Commercial Light-emitting Diodes Research Articles

Responses of mustard greens (Brassica juncea L.) to additional lighting duration of LED under greenhouse conditions in the tropical zone

ABSTRACT Light-emitting diodes have been beneficial for plant growth, especially for microgreens in countries with low radiation, greenhouses, and chambers. However, information about how plants respond to additional light-emitting diode lighting after 12 hours of sunlight exposure in tropical areas is limited. This study examines the effects of long-duration light-emitting diodes on mustard greens in Kien Giang province, Vietnam (105°14’33.21” E; 9°91’41.13” N). The trials were conducted in the greenhouse for two growing seasons with a completely randomized design, including 0, 2, 4, and 6 hours of assembled light-emitting diodes lighting and 4 hours of commercial light-emitting diodes lighting after 6 pm, with three replications. Results showed that weather factors in season 2 favorably influenced mustard’s growth. At 4 hours of lighting, commercial light-emitting diodes showed a higher chlorophyll index, flowering time, flowering rate, leaf number, and absolute growth rate of leaf number but less leaf and fresh shoot weight than assembled light-emitting diodes. Four hours of assembled light-emitting diodes positively affected most mustard growth, while 6 hours of assembled light-emitting diodes were superior for flowering aspects. Adding 4 hours of light-emitting diodes could increase leafy yield and shorten the harvesting time of mustard greens grown in greenhouses under tropical conditions.

Impacts of Eu2+ -doped K3LuSi2O7 phosphor and a scattering particle on conventional white light emitting diodes

The K<sub>3</sub>LuSi<sub>2</sub>O<sub>7</sub> phosphor doping Eu2+ rare-earth ions (KLS:Eu) was reported to possess broad emission band from near-ultraviolet to nearinfrared. Additionally, this phosphor showed a wide absorption band of 250-600 nm, allowing it to be excited by blue-light chip of 460 nm, making it one of the suitable phosphor materials for a light emitting diode (LED). Besides, the scattering particle material CaCO<sub>3</sub> is incorporated into the yellow phosphor layer to serve the scattering-enhancement purpose. The combination of both materials aims at accomplishing improvements in performance of commercial LED package. The concentration of KLS:Eu is constant while that of CaCO3 is modified. As a result, the scattering factor is regulated and become the key factor influencing the optical outputs of the simulated LED. The increasing CaCO<sub>3</sub> concentration enhances the phosphor scattering efficiency of light, helping to improve the lumen output and color-temperature consistency of the LED. However, the color rendering performance declines as a function of the CaCO3 growing amount, despite the presence of a KLS:Eu phosphor layer. Further works should be done to optimize the application of KLS:Eu in cooperation with scattering particles for a higher-quality LED device.

Efficient and stable hybrid perovskite-organic light-emitting diodes with external quantum efficiency exceeding 40 per cent

Light-emitting diodes (LEDs) based on perovskite semiconductor materials with tunable emission wavelength in visible light range as well as narrow linewidth are potential competitors among current light-emitting display technologies, but still suffer from severe instability driven by electric field. Here, we develop a stable, efficient and high-color purity hybrid LED with a tandem structure by combining the perovskite LED and the commercial organic LED technologies to accelerate the practical application of perovskites. Perovskite LED and organic LED with close photoluminescence peak are selected to maximize photon emission without photon reabsorption and to achieve the narrowed emission spectra. By designing an efficient interconnecting layer with p-type interface doping that provides good opto-electric coupling and reduces Joule heating, the resulting green emitting hybrid LED shows a narrow linewidth of around 30 nm, a peak luminance of over 176,000 cd m−2, a maximum external quantum efficiency of over 40%, and an operational half-lifetime of over 42,000 h.

A triboelectric nanogenerator based on a spiral rotating shaft for efficient marine energy harvesting of the hydrostatic pressure differential

Equipment used in underwater sensing and exploration typically relies on cables or batteries for energy supply, resulting in a limited and inconvenient energy supply and marine environmental pollution that hinder the sustainable development of distributed ocean sensing networks. Here, we design a deep-sea differential-pressure triboelectric nanogenerator (DP-TENG) based on a spiral shaft drive using modified polymer materials to harness the hydrostatic pressure gradient energy at varying ocean depths to power underwater equipment. The spiral shaft structure converts a single compression into multiple rotations of the TENG rotor, achieving efficient conversion of differential pressure energy. The multi-pair electrode design enables the DP-TENG to generate a peak current of 61.7 μA, the instantaneous current density can reach 0.69 μA cm−2, and the output performance can be improved by optimizing the spiral angle of the shaft. The DP-TENG can charge a 33 μF capacitor to 17.5 V within five working cycles. It can also power a digital calculator and light up 116 commercial power light-emitting diodes, demonstrating excellent output capability. With its simple structure, low production cost, and small form factor, the DP-TENG can be seamlessly integrated with underwater vehicles. The results hold broad prospects for underwater blue energy harvesting and are expected to contribute to the development of self-powered equipment toward emerging “smart ocean” and blue economy applications.

In-situ growth of 3D amorphous Ni-Co-Mn phosphate on 2D Ti3C2Tx nanocomposite for commercial-level hybrid energy storage application

To overcome the limited electronic conductivity and capacity of single and binary transition metal phosphates (TMPs), highly electrochemical active materials and rational structural design of ternary TMPs composite are urgently required. In this study, we successfully synthesized an amorphous 3D Ni-Co-Mn phosphate@2D Ti3C2Tx (MXene) nanocomposite (NCMP series) through the electrodeposition method. The amorphous Ni-Co-Mn phosphate effectively restricts the self-accumulation of MXene nanosheets, resulting in the development of a porous nanostructure. This structure exposes more active sites, expands the ion transport path, and enhances the conductivity of the Ni-Co-Mn phosphate@Ti3C2Tx material. Owing to the synergistic effect offered by Ni-Co-Mn phosphate and MXene nanocomposite, the anchored Ni-Co-Mn phosphate@Ti3C2Tx (NCMP-5) electrode delivers an elevated capacity of 342 mAh/g (1230 C/g) at 5.0 A/g, surpassing the pristine Ni-Co-Mn phosphate (NCMP-4, 260 mAh/g) and MXene (33.3 mAh/g). Moreover, a hybrid solid-state supercapacitor (HSSC) device is assembled with NCMP-5 as a cathode and reduced graphene oxide (rGO) as an anode within a polymer gel (PVA-KOH) electrolyte. Notably, the fabricated HSSC device displays a supreme specific capacity of 27.5 mAh/g (99 C/g) and a high (volumetric) energy density of 22 Wh/kg (3.6 Wh/cm3) at a power density of 0.80 kW/kg (0.13 kW/cm3) for 1.0 A/g. Moreover, the HSSC device retains 95.4 % of its initial capacity even after 10,000 cycles. Importantly, the operational potential window of two serially connected HSSC devices approaches +3.2 V, enabling different colored commercial light-emitting diodes (LEDs) to be efficiently illuminated. Eventually, the remarkable supercapacitive characteristics of the 3D@2D amorphous Ni-Co-Mn phosphate@MXene nanocomposite make it an attractive choice for advanced electroactive materials in upcoming hybrid energy storage technologies.

Nano scattering particle: an approach to improve quality of the commercial led

The light-emitting diodes (LEDs) have emerged as a sustainable illumination solution in the lighting industry. However, the commercial LEDs suffer from low chromatic rendition performance. This work proposes a feasible approach to enhance the quality of commercial LED packages via regulating scattering factors. The TiO2 nano scattering particles are added into the YAG:Ce3+ compound to enhance the internal scattering performance, inducing the blue-light conversion and extraction. In this work, TiO2 concentration varies from 0 wt% to 20 wt%. Results show that 5 wt% of TiO2 is the right concentration to achieve the optimal scattering performance for improvements in luminosity and color rendition of the LED. If the TiO2 concentration is beyond 5 wt%, these two parameters decline owing to too intensive light scattering. Meanwhile, 10 wt% is the most appropriate concentration of TiO2 to enhance the color uniformity of the LED.

Deformable micro-supercapacitor fabricated via laser ablation patterning of Graphene/liquid metal

Deformable and miniaturized energy storage devices are essential for powering soft electronics. Herein, we fabricate deformable micro supercapacitors (MSCs) based on eutectic gallium-indium liquid metal (EGaIn) current collectors with integrated graphene. The well-define interdigitated electrode patterning with controlled gap is successfully realized by using the laser ablation because of a strong laser absorption of graphene and EGaIn. By judicious control of gap size between neighboring interdigitated electrodes and mass loading of graphene, we achieve a high areal capacitance (1336 µF cm−2) with reliable rate performance. In addition, owing to the intrinsic liquid characteristics of EGaIn current collector, the areal capacitance of fabricated MSC retains 90% of original value even after repetitive folding and 20% stretching up to 1000 cycles. Finally, we successfully integrate deformable MSC with a commercial light-emitting diode to demonstrate the feasibility of MSC as a deformable power source. The fabricated MSCs operate stably under various mechanical deformations, including stretching, folding, twisting, and wrinkling.

Improving the performance of triboelectric nanogenerators using flexible polyurethane nanocomposites foam filled with montmorillonite

Flexible polyurethane (FPU) foam is flexible and adaptable, making it a promising candidate for utilization as a triboelectric layer in triboelectric nanogenerator (TENG) devices. Nevertheless, the mechanical properties and output voltages of FPU foam are limited, prompting the need to explore modifications that can enhance its performance. In this study, FPU foam was modified through the incorporation of natural montmorillonite (Na-MMT) nanoclay at different weight ratios (0.1, 0.3, 0.5, and 0.7 wt%), resulting in the development of FPU/Na-MMT nanocomposites. The exfoliation of Na-MMT within the FPU matrix was established using XRD and TEM techniques. Morphology analysis by SEM confirmed that adding Na-MMT reduced the cavity and pore diameters of the FPU foam. The compressive strength of the FPU/Na-MMT0.3 composite showed the highest increase of 27.75% when compared to the pristine FPU foam. Moreover, adding Na-MMT to FPU showed an improvement in the output voltage of the TENG for all nanocomposites, with the FPU/Na-MMT0.3 exhibiting the highest improvement of + 62.37% at a force of 4.8 N and a frequency of 5 Hz, compared to pristine FPU. The fabricated TENG device achieved a maximum power density of 0.0328 mW/cm2 at a load resistance of 20 MΩ with a contact area of 9×5 cm2. This device could power three commercial white light-emitting diodes (LEDs) connected in series. Additionally, the fabricated TENG device was employed to charge a 10 µF capacitor, reaching an energy storage of 1185.8 µJ. This demonstrates the device’s effectiveness in energy harvesting. Consequently, the prepared flexible FPU/Na-MMT nanocomposite foams are a promising material to use in TENG devices to power flexible electronic devices.

A Triboelectric Nanogenerator Based on Bamboo Leaf for Biomechanical Energy Harvesting and Self-Powered Touch Sensing

Recently, natural material-based triboelectric nanogenerators (TENGs) have increasingly attracted attention in academic circles. In this work, we have developed an innovative triboelectric nanogenerator (BL-TENG) utilizing bamboo leaves to capture biomechanical energy. Bamboo leaf, as a natural plant material, possesses a diverse array of applications due to its remarkable durability, which surpasses that of many other types of trees. Furthermore, bamboo leaf has the advantages of low cost, widely distributed, non-toxic and environmentally protected. The output power of the BL-TENG (size: 5 cm × 5 cm) is able to generate approximately 409.6 µW and the internal resistance of the BL-TENG is 40 MΩ. Furthermore, the BL-TENG can realize an open-circuit voltage (Voc) of 191 V and a short-circuit current (Isc) of 5 µA, respectively. The biomechanical energy harvesting effect of the BL-TENG device means that it can drive 18 commercial light-emitting diodes (LEDs) through the full-wave bridge rectifier. Furthermore, the BL-TENG can also serve as a self-powered touch sensor to reflect hand touch states. This study proposed a novel plant-based TENG device that can enhance the development of green TENG devices and self-powered sensing systems.

Enhancing the Output of Liquid-Solid Triboelectric Nanogenerators through Surface Roughness Optimization.

The advent of liquid-solid triboelectric nanogenerators (LS-TENGs) has ushered in a new era for harnessing and using energy derived from water. To date, extensive research has been conducted to enhance the output of LS-TENGs, thereby improving water utilization efficiency and facilitating their practical application. However, in contrast to intricate chemical treatment methods and specialized structures, a straightforward operational process and cost-effective materials are more conducive to the widespread adoption of LS-TENGs in practical applications. This work presents a novel method to enhance the output of LS-TENGs by increasing the liquid-solid contact area. The approach involves creating roughness on the solid surface through sandpaper grinding, which is simple in design and easy to operate and significantly reduces the cost of the experiment. The theory is applied to the solid triboelectric layer commonly used in the LS-TENG, demonstrating its universality and wide applicability to improve the output of the LS-TENG. The practical performance of the device is demonstrated by charging the capacitor and external load and driving the hygrometer and commercial 5 W LED light bulb, which can directly light up 300 commercial light-emitting diodes (LEDs) driven by a drop of water. This work provides a new method for the optimization of LS-TENGs and contributes to the wide application of LS-TENGs. This is a significant step forward in the field of energy harvesting and utilization.

Observation of piezoelectricity in a lead-free Cs2AgBiBr6 perovskite: a new entrant in the energy harvesting arena.

Halide perovskite materials have recently been recognised as powerful ferroelectric and piezoelectric materials with applications in the energy harvesting arena, but their experimental proof is very limited. We achieved strong intrinsic piezoelectricity in the lead-free inorganic double perovskite Cs2AgBiBr6 at room temperature and utilized it for mechanical energy harvesting, with a piezoelectric co-efficient (d33) of 12.7 pC N-1. Hysteresis loop and structural analyses offered further validation for the substantial ferroelectric features of the as-synthesised double perovskite. Density functional theory (DFT) calculations revealed the presence of anharmonic phonon soft modes in tetragonal Cs2AgBiBr6 due to dynamic instability, which resulted in piezoelectricity. Under an optimal pressure of ≈25 kPa, a Cs2AgBiBr6 thin film-based piezoelectric nanogenerator device delivered instantaneous output values of ≈45 V and ≈200 nA. The strain-sensitive responses of the device were also exemplified to identify specific body motions from the detected instantaneous output values. The energy obtained from the device is shown to be effective for capacitor charging and commercial light-emitting diode (LED) lighting. Our study provides significant insights into the dielectric behaviour of materials as well as piezo- and ferroelectric behaviours, which are crucial for the development of modern electronic and energy harvesting devices.

Improved Energy Harvesting Ability of Single-Layer Binary Fiber Nanocomposite Membrane for Multifunctional Wearable Hybrid Piezoelectric and Triboelectric Nanogenerator and Self-Powered Sensors.

While wearable self-powered electronic devices have shown promising improvements, substantial challenges persist in enhancing their electrical output and structural performance. In this work, a working mechanism involving simultaneous piezoelectric and triboelectric conversion within a monolayer-structured membrane is proposed. Single-layer binary fiber nanocomposite membranes (SBFNMs) (PVDF/CNTX@PAN/CNTX, DPCPCX) with two distinct interpenetrating nanocomposite fibers were created through co-electrospinning, incorporating multiwalled carbon nanotubes (CNTs) into polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN), respectively. The resulting membrane demonstrated an exceptional synergistic effect of piezoelectricity and triboelectricity along with a high machine-to-electric conversion capability. The addition of CNTs increased the PVDF β-phase and the PAN planar zigzag conformation. As a result, the DPCPC0.5-SBFNMs-based piezoelectric nanogenerator exhibited excellent electrical output (187 V, 8.0 μA, and 1.52 W m-2), maintaining an exceptionally high level of output voltage compared with other piezoelectric nanogenerators. It successfully illuminated 50 commercial light-emitting diodes simultaneously. The output voltage of DPCPC0.5-SBFNMs was 5.1 and 4.6 times higher than that of PAN or PVDF single-fiber membranes, respectively. Furthermore, the peak voltage of DPCPC0.5-SBFNMs exceeded that of co-electrospinning PVDF/CNT1.0@PAN (DPCP1.0) and PVDF@PAN/CNT1.0 (DPPC1.0) by 20 and 10 V, respectively. The piezoelectric sensor made of DPCPC0.5-SBFNMs accurately sensed human movement, ranging from tiny to large, and demonstrated utility as an alarm in medical treatment, fire fighting, and monitoring. Endogenous triboelectricity is proposed in SBFNM piezoelectric materials, enhancing electromechanical conversion and electrical output capacity, thereby promising a wide application potential in self-powered wearable electronic devices.

A pitched roof-like hybrid piezo/triboelectric nanogenerator with reliable supply capability for building a self-powered industrial monitoring system

As a result of increasingly stringent power supply requirements and diverse application scenarios, the development of hybrid nanogenerators that can combine multiple power generation modes has gradually become a hot research topic. In this work, the PR-HNG, a piezo/triboelectric hybrid nanogenerator based on a pitched roof structure, is proposed and is used efficiently to perform discrete mechanical energy harvesting. Using the flexible connection of its separated roof-like trigger mechanism, the PR-HNG operates through inertia under vibration conditions and achieves a satisfactory working state with very low mechanical loss. At 10 Hz, the instantaneous open-circuit voltage VOC and short-circuit current ISC of the PR-HNG can reach 800 V and 9.6 mA (1.60 A/m2), respectively, and no obvious attenuation occurs during high-intensity and long-term operation. After connection to a load via a rectifier bridge, the PR-HNG has a maximum power output of 575 μW/cm2 and can charge a 2 mF capacitor up to more than 2.5 V in only 30 s; these two performance parameters are better than the reported values for other similar types of HNG. In practical applications, this PR-HNG can easily drive more than 1440 commercial light-emitting diodes and can drive small electronic devices in real time. Therefore, the PR-HNG has been demonstrated to provide a credible and promising solution for fabrication of self-powered monitoring systems for use in industrial environments.

LED biasing scheme with thermal compensation for automotive industry applications

This work introduces a novel scheme for driving light-emitting diodes (LEDs) with thermal compensation. The primary objective of the system is to address the issue of emitted light intensity drift caused by temperature variations, with a particular focus on the automotive industry. The developed technique proposes an alternative approach to the traditional thermal approach, which primarily focuses on heat dissipation. In contrast, the presented strategy utilizes a temperature-dependent element, such as a thermistor, to generate a reference current that increases with temperature. The generated current is then amplified by a commercial integrated driver and employed to bias the LEDs. Consequently, the reduction in the emitted light intensity resulting from an increase in the internal temperature of the LED is counterbalanced by an elevation in the bias current. The luminous flux model developed for the proposed system predicts the attainment of stable light intensity across a wide temperature range. The proposed strategy has been applied to three commercial LEDs commonly employed in automotive signal lighting to produce red, yellow, and white light. Experimental results confirm a significant reduction in the thermal dependence of the luminous flux, with reduction factor of temperature dependence ranging between 3.7 and 14.2 for the least and most temperature-sensitive LED models analyzed, respectively.

New green garnet-type phosphor LuMgAl5SiO12:Ce3+ for filling cyan gap to achieve full-spectrum and high colour-rendering-index white light-emitting diodes

Phosphors with simple preparation, high luminous efficiency and excellent thermal stability are highly desirable for commercial white light-emitting diodes (W-LED). In the paper, a new garnet-type green phosphor LuMgAl5SiO12:Ce3+ (LMASO:Ce3+) has been successfully prepared by a high-temperature solid-state reaction. The crystal structure and photoluminescence properties were investigated in detail. X-ray diffraction and the Rietveld refinement demonstrated the crystal structure of LMASO belongs to cubic systems with an Ia 3¯ d (230) space group. The unit cell parameters of LMASO:0.08Ce3+ phosphor were found to be a = 11.90418 Å and V = 1686.935 Å3. LMASO:Ce3+ phosphors have two excitation bands with peaks at 340 and 436 nm, attributed to the 4f → 5d transition of Ce3+ ions. Under excitation at 436 nm, LMASO:0.08Ce3+ phosphor exhibits a broad and asymmetric emission band in the 450–700 nm range. Notably, a W-LED device was created by combining a 455 nm blue LED chip with the obtained green sample and the commercially available red CaAlSiN3:Eu3+ phosphor. The device emitted a bright warm white light with a low correlated color temperature of 3584 K and a high color rendering index of 96.0 at a drive current of 40 mA. The article indicates that LMASO:Ce3+ samples can serve as a potential green phosphor for W-LEDs, and offers a new strategy for designing efficient phosphors.

Large-scale efficient mid-wave infrared optoelectronics based on black phosphorus ink

The mid-wave infrared (MWIR), ranging from 2 to 5 micrometers, is of substantial interest for chemical sensing, imaging, and spectroscopy. Black phosphorus (bP)–based MWIR light emitters and detectors have been shown to outperform the state-of-the-art for commercial devices due to the low Auger recombination coefficient of bP. However, the scalability of these devices remains a challenge. Here, we report a bP ink formula that preserves the exceptional MWIR optoelectronic properties of bP to deposit centimeter-scale, uniform, and pinhole free films with a photoluminescence quantum yield higher than competing III-V and II-VI semiconductors with similar bandgaps at high excitation regime. As a proof of concept, we use bP ink as a “phosphor” on a red commercial light-emitting diode to demonstrate bright MWIR light emission. We also show that these films can be integrated into heterostructure device architectures with electron and hole selective contacts for direct-injected light emission and detection in MWIR.

Synthesis and photoluminescence properties of single-phase Sr3B14O24:RE3+ (RE = Ce, Tb, Sm, Eu) phosphors and glass for WLEDs, UV and NIR shielding

Commercial white light-emitting diodes (WLEDs) usually face problems such as lack of red emission, color difference caused by different degradation rates of multiphase phosphors and the poor thermal stability of the organic encapsulants. The development of new single-phase phosphors and glass can solve these problems well. Sr3B14O24:RE3+ (RE = Ce, Tb, Sm, Eu) phosphors and glass were synthesized by solid-phase method. The obtained Sr3B14O24:RE3+ (RE = Ce, Tb, Sm, Eu) samples showed multicolor emission including blue, green, orange and red, respectively. The optimal excitation wavelength of these samples was located in the blue or ultraviolet (UV) light regions, which were well matched with the blue-violet light chips to manufacture WLEDs. More interestingly, UV absorption was found in Sr3B14O24:Ce3+/4+ glass samples. The doping of dual-valence cerium ions could enhance the shielding performance in the light of inferences drawn from the UV-Vis absorption and transmission spectra of glass samples. By co-doping different concentrations of Cs+ ions in Sr3B14O24:Ce3+/4+ glass samples, the function of near infrared (NIR) shielding was also realized. As a new optical multifunctional material, rare earth doped Sr3B14O24 have great potential for application in WLEDs, UV and NIR shielding.

Enhancing quantum efficiency of Mn4+-doped fluoride phosphors through reverse doping strategy toward potential biological detection

Mn4+-doped fluoride red-emitting materials are renowned for their distinct characteristics, including fixed emission peaks and narrow spectral emission, rendering them highly favored in photoluminescent light-emitting diodes (LEDs). However, achieving ultra-high-concentration Mn4+ doping in fluoride phosphors is imperative to enhance quantum efficiency. Nevertheless, attaining such doping levels in metastable compound systems poses considerable challenges. In this study, we introduce an innovative reverse doping strategy, leading to the synthesis of Mn4+-doped cubic K2SiF6 phosphor (11.38 mol %) from hexagonal K2MnF6. Remarkably, this approach significantly improves the external quantum efficiency (EQE) to 66.7 % upon 450 nm excitation. Through systematic comparisons with conventional co-precipitation and ion exchange methods, our findings unequivocally demonstrate the superior efficacy of this approach in achieving high-concentration Mn4+ ion doping within relatively insoluble matrices. The successful application of our optimized phosphor enabled the fabrication of a red light-emitting diode (LED) that exhibits an exceptional photoelectric efficiency of 31.67 % at 350 mA, surpassing the performance of a commercial red LED chip. Furthermore, the stable red-light emission from the phosphor-converted LED (pc-LED) proves instrumental in rapid-response vascular imaging, showcasing the potential of our findings in advancing light sources for biological detection applications. This research provides valuable insights into enhancing red emission efficiency in slightly-soluble fluoride phosphors via novel synthetic strategy, unlocking possibilities for the development of highly efficient light sources in biological detection and imaging applications.

Smart-textile supercapacitor for wearable energy storage system

Textile based energy storage is becoming increasingly popular for smart-textile sensing application while being comfortable and relatively easy to integrate into clothing. In this study, textile fabric was structured in a mesh geometrical configuration by embroidery stitching technology, which provides high flexibility and stability in the fabrication of wearable supercapacitor devices. The output performance of the textile supercapacitor provides specific capacitance, energy density and power density 266.6 Fg−1, 37.027 Whkg−1 and 177 Wkg−1 for silver mesh fabric and 172 Fg−1, 24.583 Whkg−1 and 118.156 Wkg−1 for stainless steel mesh respectively as can be seen by the cyclic voltammogram (CV) curve of the supercapacitor at a scan rate of 10 mV/s. Silver mesh fabric supercapacitor is provided higher output performance as compare to stainless steel mesh fabric and presented capacitance retention stability at 95.4 % after 5000 cycles at a constant current of 0.25 mA. The fabricated textile supercapacitor is able to be charged up to 2.8 V of 3.0 s at constant current of 2.0 mA and able to be lighted up a commercial light-emitting diodes (LEDs). All experimental results indicate that supercapacitors constructed with silver mesh fabric and graphene oxide/manganese dioxide (G-MnO2)/carbon black have the potential to serve as electrode materials and flexible substrate for flexible textile-based supercapacitors.

A drum-like piezoelectric rotational energy harvester via magnetic beating

In this Letter, an indirectly excited approach of introducing an air-filled separation chamber is proposed to develop a drum-like piezoelectric rotational energy harvester (DL-PREH) via magnetic beating. The harvester delivers the external excitation to the piezoelectric transducer via the intermediate air chamber, and the electric output of transducer is induced by the air pressure inside the chamber. Thus, a high reliability can be guaranteed for the harvester under an unexpected excessive impact due to the air-filled separation zone. Moreover, the harvester can easily implement a resonant frequency tuning by altering the drum height to improve the rotation speed adaptability. Its potential applications as a sustainable power source to charge different capacitors and power commercial light-emitting diodes (LEDs) are demonstrated experimentally. The fabricated DL-PREH device can achieve a maximum output power of 10.63 mW with a drum height of 6 mm at the matching resistance of 24 kΩ. Also, it can light up at least 100 blue commercial LEDs in parallel. The designed harvester exhibits its good power generation capability and resonance frequency tunability.