Low Power Density Research Articles

Cross-sectional profile of photocarrier mobility in thin-film solar cells via multimolecular recombination and charge extraction by linearly increasing voltage (cs-p-CELIV)

The ability to spatially resolve the carrier mobility profile along the cross section of micrometer-thin solar cells is vital, both for fundamental studies in photovoltaics and as quality control for reproducibly obtaining high conversion efficiencies in commercial solar cell modules. Presently, no technique capable of such an endeavor is available to the best of our knowledge. Here, we introduce a novel method capable of profiling the carrier mobility along the z axis in thin-film photovoltaics. Our setup is based on the integration of photogenerated charge extraction by linearly increasing voltage (p-CELIV) with a scanning confocal optical microscope (SCOM) toward a confocal and cross-sectional p-CELIV (cs-p-CELIV) system. As monomolecular recombination of excess carriers is the most frequent radiative pathway for electrons and holes in solar cells at low power density of illumination, while multimolecular recombination dominates at high power, enhanced multimolecular recombination occurs at the SCOM focal plane. Thus, the cs-p-CELIV signal provides enhanced information on the mobility of all of the cross-sectional layers except the focal plane. By scanning the focal plane along the z axis, the mobility profile can be derived. To demonstrate our technique, we use it to investigate the carrier mobility in three hydrogenated amorphous silicon (a-Si:H) solar cells. The mobility profiles obtained by cs-p-CELIV correlate well with well-known depletion layer effects and the H content profile in a-Si:H, which is measured independently. Our findings are in excellent agreement with models suggesting a critical role of Si–H bonding in locally determining the carrier mobility in a-Si:H.

Pseudocapacitance behavior enables efficient and stable electrochemical energy conversion and storage in glucose/air enzymatic biofuel cells

Constructing an integrated system with high-efficiency and stable energy conversion and storage (ECS) is of great significance but remains challenges. Herein, we report a biodevice consisting of a bioanode of tetrathiafulvalene/glucose oxidase (TTF/GOx) immobilized on asphalt-derived porous carbon (APC) for catalyzing glucose oxidation and a biocathode of 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonate)/bilirubin oxidase (ABTS/BOD) immobilized on APC for catalyzing oxygen reduction, to achieve ECS with high-efficiency and excellent stability. The redox mediators, TTF and ABTS, used at the bioanode and biocathode, respectively, simultaneously mediate electron transfer to release electric current on discharging and serve as pseudocapacitors to achieve charge storage at open-circuit conditions, enabling high power density and self-charge capability. The biodevice of the above configuration delivers a peak power output of 5.01 mW cm−2 in the pulse discharge mode with cell voltage remaining 93.7 % of its initial value after 100 pulse discharge/self-charge cycles. This work provides a highly efficient solution to address the low power density and poor stability of the conventional enzymatic biofuel cells, showing great implications for small, implantable and wearable electronics.

V2O5 coral microspheres: High performance electrode material for Li-ion supercapacitor

Energy storage devices forms lifeline for most modern devices. The short life cycle and lower power density of batteries has prompted development of supercapacitors as potential alternatives. Li-ion supercapacitors, is an emerging class of energy storage devices. Natural abundance and availability of variable oxidation states make V2O5 an attractive electrode material. Here, we report synthesis of coral microspheres of V2O5 using low temperature solvothermal technique, as electrode material for Li-ion supercapacitor. The annealing temperature plays a cucial role in formation of microspherical aggregates, dictates their surface area and hence the energy storage performance. Samples annealed at 400 °C showed specific capacitance of ∼360 F/g at current density of 0.5 A/g. Our studies suggest that V2O5 based nanostructures holds significant potential for development of hybrid Li-ion supercapacitors.

Modified Wood Fibers Spontaneously Harvest Electricity from Moisture.

With the rapid development of modern society, our demand for energy is increasing. And the extensive use of fossil energy has triggered a series of problems such as an energy crisis and environmental pollution. A moisture-enabled electric generator (MEG) is a new type of energy conversion method, which can directly convert the ubiquitous moisture in the air into electrical energy equipment. It has attracted great interest for its renewable and environmentally friendly qualities. At present, most MEGs still have low power density, strong dependence on high humidity, and high cost. Herein, we report the development of a high-efficiency MEG based on a lignocellulosic fiber frame with high-power-density, all-weather, and low-cost characteristics using a simple strategy that optimizes the charge transport channel and ion concentration difference. The MEG devices we manufactured can generate the open-circuit voltage of 0.73 V and the short-circuit current of 360 μA, and the voltage can still reach 0.6 V at less than 30% humidity. It is possible to drive commercial electronic devices such as light-emitting diodes, electronic displays, and electronic calculators by simply connecting several electric generators in series. Biomass-based moisture-enabled electric generation has a low cost, is easy to integrate on a large scale, and is green and pollution-free, providing clean energy for low-humidity or high-electricity-cost areas.

Triplet Upconversion under Ambient Conditions Enables Digital Light Processing 3D Printing.

The rapid photochemical conversion of materials from liquid to solid (i.e., curing) has enabled the fabrication of modern plastics used in microelectronics, dentistry, and medicine. However, industrialized photocurables remain restricted to unimolecular bond homolysis reactions (Type I photoinitiations) that are driven by high-energy UV light. This narrow mechanistic scope both challenges the production of high-resolution objects and restricts the materials that can be produced using emergent manufacturing technologies (e.g., 3D printing). Herein we develop a photosystem based on triplet-triplet annihilation upconversion (TTA-UC) that efficiently drives a Type I photocuring process using green light at low power density (<10 mW/cm2) and in the presence of ambient oxygen. This system also exhibits a superlinear dependence of its cure depth on the light exposure intensity, which enhances spatial resolution. This enables for the first-time integration of TTA-UC in an inexpensive, rapid, and high-resolution manufacturing process, digital light processing (DLP) 3D printing. Moreover, relative to traditional Type I and Type II (photoredox) strategies, the present TTA-UC photoinitiation method results in improved cure depth confinement and resin shelf stability. This report provides a user-friendly avenue to utilize TTA-UC in ambient photochemical processes and paves the way toward fabrication of next-generation plastics with improved geometric precision and functionality.

Non-precious HfO2 nanoparticle as an alternative cathode catalyst for microbial fuel cell applications

This study evaluated hafnium oxide (HfO2) as a cathode catalyst material in air-cathode single-chamber microbial fuel cells (SCMFCs). Various HfO2 crystalline phases, synthesized via a precipitation method under specific temperature conditions, were examined for electrochemical performance in MFCs, including voltage, power generation, cyclic voltammetry, and impedance spectroscopy. The MFC-600 °C variant outperformance MFC-500 °C and MFC-700 °C yielding power density of 1152 ± 9 mW m−2 and voltage 284 ± 8 mV. In a double loading (DL) configuration (1 mg cm−2), MFC-600 °C exhibited higher power density than single loading and triple loading. The MFC-600 °C DL electrode showed up to 57.3% of the performance of the traditional Pt/C cathode (2009 ± 12 mW m−2). On the other hand, when considering catalyst loading, the 10% Pt/C (0.5 mg cm−1) had a lower power density than the HfO2 600 °C DL (1 mg cm−1): 4.018 mW m−2 g−1 vs. 11.52 mW m−2 g−1. These findings highlight the promising viability of the HfO2 cathode as an economically advantageous catalyst material for MFCs, potentially paving the way for commercialization.

Boosting the Output of Liquid–Solid Triboelectric Nanogenerator by an External Charge‐Pumping Strategy

AbstractIn recent years, liquid–solid triboelectric nanogenerator (LSTENG) has attracted great attention. However, its low average power density and long charging time limit the practical application of this technique. Here, for the first time, a liquid–solid triboelectric nanogenerator combined with external charge‐pumping method (ECP‐LSTENG) is proposed. Compared to traditional LSTENGs, a charge storage capacitor is added in this ECP‐LSTENG to store the output charges from the pumping generator. Then, a charge extraction capacitor is formed by the spreading and shrinking processes of falling droplet, while the charging and discharging process between charge storage and extraction capacitors can generate displacement current output for external circuit. Meanwhile, it is found that a special charged droplets adhesion phenomenon happens at the liquid–solid interface, which seriously hinders the continuous output of ECP‐LSTENG. To overcome this limitation, a special coaxial deceleration commutation component is designed to ensure continuous output of the ECP‐LSTENG. Finally, the peak power density of a droplet (50 µL) reaches 231.8 W m−2, surpassing the highest research record to date by 1.43 times. This ECP‐LSTENG provides a different approach for the future development of large‐scale integrated raindrop generators for efficient raindrop energy harvesting.

Influence of ionomer concentration and membrane thickness on membrane electrode assembly in alkaline fuel cell performance

AbstractThe alkaline fuel cell is subject to extensive research owing to its fast kinetic response relative to acidic media. However, the efficiency of the catalytic layer at the electrodes depends on the amount and distribution of ionomers present there. It is crucial to have the right ionomer concentration to have the best cell performance. Additionally, the membrane thickness is a significant parameter that affects the system performance in alkaline fuel cells. This research studies the best alkaline fuel cell performance using the membrane electrode assembly preparation parameters. The prepared membrane electrode assembly consists of catalyst layers containing Fumion, a commercial anion exchange ionomer, as a binding agent, sandwiched a Fumasep, a well‐known commercial anion exchange membrane. This work elucidates the single‐cell alkaline fuel cell performance by quantifying the influence of Fumion concentrations (~20–60 wt.%) within the catalytic layer and Fumasep thicknesses (30, 75 and 130 μm). The best concentration of Fumion was found to be 50 wt.%, culminating in the maximum peak power density of 67 mW cm−2 achieved by the FAA‐3‐PK‐75. Meanwhile, FAA‐3‐PK‐130 exhibited the highest open‐circuit potential with lowest power density at 53 mW cm−2. These findings may serve as a valuable guide for membrane electrode assembly preparation in alkaline fuel cells.

Crystal Violet (CV) Biodegradation Study in a Dual-Chamber Fungal Microbial Fuel Cell with Trichoderma harzianum

In the present study, CV dye, known as a recalcitrant dye, was tested for bioremediation via Trichoderma harzianum in a dual-chambered MFC for the first time. Two types of carbon clothes, KIP and CSV from the Dacarb company (France), were tested as electrodes and supported for fungi growth. We first observed that 52% and 55% of the CV were removed by the MFC using KIP and CSV anodes, respectively. The incomplete removal of VC was explained by the relative toxicity of VC to T. harzianum and correlated with IC50 determined as 0.97 ± 0.28 mg L−1 at 25 °C. Furthermore, the MFC working with the KIP electrode was more efficient with a higher maximum power density of 1096 mW m−3 and was only 14.1 mW m−3 for CSV. The MFC experiments conducted on KIP without the T. harzianum biofilm exhibited significantly lower potential and power density values, which proves the electrocatalytic effect of this fungus. These results provide new insight into the development of an effective MFC system capable of direct energy generation and, at the same time, promoting the bioremediation of the persistent CV pollutant.

Experimental and numerical investigation of methane combustion in a HCCI engine under enriched oxygen conditions

The challenge in the energy transition lies in the intermittent nature of renewable energy, requiring the development of effective storage methods. E-fuels are considered a promising solution, with potential applications to Homogeneous Charge Compression Ignition (HCCI) engines known for their high thermal efficiency and low nitrogen oxide emissions. However, HCCI engines face limitations such as low power density and a narrow operating range. To overcome these issues, oxygen-enriched combustion is proposed, aiming at enhancing the mixture reactivity and expanding the operating range by decreasing the intake temperature. As the potential of the expansion of the operating range has never been investigated, we performed an experimental campaign using a methane-fuelled HCCI engine at variable oxygen fractions in the oxidizer. To further elucidate the effects of oxy-fuel combustion, we also performed a kinetic analysis of the reactions driving the combustion behaviour. It has been experimentally found that increasing the oxygen content in the mixture, up to 90%, has a significant potential to decrease the needed intake temperature (up to 70 °C) of the charge to keep the Maximum Pressure Rise Rate (MPRR) below the safety threshold of 8 bar/CAD. Despite the notable IMEP increase achieved, operating the engine at high oxygen content presents significant technical challenges. Therefore, to make HCCI engines competitive with other combustion modes, it is essential to combine oxygen enrichment with additional power density enhancement techniques. The kinetic analysis has highlighted that the mixture is less sensitive to intake temperature changes at higher oxygen percentages (above 50%) and that the rates of the main reactions involved in methane and OH consumption are highly enhanced by oxygen addition.

A novel high-efficiency integrated system combining a thermally regenerative electrochemical cycle and a flow battery

A thermally regenerative electrochemical cycle (TREC) harnesses the temperature effect of electrode potential to achieve efficient heat to electricity conversion but suffers from low power density.

Unlocking the potential: Ultra-wideband

The demand for wireless wideband communications is rising as a result of the need to accommodate more users and deliver more data at faster data rates. Ultra-wideband (UWB) technology, which uses very brief pulses on the order of nanoseconds to cover a very large frequency spectrum, may be able to tackle this problem. UWB is a wireless technology with several potential applications that was created to transmit data at extremely high speeds over very short distances at very low power densities. This paper presents the UWB technology as it currently exists and its potential uses. The question of how to employ this technology without interfering with the current means of communication is also investigated. Comparisons with other wireless technologies highlight UWB's superiority in terms of accuracy, power consumption, and cost-effectiveness. The paper also explores modulation techniques and deployment scenarios, showcasing UWB's capability to revolutionize short-range communication networks and seamlessly integrate with existing wireless infrastructures.

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

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

Adaptive nanotube networks enabling omnidirectionally deformable electro-driven liquid crystal elastomers towards artificial muscles.

Artificial muscles that can convert electrical energy into mechanical energy promise broad scientific and technological applications. However, existing electro-driven artificial muscles have been plagued with problems that hinder their practical applications: large electro-mechanical attenuation during deformation, high-driving voltages, small actuation strain, and low power density. Here, we design and create novel electro-thermal-driven artificial muscles rationally composited by hierarchically structured carbon nanotube (HS-CNT) networks and liquid crystal elastomers (LCEs), which possess adaptive sandwiched nanotube networks with angulated-scissor-like microstructures, thus effectively addressing above problems. These HS-CNT/LCE artificial muscles demonstrate not only large strain (>40%), but also remarkable conductive robustness (R/R0 < 1.03 under actuation), excellent Joule heating efficiency (≈ 233 °C at 4 V), and high load-bearing capacity (R/R0 < 1.15 at 4000 times its weight loaded). In addition, our artificial muscles exhibit real-muscle-like morphing intelligence that enables preventing mechanical damage in response to excessively heavyweight loading. These high-performance artificial muscles uniquely combining omnidirectional stretchability, robust electrothermal actuation, low driving voltage, and powerful mechanical output would exert significant technological impacts on engineering applications such as soft robotics and wearable flexible electronics.

A robust tubular solid oxide fuel cell through bifunctional praseodymium oxide nanocatalyst infiltration

Due to inherent merits such as rapid start-up, easy sealing, and good thermal cycling resistance, tubular solid oxide fuel cell (SOFC) is becoming a promising alternative device for clean and efficient energy conversion; yet the lower power density is a challenging problem when compared to planar SOFC. In this study, an asymmetric infiltration of Pr6O11 nanocatalyst, a bi-functional catalyst, is innovatively proposed to enhance the electrochemical performance and prolong the cell lifespan. First, a suitable anode functional layer (AFL) based on the Ni-YSZ (yttria stabilized zirconia) anode is presented. The additional AFL results in a significantly enhanced peak power density (PPD) of 1259 mWcm−2 at 800 °C, which is 66 % higher than that of the primitive cell (756 mWcm−2). Subsequently, a new approach of asymmetric infiltration is devised in one step during the cell manufacturing procedure to simultaneously modify the anode and cathode-electrolyte interface to boost cell output power. Consequently, the nanostructure-engineered tubular cell exhibits outstanding peak power density of 1592 mWcm−2 at 800 °C, that is more than twice that of the blank cell, outperforms the majority of the Ni-YSZ supported tubular cells. Furthermore, the robust tubular cell runs on hydrogen fuels with excellent stability over more than 2000 h at a constant current density of ∼300 mAcm−2. The exceptional performance and endurance can be attributed to the rational cell design, which holds great potential for the commercialization of tubular SOFC.

Study of spatially confined copper plasma by probe beam deflection technique

In the last decade, laser induced plasma (LIP) has emerged as one of the most promising techniques for various applications. It is now commonly investigated using various expensive techniques. Probe beam deflection (PBD) is an inexpensive technique generally utilized to characterize the shock wave. In this work, the copper laser-induced plasma plume and shock wave are both investigated using PBD technique. The plasma is generated at atmospheric pressure using Nd:YAG laser at a low laser power density (0.8 GW/cm2). The contribution of the plasma plume components to the PBD signal is clarified in space and time. The spatial confinement effect by a metallic disk is also investigated. It approves the physical mechanisms responsible for the deflection signal. As well, the spatial distribution of the weak shock wave velocity is considered.

Influence of NIR-laser radiation on the underwater arc welding process with flux-cored wire

The combination of laser radiation and electric arc as hybrid welding is used successfully in industry. In the underwater area, this technology is currently being researched but is not yet part of the industry. This paper demonstrates laser-stabilized arc welding with flux-cored electrode for underwater applications where the laser power density of the laser radiation does not result in a deep penetration welding effect. Steel samples (S235-JR) with a thickness of 10 mm were examined as bead-on-plate welds with a laser power density of 0.7-2.8 x 104 W/cm² at a wavelength of 1030 nm. The addition of laser radiation at low laser power density stabilizes the arc and produces a homogeneous weld seam. The process behavior and stability are characterized by measuring the current and voltage signals and analyzed regarding the laser beam and current source parameters. The metallographic analyses are used to compare the weld seam geometry and the microstructure properties.

A Dual-Layer Receiver With Low Interlayer Voltage Stress and High Power Density for EVs Wireless Charging System

A Dual-Layer Receiver With Low Interlayer Voltage Stress and High Power Density for EVs Wireless Charging System

Investigation of non-precious metal cathode catalysts for direct borohydride fuel cells.

Borohydride crossover in anion exchange membrane (AEM) based direct borohydride fuel cells (DBFCs) impairs their performance and induces cathode catalyst poisoning. This study evaluates three non-precious metal catalysts, namely LaMn0.5Co0.5O3 (LMCO) perovskite, MnCo2O4 (MCS) spinel, and Fe-N-C, for their application as cathode catalysts in DBFCs. The rotating disk electrode (RDE) testing shows significant borohydride tolerance of MCS. Moreover, MCS has exhibited exceptional stability in accelerated durability tests (ADTs), with a minimal reduction of 10 mV in half-wave potential. DFT calculations further reveal that these catalysts predominantly adsorb over , unlike commercial Pt/C which preferentially adsorbs . In DBFCs, MCS can deliver a peak power density of 1.5 W cm-2, and a 3% voltage loss after a 5 hours durability test. In contrast, LMCO and Fe-N-C have exhibited significantly lower peak power density and stability. The analysis of the TEM, XRD, and XPS results before and after the single-cell stability tests suggests that the diminished stability of LMCO and Fe-N-C catalysts is due to catalyst detachment from carbon supports, resulting from the nanoparticle aggregation during the high-temperature preparation process. Such findings suggest that MCS can effectively mitigate the fuel crossover challenge inherent in DBFCs, thus enhancing its viability for practical application.

Enhanced band-tuning and quality of Ni-doped Ga2O3 films via low-power RF magnetron sputtering

The proposed mechanism for the conductivity and band tuning in Ni-doped Ga2O3 films depends on the presence of oxygen vacancies and Ni ions. The Ni-doped Ga2O3 films were prepared using an extremely low power density of 0.18–0.36 W cm−2.