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Computer and Experimental Modelling of Heat Leakage from Porous Substrates of LED Lighting Devices
摘要： In this paper we propose a mathematical and physical model of a porous substrate, evaluate influence of the pores size and quantity on the substrate’s specific surface and present experimental results of the heat leakage kinetics by the porous substrate. Performances of the porous aluminium oxide printed circuit board with the record heat conductivity of 120 W/mK are presented.
关键词： porous substrate,printed board,physical model,heat conductivity,LED lighting device
更新于2025-09-12 10:27:22
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Catalyst-Free Growth of MoS2 Nanorods Synthesized by Dual Pulsed Laser-Assisted Chemical Vapor Deposition and Their Structural, Optical and Electrical Properties
摘要： Molybdenum disulfide (MoS2) nanorods (NRs) were synthesized from bulk MoS2 using laser-assisted chemical vapor deposition. A q-switched Nd:YAG laser with combined beam wavelengths of 1064 nm and 532 nm was used to ablate a solid MoS2 target. A vapor–solid process at a furnace temperature of 1000°C was found to support the growth of MoS2 NRs without the need for any metal catalyst. Powder x-ray diffraction analysis (PXRD), field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy were used to characterize the structural and optical properties of MoS2 NRs. The PXRD revealed the crystallinity and phase purity of the as-synthesized NRs, while electron microscopy showed that MoS2 NRs had lengths in the range of 0.5–1.2 μm and widths between 40 nm and 160 nm. UV–Vis absorption spectra exhibited broad absorption, and PL measurements showed a sharp emission peak at 379 nm. Tauc plot calculations determined that the MoS2 NRs showed a direct transition. The electrical conductivity of the NRs was found to be 317.95 S/cm. In comparison with the MoS2 nanoparticles, the MoS2 NRs showed higher conductivity due to the in-plane electron transport, which is higher in NRs.
关键词： optical studies,MoS2,conductivity,electron microscopy,nanorods,LACVD
更新于2025-09-12 10:27:22
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Magnetron sputtered Sb2Se3-based thin films towards high performance quasi-homojunction thin film solar cells
摘要： Sb2Se3 is a promising candidate for environment-friendly and cost-e?ciently thin ?lm photovoltaics thanks to its material advantages and superior optoelectronic properties. However, it has intrinsically low electrical conductivity, which leads to unsatisfactory device performance and limited scope of applications. Herein, we demonstrated an e?ective strategy of electrical conductivity-induced Sb2Se3-based photovoltaic performance improvement. Three Sb2Se3-based targets with chemical composition of Sb2Se3, Sb2Se3.3 and Sb2(Se0.9I0.1)3 have been ?rstly prepared by using high-temperature melting technique. Then the high-quality thin ?lms can be obtained through an e?ective Radio Frequency (RF) magnetron sputtering process. A novel Sb2Se3 quasi-homojunction thin ?lm solar cell was fabricated for the ?rst time and the highest power conversion e?ciency reaches already a highly interesting 2.65%. The combined features of unique quasi-homojunction device structure and advantageous full-vacuum preparation process further demonstrated its attractive potential for thin ?lm photovoltaic applications.
关键词： Sb2Se3,Quasi-homojunction,Magnetron sputtering,Thin ?lm solar cells,Electrical conductivity
更新于2025-09-12 10:27:22
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What limits the efficiency of GaN-based superluminescent light-emitting diodes (SLEDs)?
摘要： Gallium-nitride-based SLEDs are attractive light sources for augmented reality displays and other applications. However, the electrical-to-optical power conversion efficiency (PCE) of SLEDs is still far below the record-high values reported for LEDs. Utilizing advanced numerical device simulation, this paper investigates the internal physical pro- cesses that cause the low PCE of SLEDs. The poor hole conductivity strongly reduces the electrical efficiency, similar to laser diodes. However, in contrast to laser diodes, the rising carrier density in the active layers is identified as main reason for enhanced Auger recom- bination that severely limits the internal quantum efficiency. Design improvement options are demonstrated.
关键词： Superluminescent light-emitting diode,Auger recombination,InGaN/GaN,Laser diode,Self-heating,Power conversion efficiency,SLED,Hole conductivity
更新于2025-09-12 10:27:22
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zT = 1.1 in CuInTe <sub/>2</sub> Solid Solutions Enabled by Rational Defect Engineering
摘要： In this study, the synthesis and thermoelectric performance of CuInTe2?In2Te3 and Cu0.85Ag0.15InTe2?In2Te3 solid solutions are reported. The experimental results associated with model fitting reveal that the cation vacancies generated by creating solid solutions with a compound with a smaller cation-to-anion ratio can strongly scatter phonons with high frequency, which remarkably decrease the total as well as lattice thermal conductivity of the CuInTe2 system and finally realize an enhanced thermoelectric properties compared to the pristine sample. Furthermore, substitutional Ag/Cu defects integrated with vacancies lead to a further reduction in lattice thermal conductivity. With the benefit from the rational defect design, a high figure of merit of 1.1 is gained at 840 K for the sample (Cu0.85Ag0.15InTe2)0.98?(In2Te3)0.02. In addition, a 188% improvement on average zT is obtained. This work provides an effective method for boosting thermoelectric performance of chalcopyrite compounds by defect engineering on multiple types of defects.
关键词： defect engineering,thermoelectric performance,vacancy phonon scattering,thermal conductivity,CuInTe2
更新于2025-09-12 10:27:22
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Enhanced Physical and Thermal Performance of Expanded Graphite-Based Heat Sink for LED Radiator
摘要： An experimental study was carried out to investigate the heat transfer characteristics of Cu and Al–modified expanded graphite heat sinks. In this study, the heat sinks were composed of expanded graphite as an active material, Cu and Al as heat transfer enhancement material and resin as a binder. Graphite with high purity was obtained via treated with different amount of Na2CO3. The as-prepared heat sinks were characterized by XRD, pH, SEM, electrical resistivity, bending strength and thermal analysis. The metal Al modified expanded graphite composite heat sink in our experiment exhibited a good rate of capability in physical and thermal performances. Sample GA5-300 showed highest thermal diffusivity and thermal conductivity.
关键词： Expanded graphite,Heat transfer,Thermal diffusivity and conductivity
更新于2025-09-12 10:27:22
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Effect of imidazole based polymer blend electrolytes for dye-sensitized solar cells in energy harvesting window glass applications
摘要： The exploration of polymer electrolyte in the field of dye sensitized solar cell (DSSC) can contribute to increase the invention of renewable energy applications. In the present work, the influence of imidazole on the poly (vinylidene fluoride) (PVDF)- poly (methyl methacrylate) (PMMA)-Ethylene carbonate (EC)-KI-I2 polymer blend electrolytes have been prepared. The different weight percentage of imidazole added into polymer blend electrolytes has been prepared by solution casting. The prepared films were characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), UV-visible spectra, photoluminescence spectra and impedance spectroscopy. The surface roughness texture of the film was analyzed by atomic force microscopy (AFM). The ionic conductivity of the optimized polymer blend electrolyte by impedance measurement, which is 1.95×10-3 S cm-1 at room temperature. The polymer electrolyte containing 40 wt% of imidazole content exhibits the highest photo-conversion efficiency of 3.04% under the illumination 100 mWcm-2. Moreover, a considerable enhancement in the stability of the DSSC device was demonstrated.
关键词： Polymer blend electrolyte,Imidazole,Dye-sensitized solar cell,Surface roughness,Ionic conductivity
更新于2025-09-12 10:27:22
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Role on nanofluids in cooling solar photovoltaic cell to enhance overall efficiency
摘要： The electrical conversion efficiency of Solar photovoltaic module strongly depends on the operating temperature. Only up to 20% of the incident solar irradiation is converted to electricity and rest energy either reflected back to atmosphere or converted into heat and thereby increasing the cell temperature. As the cell temperature rises, the electrical efficiency decreases. There is need to cool down temperature of the solar photovoltaic panel to get maximum electrical conversion efficiency. Researchers have implemented many techniques for cooling solar PV by active and passive cooling technique. Active cooling uses air, water, nanofluids etc for cooling where as in passive cooling uses of phase change materials like paraffin wax, eutectics, organic materials, cotton wick etc for the cooling purpose. Nanofluids are used to bring down the temperature of the panel by increasing the thermal conductivity of base fluids. In this paper, emphasis has been given to present the effect of nanofluids as coolant in solar photovoltaic panel.
关键词： Nanofluids,Electrical conversion efficiency,Solar Photovoltaics,Thermal conductivity,Overall efficiency
更新于2025-09-12 10:27:22
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Laser-Scribed Graphene Electrodes Derived from Lignin for Biochemical Sensing
摘要： Laser scribing of porous graphene electrodes on flexible substrates is of great interest for developing disposable electrochemical biosensors. In this work, we present a new patterning process for highly conductive nitrogen-doped graphene derived from a lignin-based precursor. A CO2 laser scribing process was performed under ambient conditions to produce the porous graphene electrodes from lignin. The obtained nitrogen-doped laser-scribed graphene (N-LSG) is binder-free, hierarchical, and conductive. The interconnected carbon network displayed enhanced electrochemical activity with improved heterogeneous electron transfer rate. These features can be attributed to the high-conductivity of porous N-LSG (down to 2.8 ? per square) and its enriched active edge plane sites. Furthermore, the N-LSG electrodes were decorated with MXene/Prussian Blue (Ti3C2Tx/PB) composite via a simple spray coating process, designed for sensitive detection of analytes. The Ti3C2Tx/PB modified N-LSG electrodes were functionalized with catalytic enzymes for detecting glucose, lactate, and alcohol. The enzyme/Ti3C2Tx/PB/N-LSG electrodes exhibited remarkably enhanced electrochemical activity toward the detection of these biomarkers, making them highly competitive with previously reported on-chip carbon-based biosensors. Therefore, our sensors demonstrate excellent potential for applications in personalized healthcare.
关键词： laser-scribed graphene,MXene,alcohol,lactate,glucose,lignosulfonate,biosensor,high conductivity
更新于2025-09-12 10:27:22
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Effect of Laser Ablation on Microwave Attenuation Properties of Diamond Films
摘要： Thermal conductivity is required for developing high-power microwave technology. Diamond has the highest thermal conductivity in nature. In this study, a diamond ?lm was synthesized by microwave plasma chemical deposition, and then long and short conductive graphite ?bers were introduced to the diamond ?lms by laser ablation. The permittivity of the samples in the K-band was measured using the transmission/re?ection method. The permittivity of diamond ?lms with short graphite ?bers increased. The increase in real part of permittivity can be attributed to electron polarization, and the increase in the imaginary part can be ascribed to both polarization and electrical conductivity. The diamond ?lms with long graphite ?bers exhibited a highly pronounced anisotropy for microwave. The calculation of microwave absorption shows that re?ection loss values exceeding ?10 dB can be obtained in the frequency range of 21.3–23.5 GHz when the graphite ?ber length is 0.7 mm and the sample thickness is 2.5 mm. Therefore, diamond ?lms can be developed into a microwave attenuation material with extremely high thermal conductivity.
关键词： high thermal conductivity,laser ablation,diamond ?lms,microwave attenuation,permittivity
更新于2025-09-12 10:27:22