More Like this

1. A Review on Electrospun Luminescent Nanofibers: Photoluminescence Characteristics and Potential Applications

   https://doi.org/10.2174/1573413715666190112121113  

   George, Gibin; Luo, Zhiping (April 2020, Current Nanoscience)

   Background: Photoluminescent materials have been used for diverse applications in thefields of science and engineering, such as optical storage, biological labeling, noninvasive imaging,solid-state lasers, light-emitting diodes, theranostics/theragnostics, up-conversion lasers, solar cells,spectrum modifiers, photodynamic therapy remote controllers, optical waveguide amplifiers andtemperature sensors. Nanosized luminescent materials could be ideal candidates in these applications.Objective: This review is to present a brief overview of photoluminescent nanofibers obtainedthrough electrospinning and their emission characteristics.Methods: To prepare bulk-scale nanosized materials efficiently and cost-effectively, electrospinningis a widely used technique. By the electrospinning method, a sufficiently high direct-current voltageis applied to a polymer solution or melt; and at a certain critical point when the electrostatic forceovercomes the surface tension, the droplet is stretched to form nanofibers. Polymer solutions or meltswith a high degree of molecular cohesion due to intermolecular interactions are the feedstock. Subsequentcalcination in air or specific gas may be required to remove the organic elements to obtainthe desired composition.Results: The luminescent nanofibers are classified based on the composition, structure, and synthesismaterial. The photoluminescent emission characteristics of the nanofibers reveal intriguing featuressuch as polarized emission, energy transfer, fluorescent quenching, and sensing. An overview of theprocess, controlling parameters and techniques associated with electrospinning of organic, inorganicand composite nanofibers are discussed in detail. The scope and potential applications of these luminescentfibers also conversed.Conclusion: The electrospinning process is a matured technique to produce nanofibers on a largescale. Organic nanofibers have exhibited superior fluorescent emissions for waveguides, LEDs andlasing devices, and inorganic nanofibers for high-end sensors, scintillators, and catalysts. Multifunctionalitiescan be achieved for photovoltaics, sensing, drug delivery, magnetism, catalysis, andso on. The potential of these nanofibers can be extended but not limited to smart clothing, tissueengineering, energy harvesting, energy storage, communication, safe data storage, etc. and it isanticipated that in the near future, luminescent nanofibers will find many more applications in diversescientific disciplines. 

   more » « less
2. A Four Port Isolated PV-Based EV Charger that Supports level-2 and DC Charging

   https://doi.org/10.1109/ECCE50734.2022.9947535  

   Tamasas Elrais, Mohamed; Rezaii, Reza; Ghosh, Sumana; Batarseh, Issa (October 2022, 2022 IEEE Energy Conversion Congress and Exposition (ECCE))

   Electric Vehicles (EV s) that are wholly charged from renewable energy resources to avoid indirect emissions are the most effective solution for climate change and energy insecurity. This paper proposes a four-port isolated PV -based EV charging architecture that contains an LLC input stage to harvest solar energy with high efficiency because of its dual PV input ports with independent MPPT capabilities that share a common resonant tank. This architecture also includes a GaN -based flying capacitor multilevel (FCML) output stage with two GaN-based FCML converter paths, DC and AC paths. These two paths transfer power with high efficiency to two output ports, a DC port for direct DC charging and an AC port for level-2 AC charging. The system has been verified by building a 2 kW prototype module, and experimental results are presented. 

   more » « less
3. A Single-Aperture, Single-Pixel Reader for Optical Frequency Identification

   https://doi.org/10.1109/ISCAS51556.2021.9401470  

   Fan, Xiaozhe; Hidalgo, James; Leon-Salas, Walter D. (May 2021, 2021 IEEE International Symposium on Circuits and Systems (ISCAS))

   null (Ed.)

   This paper presents a single-aperture, single-pixel reader for communication with Optical Frequency Identification (OFID) tags. OFID tags use solar cells to transmit and receive information wirelessly as well as to harvest radiant energy. Due to its single-aperture architecture, the reader's optical system provides a shared optical path for reception and transmission. Also, physical alignment between the reader and an OFID tag is visually guided using the reader's emitted light, securing a robust data link as long as the OFID tag is illuminated. In this paper, a description of the reader's optical and electronic sub-systems are presented. The transmitter and receiver circuits are described in detail. The transmitter, built with a linear LED driver, achieves a power efficiency of nearly 87%. The receiver, featuring a third-order bandpass filter, reduces both low-frequency and high-frequency ambient noise. A prototype of the reader was fabricated and housed in a custom 3D-printed enclosure. Test results show that the reader is able to receive modulated luminescent signals from an OFID tag at a distance of 1 m and at a data rate of 3 kbps. 

   more » « less
4. Virtual Admittance Based Switch Fault Detection for Hybrid UAVs

   Kim, T; Parvathareddy, S (October 2024, 2024 IEEE Energy Conversion Conference and Expo (ECCE))

   Unmanned aerial vehicles (UAVs) are widely used for various applications, such as military surveillance and reconnaissance; delivery of packages; monitoring of plants and buildings; and search and rescue. Besides basic battery-electric propulsion, in order to improve range and endurance, hybrid electric propulsion systems based on combinations of batteries, fuel cells, solar cells, and ultracapacitors are increasingly being applied to these UAVs. For small- and medium-scale UAVs, the solar and fuel cell converters have non-isolated DC-DC converters that include a high-frequency switching device. In this paper, a novel switch fault detection technique based on virtual admittance is proposed for DC-DC converters. A fault index function is formulated based on the virtual admittance to minimize potential influence by highly dynamic load change while reducing computation complexity to implement the technique in cost-effective UAVs. The proposed technique has been verified by simulations and experiments to validate the feasibility of the approach. 

   more » « less
5. Bifacial flexible CIGS thin-film solar cells with nonlinearly graded-bandgap photon-absorbing layers

   https://doi.org/10.1088/2515-7655/ad29fd  

   Ahmad, Faiz; Monk, Peter B.; Lakhtakia, Akhlesh (March 2024, Journal of Physics: Energy)

   Abstract The building sector accounts for 36% of energy consumption and 39% of energy-related greenhouse-gas emissions. Integrating bifacial photovoltaic solar cells in buildings could significantly reduce energy consumption and related greenhouse gas emissions. Bifacial solar cells should be flexible, bifacially balanced for electricity production, and perform reasonably well under weak-light conditions. Using rigorous optoelectronic simulation software and the differential evolution algorithm, we optimized symmetric/asymmetric bifacial CIGS solar cells with either (i) homogeneous or (ii) graded-bandgap photon-absorbing layers and a flexible central contact layer of aluminum-doped zinc oxide to harvest light outdoors as well as indoors. Indoor light was modeled as a fraction of the standard sunlight. Also, we computed the weak-light responses of the CIGS solar cells using LED illumination of different light intensities. The optimal bifacial CIGS solar cell with graded-bandgap photon-absorbing layers is predicted to perform with 18%–29% efficiency under 0.01–1.0-Sun illumination; furthermore, efficiencies of 26.08% and 28.30% under weak LED light illumination of 0.0964 mW cm⁻²and 0.22 mW cm⁻²intensities, respectively, are predicted. 

   more » « less