toughness properties of thermosetting epoxy resins. Graphene nano-platelets which acted as a conductive nano-filler were incorporated into two- matrix system to produced the outstanding electrical performance. There is an insulator to condutor transition at a significantly lower graphene loading to formed percolated pathway for the electron transfer. The percolation threshold were achieved at 0.8 vol% of graphene nano-filler. The result showed an improvement of the fracture toughness of the epoxy resins with the presence of graphene and natural rubber. The XRD result concluded that the conductive materials have intercalated structure.

Synergistic Effect of Clay Platelets and Carbon Nanotubes in Styrene–Butadiene Rubber Nanocomposites

Nanoscale materials have provided a big advantage for enhancing the performance of rubber composites through leading the synergy effects in the physical and chemical properties. Here, the authors prepare hybrid fillers using a simple solution‐based method, based on electrostatic interactive assembly, of hydroxyl‐functionalized exfoliated montmorillonite (FE‐MMT) and cetyl trimethylammonium bromide‐modified multiwall nanotube (MWNT). The driving force of hybridization is due to specific interaction between the positive charge on the MWNT and the negative charge of hydroxyl group on MMT. To improve their dispersion, the obtained hybrid fillers are then co‐coagulated with styrene–butadiene rubber (SBR) latex to prepare elastomeric composites. Homogenous dispersion of the hybrid nanofillers in the SBR matrix results in a remarkable improvement in mechanical properties such as modulus (0.31 MPa) and tensile strength (75 MPa) at low loadings. Moreover, the prepared composite of hybrid nanofillers and rubber in the SBR matrix exhibits outstanding thermal (0.3779 W m−1 K−1) and electrical conductivities (15 kΩ) and gas barrier performance (9.16 × 10−45 m4 s−1 N−1). The synergistic reinforcement of SBR achieved by the combined incorporation of MWNT and MMT makes it ideal for use in conscious tires. This research opens up a wealth of new opportunities to prepare high performance rubber composites for future engineering applications. image

(Invited) Transparent Top Gate Oxide TFT with ITO/Ag/ITO Low Resistance Electrode for the Application to the High Speed Operation Fingerprint Sensor Array in the Touch Panel

Oxide thin film transistor (TFT) and low-resistance electrode are necessary to manufacture transparent and high resolution fingerprint sensor for application to touch panel display. We adopted ITO/Ag/ITO triple layered stack as an electrode according to that inserting thin Ag layer between both sides of ITO layers definitely helps resistance decreases. Through simulation and optimization, we have chosen each thickness of three layers for optimal transmittance and sheet resistance, and developed dry etching conditions. Top gate structured IGZO TFT with triple layered S/D electrode showed outstanding electrical performance and is expected to be applied to transparent display panel.

Sub-10 pW/Hz0.5 room temperature Ni nano-bolometer

In this letter, we report on room temperature Ni nano-bolometers with a measured electrical noise equivalent power of 8.7 pW/Hz0.5 based on air-suspended and self-aligned nano-stack (SiO2/Ni/SiO2) structures, which is an outstanding electrical performance among uncooled micro/nano-bolometers. This result, together with electrical resistances of 172.6 Ω and modulation frequencies of 15–30 kHz, shows that Ni nano-bolometers can be easily coupled to terahertz antennas and are appropriate for fast passive imaging applications.

Graphene-Based FET Detector forE. coliK12 Real-Time Monitoring and Its Theoretical Analysis

This paper presents a theoretical analysis for a graphene-based FET real-time detector of the target bacteriaE. coliK12. The motivation for this study is to design a sensor device for detection of bacteria in food and water in order to guarantee food safety. Graphene is chosen as our material for sensor design, which has outstanding electrical, physical, and optical performance. In our sensor structure, graphene-based solution gate field effect transistor (FET) is the device model; fabrication and functionalization protocol are presented together in this paper. What is more, a real-time signal display system is the accompanied equipment for our designed biosensor device. In this system, the sensor bias current signalIdswould change obviously when the target bacteria are attached to the sensor surface. And the bias currentIdsincreases when theE. coliconcentration increases. In the latter part, a theoretical interpretation of the sensor signal is to explain the bias currentIdsincreasing after theE. coliK12 attachment.

A one-step method to prepare carbon and dielectric composited films featuring a skeleton–skin structure

A one-step and cost-efficient strategy to prepare carbon and dielectric composites with a skeleton–skin structure by a sol–gel method has been proposed. For the model system in the present work, i.e. C–TiO2 composite films, the insight of the wet chemical mechanisms in sols was illustrated by the electrical compensation theory. The structure and carbon crystallization evolutions with annealing process were investigated, demonstrating the nano carbon with an average sp2 cluster size ranging from 1.1nm to 1.4nm. The resultant composite films turn out to be rutile TiO2 skeleton covered by carbon with intimate interfaces. Benefited from this firm composite structure containing nano carbon, the film possesses tunable and outstanding electrical and optical performance. By appropriate handling annealing temperature, the film could present a high extinction coefficient qualified for solar selective absorber, or show a relatively low extinction coefficient and resistivity (about 10−2Ωcm).

Towards low-voltage organic thin film transistors (OTFTs) with solution-processed high-<em>k</em> dielectric and interface engineering

Although impressive progress has been made in improving the performance of organic thin film transistors (OTFTs), the high operation voltage resulting from the low gate capacitance density of traditional SiO2 remains a severe limitation that hinders OTFTs'development in practical applications. In this regard, developing new materials with high-k characteristics at low cost is of great scientific and technological importance in the area of both academia and industry. Here, we introduce a simple solution-based technique to fabricate high-k metal oxide dielectric system (ATO) at low-temperature, which can be used effectively to realize low-voltage operation of OTFTs. On the other hand, it is well known that the properties of the dielectric/semiconductor and electrode/semiconductor interfaces are crucial in controlling the electrical properties of OTFTs. By optimizing the above two interfaces with octadecylphosphonic acid (ODPA) self-assembled monolayer (SAM) and properly modified low-cost Cu, obviously improved device performance is attained in our low-voltage OTFTs. Further more, organic electronic devices on flexible substrates have attracted much attention due to their low-cost, rollability, large-area processability, and so on. Basing on the above results, outstanding electrical performance is achieved in flexible devices. Our studies demonstrate an effective way to realize low-voltage, high-performance OTFTs at low-cost.