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Structural and optical studies on PVA capped SnS films grown by chemical bath deposition for solar cell application
摘要： Tin monosulphide (SnS) thin films capped by PVA have been successfully deposited on glass substrates for cost effective photovoltaic device applications by a simple and low-cost wet chemical process, chemical bath deposition (CBD) at different bath temperatures varying in the range, 50–80 °C. X–ray diffraction analysis showed that the deposited films were polycrystalline in nature, showing orthorhombic structure with an intense peak corresponding to (040) plane of SnS. These observations were further confirmed by Raman analysis. FTIR spectra showed the absorption bands which corresponds to PVA in addition to SnS. The scanning electron microscopy and atomic force microscopy studies revealed that the deposited SnS films were uniform and nanostructured with an average particle size of 4.9 to 7.6 nm. The optical investigations showed that the layers were highly absorbing with the optical absorption coefficient ~105 cm–1. A decrease in optical band gap from 1.92 to 1.55 eV with an increase of bath temperature was observed. The observed band gap values were higher than the bulk value of 1.3 eV, which might be due to quantum confinement effect. The optical band gap values were also used to calculate particle size and the results are discussed.
关键词： structural properties,optical properties,SnS thin films,polyvinyl alcohol,capping agent,chemical bath deposition
更新于2025-11-21 11:18:25
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Mono and co-substitution of Sr2+ and Ca2+ on the structural, electrical and optical properties of barium titanate ceramics
摘要： In this work, Ba0.9Sr0.1TiO3, Ba0.7Sr0.3TiO3, Ba0.5Sr0.5TiO3, Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr2+ and Ca2+) on the structural, electrical and optical properties of BaTiO3 ceramics. Sr2+ added samples showed a tetragonal structure which became slightly distorted with increasing Sr2+ concentration and finally achieved a cubic structure for x = 0.50. Ba0.5Ca0.5TiO3 also retained their tetragonality with limited solubility. Presence of second phase, CaTiO3 demonstrated the fact of restricted solubility. The concurrent effect of Sr2+ and Ca2+ didn't alter the tetragonal structure. Sr2+ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba1-xSrxTiO3 was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48 eV to 3.28 eV with increasing Sr2+ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ～547 for Ba0.5Ca0.25Sr0.25TiO3 ceramics. Both Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr2+ and Ca2+ was a good approach enhancing materials electrical as well as optical property.
关键词： Dielectric properties,Grain size,X-ray diffraction,Optical properties,Sintering
更新于2025-11-21 11:18:25
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Preserved two-photon optical properties of hydrophilic proteins-conjugated quantum dots
摘要： Nonlinear optical properties of colloidal CdSe quantum dots conjugated with proteins were investigated in a wide spectral range with the two-photon excited emission technique using a tunable femtosecond laser system in the range from 700 to 1000 nm. The most signi?cant value of the two-photon absorption cross section σ2 for 2.9 nm size hydrophilic CdSe quantum dot was equal to 4 505 GM, while the two-photon excitation action cross section σ2·QY was found to be 0.101 GM at 900 nm. The nonlinear absorption properties are present as appropriate cross sections normalized per molecular weight which allows comparison of the nonlinear properties of the studied quantum dots with various nanosystems or organic dyes. The properties of these proteins covering hydrophilic colloidal quantum dots can be potentially useful for nonlinear bioimaging.
关键词： Hydrophilization,Semiconducting quantum dots,Nonlinear optical properties,Nanophotonics,Proteins
更新于2025-11-20 15:33:11
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Crosslink network and phenyl content on the optical, hardness, and thermal aging of PDMS LED encapsulant
摘要： This work aims to synthesize new series of polysiloxane copolymer through hydrosilylation reaction based on different level of crosslink densities and phenyl content. The results revealed that polysiloxanes resins with phenyl rings increased viscosity up to 3800 cps while displaying a relatively high refractive index of 1.531. The asymmetric phenyl substitution onto chain backbone led to formation of densely packed structure resulting in reduced water absorption and gas permeability of PDMS resins. High level of crosslinking contributed to a high shore A hardness and adhesion strength. It displayed transparency of 97% whose percentage reduction was 1.6% under thermal and 0.6% UV aging. No obvious discoloration was observed during accelerated thermal aging up to 210 min at 80 (cid:1)C. These results are key attributes that make the synthesized polysiloxane series as ideal candidate for high brightness LED encapsulant. ? 2019 Wiley Periodicals, Inc. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47895.
关键词： copolymers,thermal properties,ring-opening polymerization,optical properties,synthesis and processing techniques
更新于2025-11-19 16:56:42
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Nitrogen-doped graphene quantum dots: Optical properties modification and photovoltaic applications
摘要： In this work, we utilize a bottom-up approach to synthesize nitrogen self-doped graphene quantum dots (NGQDs) from a single glucosamine precursor via an eco-friendly microwave-assisted hydrothermal method. Structural and optical properties of as-produced NGQDs are further modified using controlled ozone treatment. Ozone-treated NGQDs (Oz-NGQDs) are reduced in size to 5.5 nm with clear changes in the lattice structure and ID/IG Raman ratios due to the introduction/alteration of oxygen-containing functional groups detected by Fourier-transform infrared (FTIR) spectrometer and further verified by energy dispersive X-ray spectroscopy (EDX) showing increased atomic/weight percentage of oxygen atoms. Along with structural modifications, GQDs experience decrease in ultraviolet–visible (UV–vis) absorption coupled with progressive enhancement of visible (up to 16 min treatment) and near-infrared (NIR) (up to 45 min treatment) fluorescence. This allows fine-tuning optical properties of NGQDs for solar cell applications yielding controlled emission increase, while controlled emission quenching was achieved by either blue laser or thermal treatment. Optimized Oz-NGQDs were further used to form a photoactive layer of solar cells with a maximum efficiency of 2.64% providing a 6-fold enhancement over untreated NGQD devices and a 3-fold increase in fill factor/current density. This study suggests simple routes to alter and optimize optical properties of scalably produced NGQDs to boost the photovoltaic performance of solar cells.
关键词： photovoltaics,optical properties,ozone treatment,nitrogen-doped graphene quantum dots,solar cells
更新于2025-11-19 16:56:42
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Synthesis and Optical Properties of Iodinated Multi-walled Carbon Nanotubes
摘要： This paper reports synthesis and optical properties of iodinated multi-walled carbon nanotubes (MWCNT). Multi-walled carbon nanotubes were synthesized by aerosol – assisted chemical vapor deposition method and iodinated by crystalline iodine under increased pressure (approximately ~20 bar) at 400°C. X-ray diffraction analysis, Raman and Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy were applied to characterize the iodinated MWCNTs.The results proved the presence of iodine atoms in iodinated MWCNTs. UV-VIS absorption and photoluminescence properties have been studied in pristine MWCNTs and iodinated MWCNTs suspensions in ethanol. Firstly, photoluminescence intensity of the iodinated MWCNTs remarkably enhanced with the appearance of C–I bonds on the surface of MWCNTs, due to the high concentration of intercalated iodine atoms (approximately 30 wt %). The photoluminescence intensity enhancement of peaks at 430 and 520 nm is highly dependent on defects formed by C–I bonds.
关键词： C–I bonds,photoluminescence,iodinated multi-walled carbon nanotubes,optical properties
更新于2025-11-19 16:56:42
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Optical Properties of Quantum Dots with a Core–Multishell Structure
摘要： In the last decade, colloidal semiconductor nanocrystals (quantum dots) have been not only studied fundamentally but also applied in photovoltaics, optoelectronics, and biomedicine. Beginning with simple approaches to the deposition of protective shells, e.g., ZnS on CdSe cores, searches for ways to increase the quantum yield of photoluminescence of quantum dots have resulted now in the development of new types of quantum dots characterized not only by record high extinction coefficients but also by high photoluminescence quantum yields. In this work, the optical properties of core–multishell quantum dots have been analyzed. These quantum dots have been specially designed to reach the maximum possible localization of excited charge carriers inside luminescent cores, which makes it possible to reach a photoluminescence quantum yield close to 100%. Core–multishell quantum dot samples with a shell thickness of 3–7 monolayers have been fabricated. Changes in the characteristics of optical transitions in such quantum dots with an increase in the number of layers of the shell have been studied. The effect of the thickness of the shell on the optical properties of prepared quantum dots has been analyzed. In particular, analysis of photoluminescence lifetimes of such quantum dots has revealed a possible alternative mechanism of radiation of core–multishell quantum dots based on the slow charge carrier transfer from the excited outer layer of the CdS shell to the CdSe core.
关键词： quantum dots,optical properties,core–multishell structure,photoluminescence
更新于2025-11-19 16:56:42
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Complex Optical and Thermal Studies on As-Synthesized Conducting Polythiophene
摘要： A series of conducting polythiophene (PTh) samples have been synthesized using an in situ chemical oxidative polymerization technique in aqueous solution. The characterization of the as-synthesized optimized sample has been carried out by Fourier transform infrared spectroscopy, x-ray diffraction and thermogravimetric–differential thermal analysis techniques. Also, the complex optical parameters of all the as-synthesized polymeric samples have been investigated by using ultraviolet–visible spectroscopy. The as-synthesized polymeric samples exhibited absorption around 220–280 nm. The optical band gap was found to ranges from 5.06 eV to 5.24 eV. The maximum optical conductivity for the sample with a stoichiometric ratio of thiophene to FeCl3 of 70:30 wt.% was found to be 5.973 9 108 S cm?1 at 280 nm. The experimental results reveal that the thermal and optical performance of conducting PTh can be dramatically enhanced for the sample with a stoichiometric ratio of thiophene to FeCl3 of 70:30 wt.%. The improved complex optical properties of as-synthesized samples of conducting PTh validate their potential utilization in optoelectronic devices.
关键词： thermal analysis,complex optical properties,Polythiophene
更新于2025-11-19 16:56:35
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Improvement of Optical and Thermal Properties for Quantum Dots WLEDs by Controlling Layer Location
摘要： The inorganic halide perovskite quantum dots (QDs) have been considered as a promising substitute for white light-emitting diodes (WLEDs). In this article, the green CsPbBr3 QDs and red K2SiF6:Mn4+ (KSF) phosphor were used to fabricate the conversion layers. Because the layers location is fundamental to the absorption priority of blue light, the location of KSF and QDs were controlled and the QDs-up type and QDs-down type WLEDs were made. The optical power, luminous efficiency, CCE and luminous intensity in the middle of QDs-up type are 13.83 mW, 13.54 lm/W, 11.94% and 2.65 cd, meaning 24.26%, 25.72%, 2.63% and 23.83% higher than those of QDs-down type, respectively. In addition, the QDs-up type has a lower correlated color temperature (CCT) shift of 734 K and a decreased highest temperature of 56.8℃ (51.5% and 14.9% lower). These key property differences indicate that the QDs-up type is more suitable for the application in display and backlight. In order to explore the reasons for these differences, the emission spectra, CCE, reflection rate, absorption rate and temperature curves of QDs or KSF films were also analyzed, which provided a better understanding of designing package structures.
关键词： layer location,thermal properties,quantum dots WLEDs,optical properties
更新于2025-11-19 16:46:39
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Phosphotellurite glass and glass-ceramics with high TeO <sub/>2</sub> content: thermal, structural and optical properties
摘要： Phosphotellurite based glasses have interesting features such as low characteristic temperatures, large glass forming ability, high thermal stability against crystallization and broad transparency window from ultraviolet (UV) to near-infrared (NIR), which makes them promising materials for photonic applications. In this work, phosphotellurite binary glasses, having composition (100 – x) TeO2–x Ba(PO3)2 with x varying from 1 to 20 mol %, were synthesized by the conventional melt-quenching method in covered gold crucibles under air. Optical, physical and structural properties of the new glass samples were investigated by differential scanning calorimetry, X-rays diffraction, Raman spectroscopy, transmission electron microscopy, linear optical absorption from UV to NIR, IR transmittance, and optical limiting experiments. Transparent glass-ceramics in the visible range were obtained for phosphotellurite samples containing 2, 4 and 6 mol % of Ba(PO3)2 and the phase crystallization was investigated through Rietveld analysis and transmission electron microscopy. The incorporation of Ba(PO3)2 into the TeO2 network drastically increases the thermal stability against devitrification and helps to shift the infrared multiphonon absorption edge to longer wavelengths. Nonlinear measurements performed with a picosecond laser at 532 nm indicate large effective nonlinear absorption coefficients for all samples. In summary, the dependence of the spectroscopic properties on the samples’ compositions revealed a promising transparent glass and glass-ceramics for photonic applications.
关键词： transparent glass-ceramics,phosphotellurite glass,optical properties,nonlinear optical response
更新于2025-11-14 17:03:37