Input Power Density Research Articles

Improved Thermal Dissipation in a MoS2 Field-Effect Transistor by Hybrid High-k Dielectric Layers.

Transition metal dichalcogenides like MoS2 have been considered as crucial channel materials beyond silicon to continuously advance transistor scaling down owing to their two-dimensional structure and exceptional electrical properties. However, the undesirable interface morphology and vibrational phonon frequency mismatch between MoS2 and the dielectric layer induce low thermal boundary conductance, resulting in overheating issues and impeding electrical performance improvement in the MoS2 field-effect transistors. Here, we employed hybrid high-k dielectric layers of Al2O3/HfO2 to simultaneously reduce the interfacial thermal resistance and improve device electrical performance. The enhanced contact, greater vibrational phonon overlapping region, and stronger interfacial bonding force between the top Al2O3 layer and MoS2 promote the heat removal efficiency across the interface to the substrate. Under the same input power density, the temperature profile of the MoS2 transistor on the Al2O3/HfO2 has been largely reduced compared to that of the device on HfO2, with a maximum reduction of 49.5 °C. In addition, the field-effect mobility and current of MoS2 devices on the Al2O3/HfO2 high-k dielectric layers have been significantly improved, attributed to the depressed electron scattering and trap states at the interface. The design of the hybrid high-k dielectric layers provides an efficient solution to simultaneously improve the thermal and electrical performance of the two-dimensional devices.

Coal-derived electrically conductive asphalt pavements for snow/ice melting: From laboratory to field

Timely removal of ice and snow from roads is critical to safe, fast, and uninterrupted transportation networks in cold regions. Constructing electrically conductive asphalt pavements to melt the ice and snow on the roads through resistive heating is an emerging alternative technology to traditional snow/ice removal approaches such as utilizing snowplow machines and deicing chemicals. Carbon-based fibers and fillers including carbon fiber and graphite have been widely reported to make electrically conductive hot mix asphalt mixtures for pavement snow/ice-melting applications. This study aimed to develop and demonstrate a novel type of electrically conductive asphalt pavements for snow/ice-melting, which utilizes electrically conductive cold mix asphalt (CMA) mixtures incorporating coal-derived carbon-based coke aggregate as resistive heating elements. Both laboratory experiments and field tests were conducted to investigate the electrical, mechanical, and thermal properties of such electrically conductive asphalt mixtures and pavements. The laboratory experiment results indicated that the electrically conductive CMA mixtures incorporating coke aggregate had sufficiently high electrical conductivity and satisfactory mechanical performance and the pavement prototype slab utilizing a thin layer of such CMA mixtures could successfully raise the pavement surface temperatures to 8.3–11.7 °C from a low temperature of −5 °C with an input power density of 473 W/m2. The field test results showed that the full-scale coal-derived electrically conductive asphalt pavements were able to increase the pavement surface temperatures when electricity was applied, but the magnitude of temperature increase was highly dependent on the power density. Therefore, it is promising to use coke aggregate to construct coal-derived electrically conductive asphalt pavements for snow/ice melting.

Machine learning model to predict rate constants for sonochemical degradation of organic pollutants

In this study, machine learning (ML) algorithms were employed to predict the pseudo-1st-order reaction rate constants for the sonochemical degradation of aqueous organic pollutants under various conditions. A total of 618 sets of data, including ultrasonic, solution, and pollutant characteristics, were collected from 89 previous studies. Considering the difference between the electrical power (Pele) and calorimetric power (Pcal), the collected data were divided into two groups: data with Pele and data with Pcal. Eight input variables, including frequency, power density, pH, temperature, initial concentration, solubility, vapor pressure, and octanol–water partition coefficient (Kow), and one target variable of the degradation rate constant, were selected for ML. Statistical analysis was conducted, and outliers were determined separately for the two groups. ML models, including random forest (RF), extreme gradient boosting (XGB), and light gradient boosting machine (LGB), were used to predict the pseudo-1st-order reaction rate constants for the removal of aqueous pollutants. The prediction performance of the ML models was evaluated using different metrics, including the root mean squared error (RMSE), mean absolute error (MAE), and R squared (R2). A significantly higher prediction performance was obtained using data without outliers and augmented data. Consequently, all the applied ML models could be used to predict the sonochemical degradation of aqueous pollutants, and the XGB model showed the highest accuracy in predicting the rate constants. In addition, the power density and frequency were the most influential factors among the eight input variables in prediction with the Shapley additive explanation (SHAP) values method. The degradation rate constants of the two pollutants over a wide frequency range (20–1,000 kHz) were predicted using the trained ML model (XGB) and the prediction results were analyzed.

High Stability and Low Power Nanometric Bio-Objects Trapping through Dielectric-Plasmonic Hybrid Nanobowtie.

Micro and nano-scale manipulation of living matter is crucial in biomedical applications for diagnostics and pharmaceuticals, facilitating disease study, drug assessment, and biomarker identification. Despite advancements, trapping biological nanoparticles remains challenging. Nanotweezer-based strategies, including dielectric and plasmonic configurations, show promise due to their efficiency and stability, minimizing damage without direct contact. Our study uniquely proposes an inverted hybrid dielectric-plasmonic nanobowtie designed to overcome the primary limitations of existing dielectric-plasmonic systems, such as high costs and manufacturing complexity. This novel configuration offers significant advantages for the stable and long-term trapping of biological objects, including strong energy confinement with reduced thermal effects. The metal's efficient light reflection capability results in a significant increase in energy field confinement (EC) within the trapping site, achieving an enhancement of over 90% compared to the value obtained with the dielectric nanobowtie. Numerical simulations confirm the successful trapping of 100 nm viruses, demonstrating a trapping stability greater than 10 and a stiffness of 2.203 fN/nm. This configuration ensures optical forces of approximately 2.96 fN with an input power density of 10 mW/μm2 while preserving the temperature, chemical-biological properties, and shape of the biological sample.

Modeling Study of Chemical Kinetics and Vibrational Excitation in a Volumetric DBD in Humid Air at Atmospheric Pressure

A zero-dimensionl model is developed to study the chemical kinetics of a volumetric dielectric barrier discharge (DBD) reactor operating with humid air at atmospheric pressure. This work focuses on the relation between molecular vibrational excitation, the plasma reactor input power and the number densities of several species that are known to play an important role in biomedical applications (e.g. O3,NO,NO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{O}_{3},\ extrm{NO, NO}_{2}$$\\end{document}, ...). A preliminary study is carried out to observe the influence of water molecules on the electron energy distribution function for different values of water concentration and reduced electric field. A simplified approach is then adopted to quantify the contribution of vibrationally-excited O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{O}_{2}$$\\end{document} molecules to NO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{NO}$$\\end{document} formation. The results obtained using our detailed model suggest that for the physical conditions considered in this work O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{O}_{2}$$\\end{document} vibrational kinetics can be neglected without compromising the overall accuracy of the simulation. Finally, a reaction set is coupled with an equivalent circuit model to simulate the E-I characteristic of a typical DBD reactor. Different simulations were carried out considering different values of the average plasma input power densities. A particular focus was given to the influence of the Zeldovich mechanism on O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{O}_{3}$$\\end{document} and NOX\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{NO}_\ extrm{X}$$\\end{document} production performing simulations where this reaction is not considered. The obtained results are shown and the role of vibrationally excited N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{N}_{2}$$\\end{document} molecules is discussed. The simulation results indicate also that N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{N}_{2}$$\\end{document} vibrational excitation, and more precisely the Zeldovich mechanism, has a larger effect on O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{O}_{3}$$\\end{document} and NOX\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{NO}_\ extrm{X}$$\\end{document} production at intermediate input power levels.

Electric field/current enhanced grain growth behavior of 8mol% Y2O3 stabilized cubic ZrO2 (8Y-CSZ) polycrystals

The effect of the flash event on grain growth behavior was examined in 8 mol% yttria-stabilized cubic zirconia (8Y-CSZ) polycrystals under direct and alternating electric fields/currents. Even at the same specimen temperature, the rate of the grain growth is accelerated in the flash event than in the heat treatment without electric field/current (0 V), suggesting that the non-thermal effect caused additionally under the flash event contributes to the acceleration of the grain growth. Although the grain growth behavior can be characterized by the empirical equation (dtn –d0n = kt) with the same grain growth exponent of n = 3 irrespective of the electric field/current, the activation energy for the grain growth is lowered under the flash event. This suggests that the non-thermal effect caused by the flash event does not affect the mechanism of the grain growth, but would accelerate the rate-controlling process of the grain growth. The non-thermal effects can be further accelerated in fine-grained specimens under the alternating current flash and/or by increasing the input power density. Since the grain growth is rate-controlled by the grain boundary cation diffusivity, the non-thermal effect under the flash event would accelerate the grain boundary cation diffusivities through the formation of excess oxygen vacancies depending on the polarity and the power density.

Spatio-temporal analysis of power deposition and vibrational excitation in pulsed N2 microwave discharges from 1D fluid modelling and experiments

Vibrational excitation of N2 beyond thermodynamic equilibrium enhances the reactivity of this molecule and the production of radicals. Experimentally measured temporal and spatial profiles of gas and vibrational temperature show that strong vibrational non-equilibrium is found in a pulsed microwave discharges at moderate pressure (25 mbar) in pure N2 outside the plasma core and as an effect of power pulsing. A one dimensional radial time-resolved self-consistent fluid model has been developed to study the mechanism of formation of vibrationally excited N2. In addition to the temperature maps, time-resolved measurements of spontaneous optical emission, electron density and electron temperature are used to validate the model and the choice of input power density. The model reveals two regions in the plasma: a core where chemistry is dominated by power deposition and where vibrational excitation starts within the first ∼10 µs and an outer region reliant on radial transport, where vibrational excitation is activated slowly during the whole length of the pulse (200 µs). The two regions are separated by a sharp gradient in the estimated deposited power density, which is revealed to be wider than the emission intensity profile used to estimate the plasma size. The low concentration of excited species outside the core prevents the gas from heating and the reduced quenching rates prevent the destruction of vibrationally excited N2, thereby maintaining the observed high non-equilibrium.

Low-frequency magnetoelectric capacitively-coupled receiving antenna with enhanced transmission stabilities under low input power density

Exploiting a more stabilized transmission strategy in magnetoelectric (ME) antennas for near-field communication under lower input power density is still challenging since the strain-mediated ME voltage is easily vulnerable to ambient interferences with significant anisotropy. In this work, a low-frequency (LF) receiving ME antenna system, consisting of transmitting coil and Ni0.8Zn0.2Sm0.02Fe1.98O4/PZT/Ni0.8Zn0.2Sm0.02Fe1.98O4 ME laminate, was proposed and established with the quasi-isotropic response, enhanced stabilities and limit of detection (LOD) of communication distance by capacitively-coupled mode. Experimental results showed that a more uniform receiving response in capacitance with 360° rotating of the ME antenna by a nearly circular response. Transmission stabilities were further evaluated by continuous collected data for 100 min, a near-flat capacitance response with standard Gaussian distribution (μ = 27.48nF and σ2 = 6.37 × 10−6nF) was obtained, and the estimated uncertainty shows one order of magnitude lower than that of voltage capturing mode. Under lower input power density of 15 μW/cm3, comparison studies of the LOD in transmission distance of the ME antennas were implemented, and the maximum effective communication distance of 100 cm for the ME antenna can be reached. The findings provide the possibility of using capacitively-coupled receiving mode of the ME antenna with enhanced stabilities under low input power density.

Low power density, high-efficiency reflective Raman system for polymer SERS substrates.

Surface-enhanced Raman spectroscopy (SERS) is a powerful measurement method in the chemical analysis field. It is much superior to bulk Raman owing to the enhancement of signal sensitivity from the SERS substrate. Nevertheless, the delicate SERS substrates are overpriced, which results in the difficulty of universal measurements. Accordingly, opting for a substrate made of polymer material based on the nanoimprint technique shows great potential for low-cost and high-performance SERS substrates. However, due to its low heat conductivity, the polymer's thermal properties may cause heat to concentrate on the incident spot and damage the nanostructures or analytes. In this article, we proposed a novel design of the Reflective Raman (RR) system to reduce the input power density and maintain high collection efficiency at the same time. The proposed RR system was directly compared with a traditional micro Raman (μ-Raman) system and demonstrated its outstanding performance for low damage threshold analytes and SERS substrates.

Effect of carbon fiber bundles spacing on composites and their electrothermal and anti/deicing properties

Ice tends to form on the surface of wind turbine composite blades, compromising the generator performance and service life. In this work, the electrothermal materials carbon fiber/epoxy (CF/EP) were studied and a carbon fiber-multilayer composite (CFMC) with a protective layer, an electrothermal layer and a thermal insulation layer was designed. The optimal distance between carbon fiber bundles was 4.6 mm to ensure a uniform temperature distribution with minor temperature difference. Compare with other electrothermal materials, the CFMC reached the equilibrium temperature 61.2 °C in 452 s with an input power density of 500 W·m−2. The CFMC also showed excellent anti/deicing capacity and resistance stability in cold environments. The surface temperature climbed from −16 to 0 °C in only 35 s, and the 3 mm thick ice on the surface was removed in 21 mins. The CFMC provides a simple and efficient strategy for anti/deicing composites used in wind turbine blades.

Whole-infrared-band camouflage with dual-band radiative heat dissipation

Advanced multispectral detection technologies have emerged as a significant threat to objects, necessitating the use of multiband camouflage. However, achieving effective camouflage and thermal management across the entire infrared spectrum, especially the short-wave infrared (SWIR) band, remains challenging. This paper proposes a multilayer wavelength-selective emitter that achieves effective camouflage across the entire infrared spectrum, including the near-infrared (NIR), SWIR, mid-wave infrared (MWIR), and long-wave infrared (LWIR) bands, as well as the visible (VIS) band. Furthermore, the emitter enables radiative heat dissipation in two non-atmospheric windows (2.5–3 μm and 5–8 μm). The emitter’s properties are characterized by low emittance of 0.270/0.042/0.218 in the SWIR/MWIR/LWIR bands, and low reflectance of 0.129/0.281 in the VIS/NIR bands. Moreover, the high emittance of 0.742/0.473 in the two non-atmospheric windows ensures efficient radiative heat dissipation, which results in a temperature decrement of 14.4 °C compared to the Cr reference at 2000 W m−2 input power density. This work highlights the role of solar radiance in camouflage, and provides a comprehensive guideline for developing multiband camouflage compatible with radiative heat dissipation, from the visible to LWIR.

Development of a bilayer NiCrAlY/YSZ coating on IN713 LC superalloy by laser cladding

In this study, bilayer laser cladding of Inconel 713LC superalloy was performed by a Nd:YAG laser. Amdry 997 powder was used as the first layer and Metco 204NS ceramic powder as the second layer. The experiments were carried out with different laser parameters to investigate the influence of heat input and laser power density on the microstructure and the hardness of coating. The study revealed that the susceptibility to crack formation in the clad zone increases with the increase in the heat input due to the high cooling rate and intense thermal stress. The formation of shrinkage cavities in the lower half of the clad zone raises with the increase in the heat input owing to reduction in the solidification rate. Microstructural investigations show that a cellular structure is formed at the interface region. The middle area of coating features columnar dendrites, while the upper area of the coating displays very small equiaxed dendrites. The coating mainly comprises γ-Ni, β-NiAl and γ′-Ni3Al phases and the elements of Ni, Co, Cr, Al, Ta, Zr, and Y are homogeneously distributed in the clad zone. As the heat input increases, the microhardness of the samples decreases due to an increase in the dilution ratio. This leads to a decrease of Co, Cr, and Ta elements in the γ′ and the β intermetallic compounds, as well as a reduction of Zr and Y elements in the clad zone.

A dual-band, wide-angle absorbing metasurface for EM energy harvesting and wireless power transfer

In this paper, a dual-band metasurface is designed for electromagnetic (EM) applications in the sub-6G band. The metasurface consists of a hexagonal Complementary Split Ring Resonator (CSRR) absorber array, a dual-band impedance-matched rectifier network, and a load. The CSRR metasurface absorber is designed by combining a hexagonal prism and a hexagonal ring. The proposed absorber is surrounded by metal vias to improve the operating stability of each cell. By integrating the absorber array with the rectification network, the system redundancy and power loss are reduced. The designed metasurface is capable of harvesting EM energy in different frequencies using one port, even at a wide incidence angle. Dual-band rectification within the Sub-6G range is achieved by the rectification network at low input power density. We fabricated and measured a 3 × 3 hexagonal CSRR metasurface array, and the experimental result shows that the optimal input power is 2 dBm (the incident power density is 169 μW/cm2), the radio frequency(RF)-to-direct current(DC) efficiencies are 57.6% and 47% at 3.8 and 5.2 GHz, respectively.

Explaining the decline of US wind output power density

US wind power generation has grown significantly over the last decades, in line with the number and average size of operating turbines. However, wind power density has declined, both measured in terms of wind power output per rotor swept area as well as per spacing area. To study this effect, we present a decomposition of US wind power generation data for the period 2001–2021 and examine how changes in input power density and system efficiency affected output power density. Here, input power density refers to the amount of wind available to turbines, system efficiency refers to the share of power in the wind flowing through rotor swept areas which is converted to electricity and output power density refers to the amount of wind power generated per rotor swept area. We show that, while power input available to turbines has increased in the period 2001–2021, system efficiency has decreased. In total, this has caused a decline in output power density in the last 10 years, explaining higher land-use requirements. The decrease in system efficiency is linked to the decrease in specific power, i.e. the ratio between the nameplate capacity of a turbine and its rotor swept area. Furthermore, we show that the wind available to turbines has increased substantially due to increases in the average hub height of turbines since 2001. However, site quality has slightly decreased in this period.

Sunlight-powered self-excited oscillators for sustainable autonomous soft robotics

As the field of soft robotics advances, full autonomy becomes highly sought after, especially if robot motion can be powered by environmental energy. This would present a self-sustained approach in terms of both energy supply and motion control. Now, autonomous movement can be realized by leveraging out-of-equilibrium oscillatory motion of stimuli-responsive polymers under a constant light source. It would be more advantageous if environmental energy could be scavenged to power robots. However, generating oscillation becomes challenging under the limited power density of available environmental energy sources. Here, we developed fully autonomous soft robots with self-sustainability based on self-excited oscillation. Aided by modeling, we have successfully reduced the required input power density to around one-Sun level through a liquid crystal elastomer (LCE)-based bilayer structure. The autonomous motion of the low-intensity LCE/elastomer bilayer oscillator "LiLBot" under low energy supply was achieved by high photothermal conversion, low modulus, and high material responsiveness simultaneously. The LiLBot features tunable peak-to-peak amplitudes from 4 to 72 degrees and frequencies from 0.3 to 11 hertz. The oscillation approach offers a strategy for designing autonomous, untethered, and sustainable small-scale soft robots, such as a sailboat, walker, roller, and synchronized flapping wings.

Customizable and upgradable design triple-band dual circular polarization rectenna for ambient RF energy harvesting

A Customizable and upgradable design of triple-band dual circular polarization (CP) rectenna is presented for ambient RF energy harvesting of available frequency bands (i.e., 1800, 2.15, 2.42) efficiently. A broadband dual CP receiving antenna is proposed with a broadband impedance matching bandwidth of 123% from 1 to 4.2 GHZ and axial-ratio (AR) bandwidth of 75% from 1.45 to 3.06 GHz with a maximum gain of 5.54 dBi to cover the selected frequency bands. Besides, the proposed triple-band rectifier with a multi-stub impedance matching network is feasible for RF harvesting with the new design method, and the non-dependence of the resonance frequencies on the distance between the stubs, the rectifier can be easily adjusted for other frequencies. The proposed rectenna’s measurement results show that the generated average dc output voltage and conversion efficiency are improved to 0.8 V and 60%, respectively, at a low RF input power density of −2 dBm for a load resistance of 1.5 kΩ.

Rapid and facile preparation of nanocomposite film heaters for composite manufacturing

Nanocomposite film heaters are promising for out-of-oven (OoO) and energy-efficient curing of fiber-reinforced polymer composites. However, the current techniques for manufacturing nanocomposite film heaters are intensive in terms of time and energy and require expensive resources. In this work, we present a facile and rapid approach for preparation of nanocomposite film heaters with excellent heat generation properties based on a frontally polymerizable resin system. This approach enables rapid fabrication of nanocomposite films within a few minutes and without the need for using expensive equipment, making it suitable for mass production of nanocomposite film heaters. Various characterization techniques are used to determine the morphology, composition, and mechanical properties of nanocomposite films. The electrothermal performance of nanocomposite film heaters are then evaluated under various conditions. Nanostructured heaters exhibit excellent Joule heating properties, where temperatures as high as ∼132°C can be reached within only 2 min using a low input power density of ∼2 W cm−2. Finally, a nanocomposite film heater is used for OoO curing of a small composite panel with minimal energy consumption. Using this approach, 0.1 MJ of energy is consumed during the 4-h cure cycle of a commercial prepreg system, which would otherwise require at least 40.5 MJ of energy to cure using a convection oven.

Comprehensive Evaluation of Industrial Potentials for Indoor Organic Photovoltaic Materials via a New Figure of Merit

AbstractAlthough the power conversion efficiencies (PCEs) of indoor organic photovoltaic (IOPV) continue increasing toward the 30% milestone, important factors (e.g., operation stability and cost potential) for industrial application are neglected, thus resulting in a lack of overall top‐down thinking to evaluate the commercialization potential of IOPVs. By introducing five active layer systems to analyze their efficiency–stability–cost gaps, a standardized indoor industrial figure of merit (i‐FOMindoor) concept is proposed as a reliable approach to evaluate their industrial viability. This i‐FOMindoor contains extracted energy density (including PCE, T80 lifetime, and input power density) and material cost (including synthesis complexity and material usage). To inspire a broader interest, the correlations between active layer thickness, efficiency–stability–cost gap, and i‐FOMindoor are also investigated. Impressively, the levelized cost of energy of IOPVs is less sensitive to the active layer thickness in comparison to the outdoor OPVs. Inspired by this i‐FOMindoor, an outdoor i‐FOM is also proposed for industrial potential evaluation of OPV materials in real external environments.

A dual-band, polarization-insensitive, wide-angle metasurface array for electromagnetic energy harvesting and wireless power transfer

A dual-band, polarization-insensitive, wide-angle metasurface array is presented in this article for electromagnetic (EM) energy harvesting in the UMTS-2100 band and Wi-Fi band. The metasurface unit cell is composed of two rings (each with four splits) nested in a centrosymmetric manner. The proposed metasurface array energy harvester consists of periodic array unit cells, a single series diode rectifier, and a load. The design of interconnected unit cells to form energy flow channels enhances the power density of the array terminals, thus improving the ability of the metasurface array to capture energy. In addition, the proposed resonant structure is centrosymmetric, so that consistent and effective collection efficiency can be obtained under different polarizations as well as at wide angular incidence. Moreover, the designed rectifier circuit enables the absorber to rectify dual bands simultaneously at low input power density. The prototype of the finite array is fabricated and tested in an anechoic chamber. The results show that the collection efficiency of the proposed metasurface array can reach 64.8% and 41.1% at two frequencies when the available power density reaches 46.4 μW/cm2.

Achieving relativistically intense X-rays from structured plasma lens

Focusing of high-power X-rays is still a great challenge and the intensity of X-ray attained in existing focusing schemes is still far below the relativistic threshold. Here, we propose that solid density plasma lens can potentially focus X-ray lasers at very high power levels. The interaction of high-power X-ray laser with solid-density plasmas is systematically studied. It is theoretically shown that there exists a certain range of wavelengths for X-ray lasers that can be focused in solid-density plasmas when the input power and plasma density are determined. To avoid the essential laser-plasma instabilities and obtain high-gain intensity amplification for X-ray, we design concave structured plasma lens. Particle-in-cell simulation results show that such regime can effectively avoid the instabilities and focus X-ray of micrometer-sized spot and multi-TW power, and thus lead to the generation of relativistic intensity X-ray. The parameters of the concave structures and the effects of quantum electrodynamics are also discussed and it indicates that our scheme is quite robust. We further demonstrate that the relativistic X-ray laser interacting with thin-foil leads to high-quality attosecond electron bunches.