Commercial Light-emitting Diodes Research Articles

Dual-Functional Carbon Dot Films: Blue-Light Filtration and Cyan-Light Conversion for Healthier White Light-Emitting Diodes.

Blue light emitted by commercial white light-emitting diodes (WLEDs) in the 440-470 nm range poses ocular health risks with prolonged exposure. Effective filtration is crucial for health-conscious lighting, but traditional filters often cause color distortion by completely removing blue emission. In this study, we address this challenge by synthesizing carbon dots (CDs) with strong absorption at 460 nm and bright cyan emission at 485 nm, featuring a photoluminescence quantum yield of 65% and a narrow full width at half-maximum of 30 nm. When embedded in a poly(vinyl alcohol) (PVA) matrix, the CDs@PVA films effectively filter UV-to-blue light, reducing the blue-light ratio from 27.2% to 2.7%. At the same time, the cyan emission preserves the white light's spectral composition, achieving a color rendering index of 83 ± 5. This dual functionality demonstrates the potential of CDs to enable safer WLEDs that improve both ocular health and lighting quality.

Comparison spectral analysis and photometric parameters for different indoor and outdoor LEDs lighting

Light emitting diode (LED) lighting have gained in popularity owing to the advantages offered by them over incandescent lamps with respect to energy efficiency, strong robustness, operation life, and steadiness with time, making them suitable for a wide range of applications like residential and commercial lighting. In this work, the luminous flux and thermal stabilization time, color parameters, and spectral mismatch factors and their uncertainties have been measured and estimated for some indoor and outdoor commercial LED lamps of three different brands with nominal powers of 3, 9, and 36 watts. These lamps were classified into indoor-1, indoor-2, indoor-3, and outdoor LED lamps in order to enable the present analysis. The measurement methodology included a sophisticated luminous flux system using a 2.5-meter integrating sphere at the National Institute of Standards, NIS, equipped with the NIS photometer LMT U1000 and a series of NIS luminous flux secondary standard lamps calibrated at the National Physical Laboratory, NPL, in England. This is important for making proper, accurate measurements of the total luminous flux emitted by different LED lamps. In addition, an NIS Spectroradiometer (Ocean Optics HR 2000) and a photometric bench were used in order to measure the spectral power distribution of the lamps, by means of which we had the possibility to calculate the spectral mismatch correction factor quantify the color parameters and estimate the associated measurement uncertainties. The comprehensive approach in our study involves assessing luminous flux, thermal stabilization time, spectral mismatch correction factors, and chromaticity color coordinates, all in comparison to established standards provided by NIS Secondary Standard Lamps. This paper demonstrates that the obtained spectral mismatch correction factors and chromaticity color coordinates with their uncertainties can be used as basic corrections to luminous flux and color measurements. By doing this, the accuracy and dependability of these kinds of measurements are significantly improved, increasing the knowledge about the performance of LED lamps.

Nickel-Cobalt Layered Double Hydroxide Nanosheet-Decorated 3D Interconnected Porous Ni/SiC Skeleton for Supercapacitor.

In this study, a three-dimensional (3D) interconnected porous Ni/SiC skeleton (3D Ni/SiC) was synthesized by binder-free hydrogen bubble template-assisted electrodeposition in an electrolyte containing Ni2+ ions and SiC nanopowders. This 3D Ni/SiC skeleton served as a substrate for directly synthesizing nickel-cobalt layered double hydroxide (LDH) nanosheets via electrodeposition, allowing the formation of a nickel-cobalt LDH nanosheet-decorated 3D Ni/SiC skeleton (NiCo@3D Ni/SiC). The multiscale hierarchical structure of NiCo@3D Ni/SiC was attributed to the synergistic interaction between the pseudocapacitor (3D Ni skeleton and Ni-Co LDH) and electrochemical double-layer capacitor (SiC nanopowders). It provided a large specific surface area to expose numerous active Ni and Co sites for Faradaic redox reactions, resulting in an enhanced pseudocapacitance. The as-fabricated NiCo@3D Ni/SiC structure demonstrated excellent rate capability with a high areal capacitance of 1565 mF cm-2 at a current density of 1 mA cm-2. Additionally, symmetrical supercapacitor devices based on this structure successfully powered commercial light-emitting diodes, indicating the potential of as-fabricated NiCo@3D Ni/SiC in practical energy storage applications.

Flexible Triboelectric Nanogenerators Based on Cadmium Metal-Organic Framework/Eethyl Cellulose Composites as Energy Harvesters for Selective Photoinduced Bromination Reaction.

The fabrication of self-driven systems with flexibility and tunable output for organic photoinduction is highly desirable but challenging. In this study, a 3D cadmium metal-organic framework (Cd-MOF) is synthesized and used as a filler for ethyl cellulose (EC) to create mechanically durable and flexible Cd-MOF@EC composite films. Due to its well-established platform with periodically precise structure nature, the outputs of Cd-MOF-based TENG are much higher than those of ligand-based TENGs. Furthermore, composite films with different doping ratios of Cd-MOF are employed to assemble Cd-MOF@EC-based triboelectric nanogenerators (TENGs). The results reveal that a doping ratio of 10 wt.% Cd-MOF in Cd-MOF@EC provides the highest TENG output. Subsequently, a flexible 10 wt.% Cd-MOF@EC-based TENG (FCEC-TENG), working in the contact-separation model, is constructed to harvest mechanical energy from the human body, demonstrating excellent output performance and stability. The energy harvested from FCEC-TENG can directly illuminate 14 commercial white light-emitting diodes (LEDs), providing visible light for the photoinduction of the bromination reaction, and generating bromide with good yield and tolerance. This study presents an effective method for constructing flexible MOF-based TENG for self-powered photoinduced organic transformation systems.

Stretchable Micro-Supercapacitors Based on Laser Directly Patterned Graphene/Liquid Metal

Herein, we fabricate highly deformable micro-supercapacitors (MSCs) based on gallium indium liquid metal (EGaIn) current collectors with integrated graphene. The well-defined interdigitated electrode patterning with controlled gap was successfully realized by using laser ablation technique due to strong laser absorption of graphene and EGaIn. By carefully controlling the gap size between adjacent interdigitated electrodes and the mass loading of graphene, we achieved high areal capacitance (1336 µF/cm2) with reliable rate performance. In addition, due to the intrinsic liquid properties of the EGaIn current collector, the energy storage performance of the MSC maintained 90% of its original areal capacitance even after repeated folding and 20% stretching (1000 cycles). Finally, we successfully integrated the deformable MSC with a commercial light-emitting diode to demonstrate the feasibility of MSC as a deformable power source. The fabricated MSCs operated stably under various mechanical deformations, including stretching, folding, twisting, and wrinkling.

Conditions for thermally stable color characteristics of trichromatic white light-emitting diodes

We present a method to stabilize color characteristics from a trichromatic white light-emitting diode (LED) consisting of red, green, and blue (RGB) LEDs under varying ambient temperatures. Through colorimetric analyses, it was found that the trichromatic white LED could maintain its chromaticity coordinate by adjusting the light output power (LOP) of green and red LEDs as the temperature varied. Moreover, the correlated color temperature (CCT) could be invariant to the external temperature change by controlling only the LOP of a red LED. Using the developed mathematical model and temperature-dependent spectral data of commercial RGB LED samples, we determined the power ratios between RGB LEDs needed to achieve thermally stable color coordinates or CCT as the heat sink temperature varied from 20 to 100 °C. When operating under thermally stable CCT conditions, the chromaticity coordinate of the trichromatic LED moved along the iso-CCT line with only a minor color deviation as the temperature increased to 100 °C. The presented approach requires adjusting the power of only one LED to achieve thermally stable CCT operation in a trichromatic white LED, which is expected to simplify LED control circuits significantly.

Highly stretchable carbon-based triboelectric nanogenerator textiles woven using coaxial fibres via direct ink writing

In recent years, triboelectric nanogenerators have seen great progress in the Internet of Things, wearable electronics, virtual reality and artificial intelligence technologies. However, current triboelectric nanogenerator devices generally face challenges of complex preparation processes and structures, hindering their application in large-area wearable textiles. In this study, we develop highly stretchable triboelectric fibres using direct ink writing as building blocks for further woven textiles. This consists of a conductive core and insulating sheath, namely composites of multi-wall carbon nanotube and fluorinated ethylene propylene particles, both doped in silicone rubber. The fibre enjoys outstanding electrical performance, as well as excellent mechanical stretchability. Particularly, a single-centimetre-long fibre, upon slight patting, can surprisingly produce an open-circuit voltage of 8 V, a short-circuit current of 110 nA and 2.5 nC short-circuit transferred charges, or equivalent lighting of four to five commercial light-emitting diodes alone, greatly outperforming current wearable devices. These fibres also can endure an extraordinary strain of up to ∼874 %. The fibres are then woven into wearable gloves and socks using traditional weaving techniques, which can realise motion pattern identification and recognition with classification accuracy as high as ∼96 % using convolutional neural networks. This creates application prospects in wearable electronics, providing a scalable and affordable method for weaving daily wearable textiles and favouring large-area, wearable, self-powered sensors and artificial intelligence technologies.

Revealing multiphase coexistence of R-O-T phases in BaTiO3-CaTiO3-BaSnO3 electroceramics for energy harvesting and storage response with piezo actuation

The (Ba1-xCax)(SnyTi1-y)O3 piezoelectric ceramics (where x=0.016, y=0.024; x=0.032, y=0.048; x=0.048, y=0.072; x=0.064, y=0.096; x=0.08, y=0.12) were designed by conventional solid state reaction method. The crystal structure for the composition of x=0.064 and y=0.096 (abbreviated as BCST-4) possesses the coexistence of non-centrosymmetric rhombohedral-orthorhombic-tetragonal (R-O-T) tri-lattice symmetries at room temperature, as demonstrated by the structural Rietveld refinement, Raman analysis, and temperature dependence of dielectric study. Because of the R-O-T multiphase coexistence, BCST-4 possesses a superior electromechanical and piezoelectric property viz. kp ∼ 0.45, strain ∼ 0.100 %, d33* ∼ 649 pm/V, and an improved d33 ∼ 452 pC/N, which is comparable to commercially available soft PZT ceramics (d33 ⁓ 370 pC/N). For BCST-4 ceramics, an exceptional electrostriction coefficient Q33 ∼ 0.0434 m4/C2 value was attained. The intrinsic piezo-actuation DC strain was observed to be 130 microstrain (με) and 188 με with ε33 and ε31 modes respectively. The BCST-4 ceramic exhibits a maximum output power of 1.03 mW, a power density of 13.5 µW/mm3, a maximum output current of 88 µA, and an open circuit voltage Vpp of 28 V which successfully glowed ‘SPPU’ panel having 40 red commercial light-emitting diodes (LEDs). The energy storage study reveals that BCST-4 ceramics exhibit a maximum energy storage density (Wrec) of 165.87 mJ/cm3 with efficiency (ƞ) 68.00 %. Therefore, the improvement in electrostriction coefficient, piezoelectric charge coefficient, and energy storage response indicates that BCST-4 ceramic has the potential for actuator, energy harvesting, and energy storage applications.

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.

Strategically Developed Strong Red‐Emitting Oxyfluoride Nanophosphors for Next‐Generation Lighting Applications

AbstractRed‐emitting nanophosphors have a multirole in improvising the next‐generation bulk/micro/nano‐level lighting devices, particularly in refining white light quality and device performance. Nonetheless, it is difficult to synthesize nanosized phosphors with good yield and paralleled high absorption efficiency both in UV and blue regions, which is critical for modern lighting. Herein, new Mg14Ge4.99+σO24‐x+δFx: Mn4+ red nanoparticles with sizes below 100 nm are designed to improve not only the luminescence but also the blue light absorption. This approach has validated the applicability of red‐emitting nanophosphors into flexible UV and blue nitride nanowire light‐emitting‐diodes (LEDs), and commercial bulk LEDs, for the first time, with boosted intensity and color superiority for a variety of lighting utilizations. For these phosphor LEDs (pc‐LEDs), optimized red nanophosphor with an external quantum efficiency of ≈44.5%, color purity of ≈100%, and thermal stability of ≈72% at 150 °C is used. The optimized nanophosphor is combined with a flexible UV‐AlGaN/GaN nanowire LED and a blue‐InGaN/GaN‐LED. The resultant devices show promising red electroluminescence without any degradation at elevated currents. Finally, several unfamiliar LED packaging is designed with yellow and red phosphors implemented on 2 sets of double LED units to reach CRI > 85. The re‐premeditated LED packages are useful for high‐definition lighting.

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.