Increase In Short-circuit Current Research Articles

Distributed Vibration Monitoring System for 10 kV-400 kVA 3D Wound Core Transformer under Progressive Short-Circuit Impulses.

As large-scale, high-proportion, and efficient distribution transformers surge into the grids, anti-short circuit capability testing of transformer windings in efficient distribution seems necessary and prominent. To deeply explore the influence of progressively short-circuit shock impulses on the core winding deformation of efficient power transformers, a finite element theoretical model was built by referring to a three-phase three-winding 3D wound core transformer with a model of S20-MRL-400/10-NX2. The distributions of internal equivalent force and total deformation of the 3D wound core transformer along different paths under progressively short-circuit shock impulses varying from 60% to 120% were investigated. Results show that the equivalent stress and total deformation change rate reach their maximum as the short-circuit current increases from 60% to 80%, and the maximum and average variation rate for the equivalent stress reach 177.75% and 177.43%, while the maximum and average variation rate for the total deformation corresponds to 178.30% and 177.45%, respectively. Meanwhile, the maximum equivalent stress and maximum total deformation reach 29.81 MPa and 38.70 μm, respectively, as the applied short-circuit current increased to 120%. In light of the above observations, the optimization and deployment of wireless sensor nodes was suggested. Therefore, a distributed monitoring system was developed for acquiring the vibration status of the windings in a 3D wound core transformer, which is a beneficial supplement to the traditional short-circuit reactance detection methods for an efficient grid access spot-check of distribution transformers.

Polyvinyl Chloride-Based Luminescent Downshifting Film with High Flame Retardancy and Excellent UV Resistance for Silicon Solar Cells.

Solar power generation, as a clean energy source, has significant potential for development. This work reports the recent efforts to address the challenge of low power conversion efficiency in photovoltaic devices by proposing the fabrication of a luminescence downshifting layer using polyvinyl chloride (PVC) with added fluorescent dots to enhance light utilization. A photoluminescent microsphere (HCPAM) is synthesized by cross-linking hexachlorocyclotriphosphazene, 2-iminobenzimidazoline, and polyethyleneimine. Low addition of HCPAM can improve the fire safety of PVC films, raising the limiting oxygen index of PVC to 32.4% and reducing the total heat release and smoke production rate values by 14.5% and 42.9%, respectively. Additionally, modified PVC film remains a transparency of 88% and shows down-conversion light properties. When the PVC+1%HCPAM film is applied to the solar cell, the short-circuit current density increases from 42.3 to 43.8mAcm-2, resulting in a 7.0% enhancement in power conversion efficiency. HCPAM also effectively delays the photooxidative aging of PVC, particularly at a 3% content, maintaining the surface morphology and optical properties of PVC samples during ultraviolet aging. This study offers an innovative strategy to enhance the fire and UV-resistant performance of PVC films and expand their applications in protecting and efficiently utilizing photovoltaic devices.

The role of selectively oxidized graphene and MoS2 in enhancing efficiency of spray-coated bulk heterojunction photoactive layers

This study investigates bulk heterojunction photoactive layers constituted of selectively oxidized graphene (SOG), molybdenum disulfide (MoS2), and poly 3-hexyl thiophene (P3HT) deposited by spray coating. The functionalization of these 2D materials was confirmed by X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and Raman spectroscopy. The results show that functionalized 2D materials significantly modify the surface morphology and roughness of the photoactive layer, reducing agglomeration. Incorporating SOG and MoS2 leads to a 35% increase in theoretical short circuit current, enhancing wavelength absorption and overall efficiency while maintaining transparency. These results highlight the potential of SOG and MoS2 in scalable semi-transparent solar cell applications, paving the way for further advancements in energy generation and aesthetic architectural integration.

Modulating the density of silicon nanowire arrays for high-performance hydrovoltaic devices

Hydrovoltaic devices (HDs) based on silicon nanowire (SiNW) arrays have received intensive attention due to their simple preparation, mature processing technology, and high output power. Investigating the impact of structure parameters of SiNWs on the performance of HDs can guide the optimization of the devices, but related research is still not sufficient. This work studies the effect of the SiNW density on the performance of HDs. SiNW arrays with different densities were prepared by controlling the react time of Si wafers in the seed solution (t seed) in metal-assisted chemical etching. Density of SiNW array gradually decreases with the increase of t seed. HDs were fabricated based on SiNW arrays with different densities. The research results indicate that the open-circuit voltage gradually decreases with increasing t seed, while the short-circuit current first increases and then decreases with increasing t seed. Overall, SiNW devices with t seed of 20 s and 60 s have the best output performance. The difference in output performance of HDs based on SiNWs with different densities is attributed to the difference in the gap sizes between SiNWs, specific surface area of SiNWs, and the number of SiNWs in parallel. This work gives the corresponding relationship between the preparation conditions of SiNWs, array density, and output performance of hydrovoltaic devices. Density parameters of SiNW arrays with optimized output performance and corresponding preparation conditions are revealed. The relevant results have important reference value for understanding the mechanism of HDs and designing structural parameters of SiNWs for high-performance hydrovoltaic devices.

Efficient Tin-Based Perovskite Solar Cell with a Cesium Acetate Pre-buried PEDOT:PSS Hole Transport Layer.

The strong Lewis acid tin halide leads to an excessively fast crystallization rate, resulting in more defects in the film and degraded device performance. In this work, a cesium acetate (CsAc) pre-buried poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer acts as nucleation points during the crystallization of tin-based perovskite, which can induce preferential orientation growth of crystals and increase the grain size to improve the quality of crystallization. The addition of CsAc not only can increase the conductivity of PEDOT:PSS but also can improve the wettability of the perovskite precursor solution to enhance the interface contact between the hole transport layer and perovskite layer. Because of the incorporation of CsAc in PEDOT:PSS, the average short-circuit current density increases from 23.80 to 27.60 mA cm-2. Furthermore, a power conversion efficiency of 10.99% is achieved for a tin-based perovskite solar cell with CsAc-doped PEDOT:PSS as the hole transport layer.

Vibration-coupled TENGs from weak to ultra-strong induced by vortex for harvesting low-grade airflow energy

Multi-direction, irregularity, low-grade, the dynamic characteristics of low-grade airflow energy are prominent that making it difficult to collect. Here, we propose a vibration-coupled triboelectric nanogenerator (VC-TENG) induced by vortex to achieve from weak to ultra-strong vibration, thus effectively converting low-grade airflow energy into vibrational mechanical energy, and then electric energy. The transferred charge and short-circuit current increases is 47 and 26.9 times due to designed vortex structure, and the resonant response time is 2 s at a speed of 4.1 m/s. A VC-TENG unit delivers a peak power of 4.5 mW under a load resistance of 500 MΩ. A grouping of applied demonstrations of self-powered system validates the practicality and durability of VC-TENG. This work offers a practical strategy for harvesting low-grade airflow energy, and is a promising distributed power technologies for self-powered monitoring and forecasting system in the wild.

Self-Powered TENG with High Humidity Sensitivity from PVA Film Modified by LiCl and MXene.

Triboelectric nanogenerators (TENGs) are promising for a variety of applications that require a reliable output performance and stability. In this work, by utilizing the synergistic effect of lithium chloride (LiCl) and MXene, poly(vinyl alcohol) (PVA) based composite films with humidity-sensitive properties were prepared and employed as a friction layer to achieve self-powered TENGs with enhanced output performance under high humidity. The composite material demonstrates exceptional and stable output performance in the humidity range of 30-95% while exhibiting a strong linear correlation with increasing relative humidity (RH). At 95% RH, its short-circuit current increases up to 31.91 μA, which is three times the output of the TENG fabricated by PVA and PTFE (P-TENG). The rich hydroxyl group in PVA, the strong hygroscopicity of LiCl, and the microcapacitor network provided by MXene nanosheets significantly improve the water absorption capacity and surface roughness of the composite material, resulting in an excellent triboelectric output of TENG. Short-circuit current of the TENG in a wide range of RH (from 50% to 98%) responds very sensitively to humidity fluctuations in the environment and superior adsorption-desorption performance as humidity decreases. Furthermore, TENG regarded as a power supply in high humidity conditions was realized and it can light up 240 LEDs instantaneously with the transfer charge density of TENG reaching 194.37 μC m-2. This technology presents an effective method for stable energy harvesting and self-powered sensing in fog, the ocean, and other high-humidity environments.

The Impact of a 1.1 MWp PV Rooftop Integration in Medium Voltage Distribution Networks

A high penetrating the capacity of Rooftop PLTS has an impact on the performance of distribution network operations and the prior technical studies only using simulation. This paper examines the impact of integrating a 1.1 MWp PV Rooftop into the medium voltage distribution network, involves a comparison between simulation data obtained using the ETAP software, before and after integration, compared with direct measurements. The results indicate improvements in the distribution operating performance. Following the integration, there was a 0.05% increase in voltage levels, a 0.06% increase in short circuit current, a 1.25% reduction in network losses, up to 8.9% harmonics current, up to 0.14% harmonics voltage, and a 0.28% decrease in power factor, as observed at both the substation and the network, they are in accordance with the measurement results.

Electronic structure of P-type amorphous silicon nanowires

Silicon nanowires can improve broadband optical absorption and reduce the radial carrier collection distance in solar cell devices. The disordered nanowire arrays grown by the Plasma-Enhanced Chemical Vapor Deposition method are attractive because they can be embedded on low-cost substrates such as glass, and are compatible with large areas. Here, we experimentally demonstrate that reactive Hydrogen ions with increasing concentrations are doped to construct nanowire architectures in amorphous silicon solar cells. Similar to our investigated planar a-Si: H layers, the amorphous silicon nanowires exhibit a loss function coefficient of about 105/cm. From the reflectivity function, it can be shown that the nanostructures can offer a reliable carrier pool. Our results show that the addition of nanowires can increase the efficiency of a-Si solar cells from 1.11% to 1.57%. The input-photon-to-current conversion efficiency spectrum shows effective carrier collection from 1.2 to 2.2 eV of incident light and the nanowire devices show an increase in short-circuit current of 15% with amorphous Si and 26% with nanocrystalline Si compared to planar devices appropriate.

Enhanced photoelectrochemical performance of mesoporous TiO2 photoanode prepared by multi-step evaporation-induced self-assembly method

Mesoporous TiO2 films are promising in photocatalysis and photoelectrochemistry for energy and environment applications, because of its high specific surface area and regular mesopore structure. However, the performances of mesoporous TiO2 films are still limited by low catalyst loading due to the damage during the preparation process. In this study, a multi-step evaporation-induced self-assembly method is proposed to develop a mesoporous TiO2 photoanode with high catalyst loading. The prepared mesoporous TiO2 photoanodes possess not only high catalyst loading without damage but also large specific surface area, which provides more active sites. Moreover, regular mesopore structure is remained to benefit mass transport. Because of these merits, the mesoporous TiO2 photoanode prepared by the multi-step evaporation-induced self-assembly method exhibits superior performance than does conventional nanoparticles-packed TiO2 photoanode. The superiority of the mesoporous TiO2 photoanode prepared by this multi-step evaporation-induced self-assembly method is also demonstrated by incorporating it into a photocatalytic fuel cell. The short circuit current density and maximum power density increase by 90.9% and 25.0%, respectively. The present work provides a new way to prepare high-performance mesoporous TiO2 films for various photocatalytic and photoelectrochemical applications.

Effect of UV and IR Radiation on the Electrical Characteristics of Ga2O3/ZnGeP2 Hetero-Structures

The data on electrical and photoelectric characteristics of Ga2O3/ZnGeP2 hetero-structures formed by RF magnetron sputtering Ga2O3 target with a purity of (99.99%) were obtained. The samples are sensitive to UV radiation with a wavelength of λ = 254 nm and are able to work offline as detectors of short-wave radiation. Structures with Ga2O3 film that was not annealed at 400 °C show weak sensitivity to long-wavelength radiation, including white light and near-IR (λ = 808 and 1064 nm). After annealing in an air environment (400 °C, 30 min), ZnGeP2 crystals in contact with Ga2O3 show n-type conductivity semiconductor properties, the sensitivity of Ga2O3/ZnGeP2 hetero-structures increases in the UV and IR ranges; the photovoltaic effect is preserved. Under λ = 254 nm illumination, the open-circuit voltage is fixed at positive potentials on the electrode to Ga2O3, the short-circuit current increases by three orders of magnitude, and the responsivity increases by an order of magnitude. The structures detect the photovoltaic effect in the near-IR range and are able to work offline (remotely) as detectors of long-wavelength radiation.

Evaluation of Voltage Stability in Microgrid-Tied Photovoltaic Systems

These days, with the significant increase in the use of renewable energy sources as additional energy sources connected to the distribution network, many challenges and difficulties arise in ensuring sustainability and reliability. The generation, transmission and distribution, in the current state of the electricity system, are facing quite dynamic changes. They are the result of the liberalization of the energy market, the increased use of renewable energy sources such as photovoltaic systems, wind turbines and the charging stations for hybrid and electric vehicles. The most important factors are related to the balancing of the energy system, the analysis of voltage stability, overcoming the consequences of the increase in short-circuit currents, increasing the transmission capacities of the system forming and distribution networks, as well as the accurate forecasting of the development of loads and consumption over the coming years. This article presents an analysis of the voltage stability in a smart microgrid for two different scenarios. The studied cases describe a linear low-voltage p-type microgrid with loads connected to it at different nodes. Data on the type and cross-section of the conductors of the studied power line are presented. Simulation studies were carried out to determine the limits of grid voltage stability when connecting photovoltaic plants with a set power. The simulation results are commented on and an analysis of the optimal operating mode of the system is realized. The model studies were implemented in the NEPLAN program environment. The research carried out allows an evaluation of the permissible limits for network stability when connecting photovoltaic plants. Through this evaluation, it can be determined how many and at which node the loads should be connected without causing an imbalance in the network. This is useful from the point of view of ensuring the sustainability and reliability of electrical energy in a microgrid.

SCAPS simulation and DFT study of lead-free perovskite solar cells based on CsGeI3

With the rapid development of perovskite solar cells (PSCs), environmentally friendly germanium-based PSCs have begun to appear in people's vision. We have designed a perovskite solar cell structure consisting of FTO/Cd0.5Zn0.5S/CsGeI3/MoO3/Au. Our study focused on analyzing the impact of various factors such as the absorption layer, electron transport layer (ETL), hole transport layer (HTL), interfacial defect layer (IDL), and temperature, on device performance. We optimized various parameters of the device, and as a result, the final PCE reached an impressive 35.91%. In addition, we conducted an analysis of the perovskite absorber layer using density functional theory (DFT) and investigated the function of Ge atoms in the perovskite absorber layer. The results show that, for HTL, altering the doping concentration of the ETL has a more significant impact on PSCs. When the operating temperature exceeds 300K, only the short-circuit current (Jsc) increases. When the defect density exceeds 1013cm−3, the rate of carrier recombination begins to increase significantly, along with the interface defect layer. We also analyzed the energy band, density of states, charge density difference, charge population, and elastic constants of the absorption layer using density functional theory (DFT). The results indicate that Ge atoms play a crucial role in photon absorption and photocurrent generation, which is a significant factor contributing to the high power conversion efficiency of germanium-based PSCs. Due to the transfer of electric charge from the Ge atom to the periphery of the I atom and the hybridization between the Ge-4p and I-5p orbitals, the Ge–I bond is formed and stabilized. Finally, the calculation of elastic constants shows that CsGeI3 is a stable mechanical structure.

High current implementation of Cu/P-type GaN triboelectric nanogenerator

Traditional surface engineering, as a means of manufacturing triboelectric nanogenerator (TENG), is complex and expensive. The yield of traditional polymer process is low, which leads to the high cost and low stability of traditional TENGs and greatly limits their practical applications. Moreover, it is worth noting that with the miniaturization and integration of electronic devices, generators need to provide higher current in parallel circuits. In this study, we report the performance of the enhanced Cu/P-type GaN TENG contacts in centimeter scale. Considering the high surface mechanical strength and surface structure characteristics of GaN wafers, we propose using molten KOH to etch the Ga polar GaN surface to form more interface electrons and dangling bonds without destroying the surface structure. Our experimental results show that the generator performance has been drastically improved (the short circuit current increases from 9 to 80 μA, and the open circuit voltage increases from 8 to 29 V). The maximum load electric power density of ∼0.28 W/m2 was obtained. We also compared the open circuit current density with the reported different type TENGs based on Schottky contact at the centimeter-level. The Cu/P-type GaN TENGs achieved in this work exhibit excellent open circuit current density of ∼36 μA/cm2. Thus, we provide insight into surface engineering for future generation TENG devices.

EFFECTS OF LIGHT INTENSITY LEVEL, ILLUMINANCE DEPTH AND TEMPERATURE ON THE PARAMETERS OF A SILICON SOLAR CELL IN CURRENT- GENERATING MODE

The influence of the light intensity level, of illuminance depth and of temperature on some parameters of a silicon solar cell operating in the vicinity of the short-circuit has been the subject of our study.Starting from the continuity equation, then from the equation of the density of minority charge carriers where the effects were studied, we have analyzed the performance parameters according to a temperature range from and under an illumination from to Sun.The results indicate that the illumination intensity has a dominant effect on the current parameters.The photocurrent density and the short-circuit current increase with increasing light intensity level whereas the shunt resistance is more sensitive to temperature variations.

Intestinal enteroendocrine cells rely on ryanodine and IP3 calcium store receptors for mechanotransduction.

Enteroendocrine cells (EECs) are specialized sensors of luminal forces and chemicals in the gastrointestinal (GI) epithelium that respond to stimulation with a release of signalling molecules such as serotonin (5-HT). For mechanosensitive EECs, force activates Piezo2 channels, which generate a very rapidly activating and inactivating (∼10ms) cationic (Na+ , K+ , Ca2+ ) receptor current. Piezo2 receptor currents lead to a large and persistent increase in intracellular calcium (Ca2+ ) that lasts many seconds to sometimes minutes, suggesting signal amplification. However, intracellular calcium dynamics in EEC mechanotransduction remain poorly understood. The aim of this study was to determine the role of Ca2+ stores in EEC mechanotransduction. Mechanical stimulation of a human EEC cell model (QGP-1) resulted in a rapid increase in cytoplasmic Ca2+ and a slower decrease in ER stores Ca2+ , suggesting the involvement of intracellular Ca2+ stores. Comparing murine primary colonic EECs with colonocytes showed expression of intercellular Ca2+ store receptors, a similar expression of IP3 receptors, but a >30-fold enriched expression of Ryr3 in EECs. In mechanically stimulated primary EECs, Ca2+ responses decreased dramatically by emptying stores and pharmacologically blocking IP3 and RyR1/3 receptors. RyR3 genetic knockdown by siRNA led to a significant decrease in mechanosensitive Ca2+ responses and 5-HT release. In tissue, pressure-induced increase in the Ussing short circuit current was significantly decreased by ryanodine receptor blockade. Our data show that mechanosensitive EECs use intracellular Ca2+ stores to amplify mechanically induced Ca2+ entry, with RyR3 receptors selectively expressed in EECs and involved in Ca2+ signalling, 5-HT release and epithelial secretion. KEY POINTS: A population of enteroendocrine cells (EECs) are specialized mechanosensors of the gastrointestinal (GI) epithelium that respond to mechanical stimulation with the release of important signalling molecules such as serotonin. Mechanical activation of these EECs leads to an increase in intracellular calcium (Ca2+ ) with a longer duration than the stimulus, suggesting intracellular Ca2+ signal amplification. In this study, we profiled the expression of intracellular Ca2+ store receptors and found an enriched expression of the intracellular Ca2+ receptor Ryr3, which contributed to the mechanically evoked increases in intracellular calcium, 5-HT release and epithelial secretion. Our data suggest that mechanosensitive EECsrely on intracellular Ca2+ stores and are selective in their use of Ryr3 for amplification of intracellular Ca2+ . This work advances our understanding of EEC mechanotransduction and may provide novel diagnostic and therapeutic targets for GI motility disorders.

Graphitic Carbon Nitride Nanostructures as Molecular Modifier for PEDOT:PSS Hole Transport Layer in Polymer Solar Cells

In this article, we introduced graphitic carbon nitride (g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ), a two-dimensional graphene-like material, tuning electronic properties of PEDOT:PSS via secondary doping. The incorporation of g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> nanosheets (NS) and quantum dots (QDs) to the aqueous solution of PEDOT:PSS weakens the coulombic interaction between PEDOT and PSS chains, leading to the formation of expanded coil/linear conformational structure. Thereby, increasing the conductivity of doped PEDOT:PSS films by 75% and 30%, respectively, for the optimal doping concentrations of NS and QDs. The polymer solar cell employing these films as hole transport layer (HTL) yielded the power conversion efficiency of 7.65% and 6.44% for NS and QDs, respectively, compared to 5.45% for the reference devices with pristine PEDOT:PSS as HTL. This improvement in photovoltaic performance can be attributed to the increase in short circuit current, carrier mobility, fill factor, and reduced series resistance. The reduced contact barrier, owing to smooth NS and QDs modified HTL, facilitates the charge transport by reducing the overall device resistance by 88% and 30% for NS and QDs, respectively. The modification in the molecular structure of PEDOT:PSS because of the incorporation of NS and QDs resulted in improved device stability retaining almost 40% of the initial PCE even after 200 min of continuous illumination. The results demonstrate a systematic strategy of improving the conductivity and mobility of HTL, resulting in enhanced device performance.

Solid-liquid convertible fluorinated terthiophene as additives in mediating morphology and performance of organic solar cells

Specifically, the efficient photovoltaic materials have bithiophene, thieno[3,2-b]thiophene or terthiophene sequences along conjugated backbones. In this contribution, a fluorinated terthiophene derivative ([2F]3T) is developed and used as additive to finely regulate the morphology of bulk heterojunction photoactive layers. Results show that the [2F]3T possess melting point of 75 °C and crystallization temperatures of 35 °C, and thus can serve as nucleation center at room temperature and plasticizer under thermal annealing to form favorable morphology with increased crystallinity and P-i-N like heterojunction. Therefore, the optimized PM6:Y6 based solar cells with [2F]3T additive reach efficiency of 17.6%, which is higher than that of the control devices with a modest efficiency of 16.3%. Moreover, the fill factor (FF) and short circuit current (Jsc) increase significantly from 72.8% and 26.3 mA cm−2 for the control devices to 76.6% and 27.0 mA cm−2 for the devices with [2F]3T additive. Carrier dynamic studies reveal that the favorable morphology in [2F]3T-based devices translate into enhanced charge generation, transportation, and suppressed charge recombination. These findings make clear that the additive featuring with similar chemical building blocks as that of the organic photovoltaic materials has broader implications for further optimization of organic solar cells.

Design of a soft-contact triboelectric nanogenerator for vibrational energy collection and its output performance

Finding renewable energy sources to lower carbon emissions has emerged as a challenge the world faces in the wake of global warming and energy crises. Vibration is a type of mechanical motion common in daily life, and one popular research topic in this regard is how to gather vibrational energy and transform it into electricity. Vibration energy can be collected using triboelectric nanogenerators whose working mechanism is based on contact electrification and electrostatic induction. The COMSOL software is used to simulate the relationship between the voltage across electrodes, transferred charge, and the electrode moving distance (V-Q-X) of triboelectric nanogenerator. Theoretical analysis of the simulation result is offered, along with a brief description of the simulation procedure. When wool is glued to the inner core aluminum foil, TENG’s output performance is significantly improved, with a maximum open-circuit voltage of 160 V. In addition, TENG’s output performance improves linearly as the vibration frequency and amplitude increase. Specifically, when the vibration frequency rises from 1 to 2.5 Hz, the open-circuit voltage rises from 43 to 100 V, the short-circuit current increases from 0.45 to 1.5 µA, and the peak transfer charge grows from 23 to 46 nC; when the vibration amplitude increases from 30 to 60 mm, the maximum open-circuit voltage increases from 50 to 110 V, the maximum short-circuit current increases from 0.3 to 1.5 µA, and the maximum charge transfer increases from 21 to 54 nC. Durability tests of TENG shows that the soft-contact TENG with wool adhesives is exceptionally durable, with decreased mechanical wear on the contact surface and extended service life. The present work is expected to provide some insight into the working mechanism of low-loss and high-performance TENGs and facilitate their wider adoption.

Experimental optical and structural properties of ZnS, MgF2, Ta2O5, Al2O3 and TiO2 deposited by electron beam evaporation for optimum anti-reflective coating designs

MgF2, ZnS, Ta2O5, Al2O3 and TiO2 are some of the most common dielectric materials actually used in solar cells as anti-reflective coatings. For such purpose, they have been deposited by electron beam evaporation, which is one of the preferred technique in industrial settings. In this work we aim to understand the relationship between their optical and physical properties and deposition parameters and thicknesses, being spectroscopic ellipsometry the main technique used for such issue. MgF2 and ZnS have demonstrated rather good optical quality except for the thinnest samples. For Ta2O5, O2 flow during growth has been revealed as critical parameter for ensuring the proper composition of the layer. Al2O3 samples showed a very important amount of Al hydroxide, which is detrimental of the optical quality of these layers. TiO2 samples have also contamination problems, in this case due to oxygen species and Ti3+ oxide presence. For all these oxides, optical properties are clearly influenced by layer thickness. The layer optical parameters n and k have been determined as a function of wavelength (300–1800 nm) and validated against experimental reflectance and transmittance data. Finally, the impact that the proper knowledge of n and k values have when designing broad-band anti-reflective coatings for III-V multijunction solar cells is quantified in terms of short-circuit current relative increase.