Improvement In Electrical Performance Research Articles

Electrochemical exfoliation of graphene from pencil lead

Addressing an ever-increasing demand for graphene in recent years, simple, accessible, and effective graphene synthesis methods are essential. One of such methods is to use a highly oriented pyrolytic graphite (HOPG) to perform an electrochemical exfoliation. While this is one of the simplest and most cost-effective methods, the limited availability and price of HOPG hinders its usage. Our study proposed a simple and economical electrochemical exfoliation of pencil lead, producing graphene with properties comparable to that produced from HOPG. The electrical properties are determined by depositing graphene onto a screen-printed electrode. Graphene from pencil leads can achieve an electrical resistance as low as 1.86 kΩ, marking over 80% improvement in electrical performance compared to bare electrodes. This finding provides an alternative for the synthesis of graphene, increasing its availability and the cost-effectiveness as well as contributing towards a potential commercialization of the method in the future.

Improvement of electrical performance in Normally-Off GaN MOSFET with regrown AlGaN layer on the Source/Drain region

A normally-off GaN MOSFET is successfully fabricated by using the selective regrowth technique (SRT) with regrown AlGaN layer on source/drain (S/D) region. The GaN MOSFET with regrown AlGaN layer and Lg of 10 μm shows enhanced electrical performance such as maximum drain current (ID,max) of 57 mA/mm, maximum transconductance (gm,max) of 11 mS/mm, and field-effect mobility (μFE) of 59 cm2/V·s, respectively, compared to the GaN MOSFET with n+-GaN selective regrowth in S/D region. This is because of the high 2DEG density formed by AlGaN/GaN heterojunction in S/D region. Moreover, to accommodate the poor structural quality of the narrow region regrowth of AlGaN layer on the S/D region, wide regrown AlGaN layer is applied to the GaN MOSFET. Especially, the off-state breakdown voltage improves from 25 V to 192 V with the improved structural quality of wide regrown AlGaN layer and optimized structure and the application of the 70-nm thick SiO2 passivation. These result shows that GaN MOSFET with wide regrown AlGaN layer on S/D region is beneficial to achieving high-quality and uniform normally-off GaN MOSFETs with excellent electrical performance.

P‐156: Efficiency Improvement Mechanism Analysis of Sidewall Passivation GaN based Micro‐LEDs by Atomic Layer Deposition

Sidewall passivation using atomic layer deposition (ALD) can efficiently improve external quantum efficiency (EQE). Such treatment increases EQE, a combination of internal quantum efficiency (IQE) and light extraction efficiency (LEE), primarily by curtailing surface recombination according to the ABC model. Determined by the ratio of radiative recombination rate to total recombination rate, the IQE of an LED holds a significant correlation with the diode's ideality factor in the Shockley model. In this paper, we analysis the mechanism of ALD sidewall passivation enhancing device performance in detail from the aspects of electrical performance improvement and optical performance improvement.

High-Entropy Strategy to Achieve Electronic Band Convergence for High-Performance Thermoelectrics.

Multiband convergence has attracted significant interest due to its positive effects on further improving thermoelectric performance. However, the current research mainly focuses on two- or three-band convergence in lead chalcogenides through doping and alloying. Therefore, exploring a new strategy to facilitate more-band convergence has instructive significance and practical value in thermoelectric research. Herein, we first propose a high-entropy strategy to achieve four-band convergence for optimizing thermoelectric performance. Taking high-entropy AgSbPbSnGeTe5 as an example, we found that the emergence of more-band convergence occurs as the configuration entropy increases; in particular, the four-band convergence occurs in high-entropy AgSbPbSnGeTe5. The overlap of multiatom orbitals in the high-entropy sample contributes to the convergence of four valence bands, promoting the improvement of electrical performance. Meanwhile, due to large lattice distortion and disordered atoms, the phonon mean free path is effectively compressed, resulting in low lattice thermal conductivity of high-entropy AgSbPbSnGeTe5. Consequently, AgSbPbSnGeTe5 achieved an intrinsically high ZT value of 1.22 at 673 K, providing a cornerstone for further optimizing thermoelectric performance. For example, by generally optimizing the carrier concentration, a peak ZT value of ∼1.75 at 723 K is achieved. These insights offer a comprehensive understanding of the band structure affected by unique structures of high-entropy materials and also shed useful light on innovation mechanisms and functionalities for future improvement of thermoelectric performance.

Conceptual design and preliminary experimental study on curved PV ventilated facade assisted heat pump system (CPVF-HP)

Integrating photovoltaic PV with curved architecture boosts renewable energy use and reduces carbon emissions in building applications. This paper proposes a curved PV ventilated facade assisted heat pump system (CPVF-HP), utilizing curved PV ventilation facade as carrier for the application of PV in curved buildings, and enhancing overall energy efficiency through synergistic operation with heat pumps. In the cooling mode, the system employs the heat pump evaporator to pre-cool the air entering the curved PV ventilated facade, thereby reducing the temperature of the PV cells and the air conditioning load of the building. In the heating mode, the CPVF-HP system preheats the air entering the heat pump evaporator using the curved PV ventilated facade, elevating the evaporation temperature of the heat pump. The experimental setup of CPVF-HP is established, and the dynamic performance of the CPVF under various ventilation conditions and its synergistic operational performance with the heat pump have been investigated. The results indicate that CPVF displays considerable difference in irradiance and temperature across its east–west orientation, especially noticeable during morning and afternoon hours, affecting the system's electrical performance. Notably, isotropic scattered radiation improves radiation uniformity and the electrical efficiency of CPVF. The system achieves a notable average electrical efficiency increase of 69.90% on cloudy days compared to sunny conditions. CPVF-HP system effectively manages temperatures by precooling or preheating the air, enhancing the electrical efficiency by 34.43% in cooling mode, and increasing COP by 5.23% in heating mode compared to an independent heat pump operation. The CPVF-HP system demonstrates a synergistic improvement in both thermal and electrical performance, offering an innovative approach to optimizing energy efficiency in curved PV integrated buildings.

Improving the overall performance of a hybrid photovoltaic system by reflectors and cooling with water jet

In the present research, the overall performance of the hybrid photovoltaic thermal PVT system used in the production of electric power and water heating has been evaluated. The PVT was coupled with reflectors to increase the energy production and cool it by water jet. The experimental tests were conducted in Iraq – Samarra located at the longitude (43 40 East) and the latitude (34 35 North). Several experiments were carried out through April 2021 in the outdoors. The highest overall instantaneous efficiency was 64%, and the highest percentage improvement in the PVT electrical performance with reflectors was 42.6% at a (0.0084 kg/s) load flow rate. The water temperature in the thermal storage tank increased by about (6°C/6 h) when the electric heater was turned on, while it decreased (6°C/6 h) without turning it on, and it consumed 18.7% of the total batteries energy, which makes it an ideal solution to compensate for the period of sun absence.

Effect of Process Parameters in Additively Manufactured Sensors prepared via Material Extrusion Processes: Correlation among Electrical, Mechanical and Microstructure Properties

Fusion-based Material Extrusion (MEX) Additive Manufacturing (AM) processes have been extensively used for the fabrication of smart structures with embedded sensors, proving to have several benefits such as reduction in cost, manufacturing time, and assembly. A major issue negatively affecting 3D printed sensors is related to their poor electrical conductivity, as well as inconsistent electrical performance, which leads to electrical power losses amongst other issues. In the present paper, a set of process parameters (ironing, printing temperature, and infill overlap) has been analyzed by performing a Design of Experiment (DoE) factorial plan to minimize the electrical resistance. The best process parameters configuration involves a remarkable reduction of electrical resistance of 47.9%, as well as an improvement of mechanical properties of 31.9% (ultimate tensile strength), 25.8% (elongation at break) and 28.14% (flexural stress). The microstructure of the obtained results has also been analyzed by employing a high-resolution, X-ray Computed Tomography (X-Ray CT) system showing a reduction of intralayer voids of 19.5%. This work demonstrates a clear correlation between process parameters and the corresponding electrical properties, mechanical properties, and internal microstructure. In the present research, it has been shown that i) it is possible to significantly improve the overall 3D printed sensors performance by process parameter selection, and ii) small changes in the microstructure lead to remarkable improvements in electrical and mechanical performance.

Improvement of electrical performance of ZnO linear resistors by Y2O3 doping

ZnO-TiO2−MgO-Al2O3 linear resistors with various Y2O3 dopant concentrations were fabricated using the conventional solid-state reaction method. The comprehensive investigation of the impact of Y2O3 addition on the microstructure and electrical characteristics of the resistors was carried out. The results indicated that the Y2O3 phase hindered the growth of zinc oxide particles. Additionally, the incorporation of yttrium oxide increased the linearity of the resistors and affected the height of the grain boundary barrier (φb). Subsequently, a Y2O3-doped ZnO linear resistor with a nonlinearity constant (α) of 1.09 and a resistance-temperature constant (αT) of -2.51 × 10−3/ °C was effectively produced. The comprehensive evaluation of the microstructure and relevant electrical characteristics enables the efficient production of linear resistors with excellent electrical properties.

Synergies and Trade-Offs in Hybrid Propulsion Systems Through Physics-Based Electrical Component Modeling

Abstract Hybrid-electric propulsion is recognized as an enabling technology for reducing aviation's environmental impact. In this work, a serial/parallel hybrid configuration of a 19-passenger commuter aircraft is investigated. Two underwing-mounted turboprop engines are connected to electrical branches via generators. One rear fuselage-mounted electrically driven ducted fan is coupled with an electric motor and respective electrical branch. A battery system completes the selected architecture. Consistency in modeling accuracy of propulsion systems is aimed for by development of an integrated framework. A multipoint synthesis scheme for the gas turbine and electric fan is combined with physics-based analytical modeling for electrical components. Influence of turbomachinery and electrical power system design points on the integrated power system is examined. An opposing trend between electrical and conventional powertrain mass is driven by electric fan design power. Power system efficiency improvements in the order of 2% favor high-power electric fan designs. A trade-off in electrical power system mass and performance arises from oversizing of electrical components for load manipulation. Branch efficiency improvements of up to 3% imply potential to achieve battery mass reduction due to fewer transmission losses. A threshold system voltage of 1 kV, yielding 32% mass reduction of electrical branches and performance improvements of 1–2%, is identified. This work sets the foundation for interpreting mission-level electrification outcomes that are driven by interactions on the integrated power system. Areas of conflicting interests and synergistic opportunities are highlighted for optimal conceptual design of hybrid powertrains.

Intrinsic 1{T}^{{prime} } phase induced in atomically thin 2H-MoTe2 by a single terahertz pulse

The polymorphic transition from 2H to 1{T}^{{prime} }-MoTe2, which was thought to be induced by high-energy photon irradiation among many other means, has been intensely studied for its technological relevance in nanoscale transistors due to the remarkable improvement in electrical performance. However, it remains controversial whether a crystalline 1{T}^{{prime} } phase is produced because optical signatures of this putative transition are found to be associated with the formation of tellurium clusters instead. Here we demonstrate the creation of an intrinsic 1{T}^{{prime} } lattice after irradiating a mono- or few-layer 2H-MoTe2 with a single field-enhanced terahertz pulse. Unlike optical pulses, the low terahertz photon energy limits possible structural damages. We further develop a single-shot terahertz-pump-second-harmonic-probe technique and reveal a transition out of the 2H-phase within 10 ns after photoexcitation. Our results not only provide important insights to resolve the long-standing debate over the light-induced polymorphic transition in MoTe2 but also highlight the unique capability of strong-field terahertz pulses in manipulating quantum materials.

3D printing of conductive polymer aerogel thermoelectric generator with tertiary doping

The rapid advancement of conductive polymer aerogel for thermoelectric application has predominantly depended on the use of performance-enhancing additives for improvement in electrical performance. Meanwhile, the intrinsic capability of the polymer matrix is often overlooked, and control over aerogel geometry remains limited. This arises from the challenges in fabricating conductive polymer aerogel film and the absence of an effective doping technique that does not compromise the aerogel’s fragile microstructure due to induced capillary stress. Herein, 3D printing is combined with a tertiary doping process to simultaneously enable synthesize of conductive polymer aerogel with controlled geometry, high electrical conductivity of over 10 Scm−1, low thermal conductivity of < 100 mWm−1K−1, while increasing the thermoelectric output by four times compared to pristine aerogel. The result of this work opens new opportunities to enhance the performance of conductive polymer without relying on additives by unleashing the full potential for conductive polymer matrix.

Improvement of electrical insulation performance of silicone rubber cables due to exposure to heat and radiation

AbstractThermal treatments, with and without co‐irradiation with gamma rays, were given to safety‐related cables insulated with silicone rubber for nuclear power plants (NPPs). To examine the effects of the above treatments on the insulation properties of the cables, DC voltages were applied to them and the induced changes in leakage current were measured by the current integration method. As a result, it has become clear that the leakage current is the largest in the pristine untreated cable. In addition, almost no leakage current flows in the cables heated at 200°C or 290°C for several hundred hours. The leakage current remains small when the co‐irradiation with gamma rays was given at 100°C or 200°C for relatively long periods exceeding 1000 h. The reason for these results seems to be that the silicone rubber insulation becomes hardened as a result of the thermal or concurrent treatment, and the transport of ionic carriers becomes difficult. The above results indicate experimentally that the degradation is not a matter of great concern for the insulation performance of silicone‐rubber‐insulated safety‐related cables in NPPs.

Improvement in Electrical Performance of Distributed Generation due to Electromagnetic Interference

Improvement in Electrical Performance of Distributed Generation due to Electromagnetic Interference

Optimal DSTATCOM, PVAs and WTGUs allocation for electrical distribution system performance improvement using improved TLBO

Optimal DSTATCOM, PVAs and WTGUs allocation for electrical distribution system performance improvement using improved TLBO

Improvement of electrical performance of Photovoltaic cell with incorporating nanofluid flow as cooling system

The present study is about the modeling of laminar flow of testing fluid within the sinusoidal wall in existence of V shaped fins. The heat absorption of testing fluid has been improved with loading nanoparticles and installing fins within the upper side of the pipe. Heat generation in various layers has been calculated and considered as the source term of conduction equations for each solid layer. The fluid regime within the pipe is laminar and equations have been solved in steady state form. The accuracy of the utilized numerical model has been tested based on data of absorber temperature for the previous article. Grid indecency has been examined and the best size of mesh was obtained. With installing fins, the performances of the system have been improved in both views of electrical (0.1%) and thermal (1.12%). Also, outputs showed that the efficacy of fins on thermal and electrical efficiencies for highest amount of inlet velocity (uin) is 14.30% and 39.75% greater than those of uin = 0.06. Increasing velocity can decrease the cell temperature about 7.4% and thermal performance increase about 17%.

Mitigation of hot-spot effect via back side cooling techniques: A potential for electrical and thermal performance improvement

Hot-spot mitigation is an ever-present issue in photovoltaic system and it significantly affects the performance of photovoltaic (PV) panels. Most of the hot-spots are actually partial hot-spots which cover only a part of PV cell, or part of PV panel. In this work an influence of cooling mechanism on hot-spot mitigation is investigated by using previously developed numerical model. Specific parameters such as insolation, hot-spot intensity, convection intensity, cooling medium temperature and number of affected cells were varied for single panel. By varying parameters, it was found that partial hot-spots with less than 15% shade percentage on up to 4 cells (corresponds with 1% of total shade on PV panel) can be mitigated with adequate cooling technique applied on the PV panel. The hot-spot cases with larger shade can be mitigated, but only with high cooling intensity which makes the feasibility of the mitigation highly questionable. Hot-spot cases with more than 15% shade percentage on more than 10 affected cells (corresponds with 2.5% of total shade on PV panel) practically cannot be completely mitigated with any back side cooling technique. Nevertheless, cooling technique still provides additional electrical energy gain even with intense hot-spot cases. Results gained in this investigation can also be used to estimate potential in higher electricity output with specific cooling technique, and to estimate thermal energy potential such as house or hot water heating. A simplified case study is presented, where result application is explained step-by-step. These results are of particular interest for PV panels installed in urban areas with lots of obstructions and where regular cleaning is not practical. Such applications are rooftop PV systems, facade PV and photovoltaic-thermal (PVT) systems.

Alkali-Doped Nanopaper Membranes Applied as a Gate Dielectric in FETs and Logic Gates with an Enhanced Dynamic Response.

The market for flexible, hybrid, and printed electronic systems, which can appear in everything from sensors and wearables to displays and lighting, is still uncertain. What is clear is that these systems are appearing every day, enabling devices and systems that can, in the near future, be crumpled up and tucked in our pockets. Within this context, cellulose-based modified nanopapers were developed to serve both as a physical support and a gate dielectric layer in field-effect transistors (FETs) that are fully recyclable. It was found that the impregnation of those nanopapers with sodium (Na+) ions allows for low operating voltage FETs (<3 V), with mobility above 10 cm2 V-1 s-1, current modulation surpassing 105, and an improved dynamic response. Thus, it was possible to implement those transistors into simple circuits such as inverters, reaching a clear discrimination between logic states. Besides the overall improvement in electrical performance, these devices have shown to be an interesting alternative for reliable, sustainable, and flexible electronics, maintaining proper operation even under stress conditions.

Probing the electrical performance improvement of FET device based on multilayer MoS2 material

The process quality of material and device can be evaluated by the electrical performance. In this paper, the multi-layer MoS2 material and nickel (Ni) metal were used as channel and electrodes of FET device, which can be fabricated by the electron beam lithography and evaporation processes. The morphology, structure, component and spectral characteristic of multilayer MoS2 material and device were characterized by optical microscope, Raman spectrometer and scanning electron microscope (SEM), and the fabrication feasibility was also discussed. Meanwhile, the electronic performance of device was tested and analyzed by probe table and semiconductor parameter analyzer, and the influence of annealing treatment can also be explored. The contact resistance of device decreases after annealing, current switching ratio increase by one order of magnitude, output characteristic curve shows linear, and the electrical performance can also be improved, which can provide the research guidance for the electronic device based on multilayer MoS2 material.

Optimized weighted mobility induced high thermoelectric performance of ZnO‐based multilayered thin films

AbstractAs a transparent thermoelectric oxide, gallium‐doped zinc oxide (GZO) has the potential to power wearable or portable electronics and may be used in the integrated circuits industry for chip cooling. Constructing ZnO–GZO interfaces has been proposed as an effective strategy for improving thermoelectric performance of GZO thin films. However, without the aid of band structure calculation for multilayered films, it is hard to directly elucidate the underlying mechanisms of carrier transport. Weighted mobility is an indicator that reveals the inherent electronic transport properties like carrier scattering, electronic band structure, and so on. Thus, to further investigate the effects of ZnO–GZO interfaces on electrical properties of GZO thin films, the structures containing different numbers of ZnO–GZO interfaces were designed and the correlations among numbers of ZnO–GZO interfaces, weighted mobility, and electrical properties were explored. It was found that with more ZnO–GZO interfaces, the weighted mobility increased, and the power factor values also improved as well. Consequently, an enhanced power factor value reached 439 μW m−1 K−2 at 623 K. This work demonstrated the beneficial effects of multiple interfaces on the improvements of electrical transport performance through analyzing weighted mobility, which laid a foundation for further optimization of thermoelectric performance.

Vacancy Manipulation Induced Optimal Carrier Concentration, Band Convergence and Low Lattice Thermal Conductivity in Nano‐Crystalline SnTe Yielding Superior Thermoelectric Performance

AbstractSynergetic optimization of electrical and thermal transport properties is achieved for SnTe‐based nano‐crystalline materials. Gd doping is able to suppress the Sn vacancy, which is confirmed by positron annihilation measurements and corresponding theoretical calculations. Hence, the optimal hole carrier concentration is obtained, leading to the improvement of electrical transport performance and simultaneous decrease of electronic thermal conductivity. In addition, the incremental density of states effective mass m* in SnTe is realized by the promotion of the band convergence via Gd doping, which is further confirmed by the band structure calculation. Hence, the enhancement of the Seebeck coefficient is also achieved, leading to a high power factor of 2922 µW m−1 K−2 for Sn0.96Gd0.04Te at 900 K. Meanwhile, substantial suppression of the lattice thermal conductivity is observed in Gd‐doped SnTe, which is originated from enhanced phonon scattering by multiple processes including mass and strain fluctuations due to the Gd doping, scattering of grain boundaries, nano‐pores, and secondary phases induced by Gd doping. With the decreased phonon mean free path and reduced average phonon group velocity, a rather low lattice thermal conductivity is achieved. As a result, the synergetic optimization of the electric and thermal transport properties contributes to a rather high ZT value of ≈1.5 at 900 K, leading to the superior thermoelectric performance of SnTe‐based nanoscale polycrystalline materials.