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Size and shape control of monoclinic vanadium dioxide thermochromic particles for smart window applications
摘要： Monoclinic vanadium dioxide (VO2 (M)) was synthesized by the thermolysis of vanadyl ethylene glycolate, which was obtained easily by the precipitation of a vanadium precursor in ethylene glycol solution under atmospheric conditions. The particle size and shape were easily controlled by altering the molar concentration of the vanadium precursor. Thereafter, VO2 (M) composite films were prepared by mixing with poly(vinylpyrrolidone). A high concentration of the vanadium precursor produced small spherical nanoparticles ≈30 nm in size, while lower concentrations afforded large rod-like particles. The composite films fabricated with the VO2 (M) nanoparticles exhibited high luminous transmittance (Tlum = 79%) and IR modulation ability (ΔTIR = 5.6%). This work demonstrates that these VO2 (M) composite films show promise for application in smart windows.
关键词： solar modulation ability,Energy efficiency,size and shape tuning,high luminous transmittance,VO2 (M) particle,thermochromic coating
更新于2025-09-23 15:21:21
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Optimized thermochromic properties of VO2/CoFe2O4 nanocomposite films via band gap engineering
摘要： VO2/CoFe2O4 nanoparticle composites were synthesized by hydrothermal method combined with annealing treatment. The nanocomposites consist of quasi-spherical nanoparticles with an average size of about 70 nm. The thermochromic properties of the nanocomposite films can be modulated by changing film thickness and the content of CoFe2O4 in the nanocomposites. The band gap of the VO2/CoFe2O4 nanocomposites increases with increasing CoFe2O4 additive content. The introduction of CoFe2O4 into VO2 matrix can not only lower the phase transition temperature, but also optimize the luminous transmittance and solar modulation ability of the VO2/CoFe2O4 nanocomposites as well. Our findings demonstrate a promising avenue in constructing VO2-based smart films with excellent thermochromic performance.
关键词： Solar modulation ability,VO2/CoFe2O4 nanocomposite,Luminous transmittance,Phase transition temperature
更新于2025-09-23 15:21:21
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Low Voltage Graphene-Based Amplitude Modulator for High Efficiency Terahertz Modulation
摘要： In this paper, a high-e?ciency terahertz amplitude modulation device based on a ?eld-e?ect transistor has been proposed. The polarization insensitive modulator is designed to achieve a maximum experimental modulation depth of about 53% within 5 V of gate voltages using monolayer graphene. Moreover, the manufacturing processes are inexpensive. Two methods are adopted to improve modulation performance. For one thing, the metal metamaterial designed can e?ectively enhance the electromagnetic ?eld near single-layer graphene and therefore greatly promote the graphene’s modulation ability in terahertz. For another, polyethylene oxide-based electrolytes (PEO:LiClO4) acts as a high-capacity donor, which makes it possible to dope single-layer graphene at a relatively low voltage.
关键词： solid electrolyte,terahertz,single-layer graphene,transmittance,metamaterial,amplitude modulation,?eld-e?ect transistor
更新于2025-09-23 15:21:01
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Superconducting one-dimensional photonic crystal with coupled semiconductor defects
摘要： We investigate the impact of the insertion of a semiconductor defect on the transmittance spectrum of a one-dimensional photonic crystal composed by alternating layers of superconducting materials. We report that the effect of the insertion of the semiconductor defect originates a defective mode in the photonic band gap that exhibits a shift towards long-wavelength regimes. Unexpectedly, for high values of temperatures, it is observed that the defective mode reduces its confinement as well as influences the optical response of the photonic crystal rather than the pressure. We also extend our analysis to the case of two coupled defects of GaAs, and it is studied the effect of the relative distance between these two defects. Our numerical results reveal that the defective mode has a significant reduction in its quality factor as well as it displays an asymmetry in the transmittance spectrum when the defects are close to each other.
关键词： Transfer matrix method,Defect mode,Semiconductor,Transmittance spectrum,One-dimensional photonic crystal,Superconductor
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Performance characterization for bifacial photovoltaic modules
摘要： The performance of bifacial photovoltaic modules were characterized. The optical transmittance was measured for front and back side illumination. The temperature coefficients were obtained in order to predict the real power that can be produced in an installation under operating conditions. The internal quantum efficiency distribution was measured to distinguish recombination activity which occurred at the silicon via two-dimensional LBIC method.
关键词： optical transmittance spectra,temperature coefficient,bifacial perc solar cells,quantum efficiency
更新于2025-09-23 15:21:01
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Low-Terahertz Transparent Graphene-Based Absorber
摘要： A new, transparent, metal-free absorber, based on the use of multilayer graphene/dielectric laminates (GLs), is proposed for applications in the low-terahertz frequency range. The designed absorber has a total thickness of around 70 μm and consists of a front matching dielectric layer followed by a GL, a dielectric spacer and a back GL. The laminates are periodic structures constituted of graphene sheets separated by 50-nm-thick polyethylene terephthalate (PET) interlayers, while the matching layer and the spacer are one-quarter-wavelength thick and made of PET. The GLs are modeled as homogeneous-equivalent single layers (ESLs) characterized by their sheet resistances Rs. An innovative analytical method is proposed in order to select Rs values optimizing the electromagnetic wave absorption either in low-gigahertz or low-terahertz frequency range. The frequency spectra of the absorption, reflection and transmission coefficients are computed in the range up to 4 THz by using different values of Rs. Then, realistic Rs values of chemically doped graphene monolayers over PET substrates are considered. The designed absorbers are characterized by an absorption coefficient with a peak value of about 0.8 at the first resonant frequency of 1.1 THz, and a 1.4 THz bandwidth centered at 1.5 THz with reflection coefficient below - 10 dB. Moreover, the optical transmittance of the proposed absorbers are computed by means of the optical matrix theory and it is found to be greater than 86% in all the visible ranges.
关键词： absorption,reflection and transmission performance up to 4 THz,low-terahertz transparent absorber,transmission line approach,graphene-polyethylene terephthalate laminate,laminate effective medium model,optical transmittance in the visible range
更新于2025-09-23 15:21:01
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Fabrication and characterization of graphene quantum dots thin film for reducing cross-sectional heat transfer through smart window
摘要： Graphene and its derivatives have been reported as materials with excellent electrical and thermal conductivity, allowing for various promising applications. In particular, the large-scale surface coating of graphene-based materials can be employed to minimize cross-sectional heat transfer through the glass window. This study introduces a facile and cost-effective method to fabricate graphene quantum dots (GQDs) thin film on Fluorine-doped Tin Oxide (FTO) glass via casting of the GQDs dispersion and stabilizing with poly-vinyl-pyrrolidone (PVP). The thin film possesses excellent optical properties of GQDs and allows more than 80 % of visible transmittance. The presence of the GQDs thin film shows effective reduction in the cross-sectional thermal diffusivity of FTO glass, from 0.55 mm2/s to zero when measured with laser flash over a 4-second period. This low cost and eco-friendly GQDs thin film will be a promising material for heat management in smart window applications.
关键词： Smart window,Cross-Sectional heat transfer,Graphene quantum dots,Poly-Vinyl-Pyrrolidone,Visible transmittance
更新于2025-09-23 15:21:01
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Optical properties of diamond-like carbon films prepared by pulsed laser deposition onto 3D surface substrate
摘要： It is difficult to grow uniform film by pulsed laser deposition because the spatial distribution of the laser-induced plume is a forward-directed cone-shape. A 3D-motional deposition setup was founded, and the correlative mathematical model of the film thickness on the 3D curved surface was deduced. Based on simulation and optimization, the diamond-like carbon (DLC) film was grown onto the large curved silicon substrate. According to the infrared transmittance spectra, the optical constants of the DLC film samples at different regions on the curved substrate were similar, indicating that the DLC film prepared onto the curved surface was homogeneous. Meanwhile, the deviation of average transmittance in the medium infrared band was below 2.3%, which could improve the imaging performance of the infrared detection. This research is useful to expand the application of the pulsed laser deposition in the optical field.
关键词： uniform transmittance,Raman spectroscopy,3D curved surface,Pulsed laser deposition,DLC film,infrared spectrum
更新于2025-09-23 15:21:01
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Tunable luminescence and transmittance nature of CdS:PMMA nanocomposites for optoelectronic applications
摘要： Optical and energy storage materials based on semiconductors are of great interest today. The present report explains the semiconductor nanocomposite centered on highly transparent Poly(methyl methacrylate) (PMMA) matrix and Cadmium Sulphide (CdS) nano particles. The solid ?lms of CdS:PMMA composite was prepared using simple and cost e?ective solution casting technique. The surface morphology and the presence of CdS particles in PMMA matrix was analysed using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectra (EDX). The size of the particles was analysed using Atomic Force Microscopy (AFM) and Transmission Electron Microscope (TEM) and they revealed the presence of nano sized particles. The narrow size distribution of particles was identi?ed from TEM and AFM analysis. The transmittance of the CdS:PMMA nanocomposite solid ?lms was found to be above 90%. The blue and green emission of CdS:PMMA nanocomposite solid ?lms were observed from Photoluminescence (PL) spectra.
关键词： Composite materials,Polymeric composite,Luminescence,Green emission,Particle distribution,Transmittance
更新于2025-09-23 15:21:01
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Optical and Electrical Performance of ZnO Films Textured by Chemical Etching
摘要： Zinc oxide (ZnO) films were prepared by radio frequency (RF) magnetron sputtering on the glass substrate as transparent conductive oxide films. For silicon solar cells, a proper surface texture is essential to introduce light scattering and subsequent light trapping to enhance the current generation. In this study, the magnetron-sputtered ZnO films were textured by wet-chemical etching in diluted hydrochloric acid (HCl) for better light scattering. The diffuse transmittance of the surface textured ZnO films was measured to evaluate the light scattering. The influence of hydrochloric acid concentration on the morphology, optical and electrical properties of the surface-textured ZnO film was investigated. The ZnO film etched in 0.05M HCl solution for 30 s exhibited average diffuse transmittance in the visible wavelength range of 9.52 % and good resistivity of 1.10 x 10-3 Ω·cm while the as-deposited ZnO film had average diffuse transmittance of 0.51 % and relatively high resistivity of 5.84 x 10-2 Ω·cm. Experimental results illustrated that the optical and electrical performance of ZnO films can be significantly improved by introducing the surface texture through the wet-chemical etching process.
关键词： surface texture,light scattering,diffuse transmittance,resistivity,zinc oxide
更新于2025-09-23 15:21:01