Optical Parameters Research Articles

Emergence of defects-mediated diluted ferromagnetic semiconductor (ZnS: La3+) Quantum Dots: A versatile platform for optoelectronic and spintronic applications

For the first time, La3+ ions incorporated into semiconductor Zinc Sulfide-Quantum Dots (ZnS-QDs), Zn1-xLaxS, were effectively produced via a straightforward co-precipitation approach, with diverse La ratios (0.00 ≤ x ≤ 0.15 at%). The phase analysis of the acquired QDs, conducted through Raman analysis and X-ray diffractometer (XRD), revealed a singular cubic ZnS structure, devoid of any impurities. Morphology studies by HR-TEM showed a nearly spherical particle with a size of approximately 6.4 nm. X-ray photoelectron spectroscope (XPS) investigation disclosed the significant presence of sulfur vacancies, along with the existence of the trivalent oxidation state of lanthanum (La3+) within the ZnS structure. Optical absorbance studies exhibited that all QDs were positioned approximately at the absorption edges of around 270 nm (4.59 eV), surpassing the bulk ZnS energy gap of 337 nm (3.67 eV), harmonically with the quantum confinement effect. Additionally, a pronounced band gap narrowing was observed with increasing the doping level of La ions, on account of the presence of defects that result in the creation of localized states inside the ZnS band structure. The optical results indicated the capability to fine-tune the optical energy gap, dispersion parameters, and enhance the nonlinear optical parameters, which makes these QDs well-suited for use in optoelectronic devices. Furthermore, the photoluminescence (PL) spectra indicated that the La3+-doped ZnS nanocrystals (NCs) exhibited a wide visible emission band (blue emission) at room temperature, influenced by the La-doping concentration. Besides, the La3+-doped ZnS QDs elucidated ferromagnetic behavior at room temperature, which may be accredited to the vacancy-assisted bound magnetic polaron model. Exploring the intriguing magnetic features of ZnS: La3+ QDs could open avenues for developing innovative spintronic devices.

Study of Optical, Electrophotographic and Holographic Parameters of As-Se Condensates from the Prehistory of the Original Bulk Materials

The results of a study of the optical, electrophotographic and holographic parameters of As-Se condensates from the prehistory of the original bulk materials are presented. It has been established that the electrophotographic parameters of freshly deposited As40Se60 layers change significantly with temperature; the dependences of the maximum charging potential (U0) and the half-decay time of the potential (τ1/2) of electrophotographic As40Se60 layers in the dark on the processing temperature of the melt of the starting material are shown. The dependence of the half-life of the potential in the dark, as well as the properties of bulk samples, has an extremum in the region of Tsub~500°C. The correlation between the dependences of the properties of bulk samples and the electrophotographic parameters of the layers on Tsub indicates that the structural features of the source material in the deposition mode used affect the structure of the films.

Stretchable Metamaterials with Tunable Infrared Emissivity for Dynamic Thermal Management.

Manipulation of infrared emissivity, which is closely related to surface structure and optical parameters of materials, is a crucial approach for realizing dynamic thermal management. In this study, we design a metamaterial consisting of an array of aluminum disks embedded on a surface of a stretchable elastomeric substrate. Mechanical stretching-induced deformation allows dynamic modification of the surface structure and equivalent optical parameters, thus enabling dynamic control of the emissivity. By utilizing the elastomer polydimethylsiloxane (PDMS) as the substrate, the microstructure interdisk gap can be altered by stretching the PDMS. Through theoretical calculations, the plausibility of this approach is explained by the excitation of plasmon resonance and the variation in the exposed area of highly absorbent PDMS, and the optimal structures for tuning the infrared emissivity are revealed to be 6 μm in diameter and 100 nm in height. Based on this design, we prepare samples with periods of 7 and 7.9 μm and experimentally demonstrate that a change in the period can cause a change in the emissivity and thus tunability in thermal control performance. The temperature difference between the two samples reaches 44.1 °C at a heating power of 0.28 W/cm2 for both samples. Furthermore, we construct a stretching platform that enables in situ mechanical stretching to realize dynamic changes in emissivity. The integral infrared emissivity of the sample increases from 0.32 to 0.5 at a biaxial tensile strain of 13%, achieving a 56% modulation rate of the integral infrared emissivity. The material is expected to enable dynamic thermal management.

Efficacy of orthokeratology lens with the modified small treatment zone on myopia progression and visual quality: a randomized clinical trial

BackgroundTo evaluate the long-term effectiveness of orthokeratology (ortho-K) lenses with small treatment zone (STZ) or conventional treatment zone (CTZ) in controlling axial elongation in children with myopia as well as the impact on visual quality. We also sought to determine the effect of retinal visual signal quality on axial elongation.MethodsThis is a prospective randomized controlled study. A total of 140 participants (age ranging from 8 to 12 years) were randomly assigned to wear either STZ or CTZ ortho-K lenses. STZ ortho-K lenses design was achieved by changing the depth of reverse zone and the sagitta height of the optical zone. Using the IOL-Master 500, axial length (AL) was measured at baseline and after 6, 12 and 18 months of ortho-K treatment. Spherical aberration (SA) and corneal topographic parameters were obtained by the Pentacam anterior segment analyzer at baseline and the 1-month follow-up visit, and optical qualities were assessed by optical quality analysis system-II (OQAS-II) at baseline and after 1 month of lens wearing. Optical quality parameters mainly included the modulation transfer function (MTF) cutoff, Strehl ratio (SR), objective scattering index (OSI), and predicted visual acuity (PVA).ResultsA total of 131 participants completed the study, including 68 in the STZ group and 63 in the CTZ group. The STZ group had significantly reduced AL elongation compared to the CTZ group after treatment (12 months: 0.07 ± 0.11 mm vs. 0.14 ± 0.12 mm, P = 0.002; 18 months: 0.17 ± 0.15 mm vs. 0.26 ± 0.16 mm, P = 0.002). The topography in the STZ group showed a smaller treatment zone (TZ) diameter (2.50 ± 0.23 mm vs. 2.77 ± 0.18 mm, P < 0.001), a wider defocus ring width (2.45 ± 0.28 mm vs. 2.30 ± 0.30 mm, P = 0.006), and larger values of total amount of defocus (119.38 ± 63.71 D·mm2 vs. 91.40 ± 40.83 D·mm2, P = 0.003) and total SA (0.37 ± 0.25 μm vs. 0.25 ± 0.29 μm, P = 0.015), compared with the CTZ group. Objective visual quality decreased in both groups (P < 0.001). This was evidenced by a greater decrease in MTF cutoff (− 14.24 ± 10.48 vs. − 10.74 ± 9.46, P = 0.047) and SR values (− 0.09 ± 0.07 vs. − 0.06 ± 0.07, P = 0.026), and an increase in OSI value (0.84 ± 0.72 vs. 0.58 ± 0.53, P = 0.019). PVA9% decreased significantly in the STZ group but not the CTZ group. A statistically significant negative correlation was found between the changes in total SA and MTF cutoff values (r = − 0.202, P = 0.025). AL changes were associated with sex, change of MTF cutoff value, increment of total SA and TZ area.ConclusionsCompared with CTZ ortho-K lenses, STZ ortho-K lenses significantly inhibited axial elongation in children with myopia while moderately reducing their objective visual quality. Axial elongation was affected by retinal visual quality, and it may be a possible mechanism for ortho-K slowing myopia progression.Trial registration This trial is registered at Chinese Clinical Trial Registry on November 5, 2019 with trial registration number: ChiCTR1900027218. https://www.chictr.org.cn/showproj.html?proj=45380

Optical, AC conductivity and antibacterial activity enhancement of chitosan-silver nanocomposites for optoelectronic and biomedical applications

This study is aimed to prepare and investigate the optical, electrical and antibacterial activity of the environmentally friendly (green) chitosan (Cs)/silver nanocomposites. TEM demonstrated that AgNPs have a spherical shape with particle size ranged from 3 nm to 25 nm. UV analysis spectra of Cs and Cs/Ag nanocomposites showed that, increasing the content of AgNPs led to a noticeable increase in the values of Urbach energy (E U ) and a dramatic decrease in both the indirect (E ig ) and direct (E dg ) optical bandgap energies. It is found that (E ig ) and (E dg ) are decreased from (4.72/5.31 eV) to (2.47/4.19 eV). The formation of the AgNPs is verified by the existence of surface plasmon resonance (SPR) peak at ∼ (421–450) nm. Wemple-DiDomenico and Sellmeier oscillator models are employed and displayed a clear enrichment in the dispersion energy (E d ) and oscillator energy (E 0) as well as the linear and nonlinear optical parameters of Cs. It is observed that the linear (χ(1)) and nonlinear (χ(3) and n2) parameters are enhanced from 0.083, 0.868 × 10−14 and 1.584 × 10−12 to 0.153, 9.762 × 10−14 and 4.088 × 10−12. The novel results in our study nominate Cs/Ag nanocomposites for applications in linear/nonlinear optical devices. AC conductivity behavior of Cs and Cs/Ag nanocomposites is analyzed based on Jonscher’s law and the analysis showed that the overlapping large polaron tunneling (OLPT) is the dominant conduction mechanism for our samples. It is clear that the values of dielectric constant (ε′) of Cs and Cs/Ag nanocomposites are higher confirming the presence of interface polarization (IP) relaxation. Moreover, it is found that the antibacterial activity of Cs against Gram-negative (P. aeruginosa) and Gram-positive (B. thuringiensis) bacteria is found to be enhanced with increasing the content of Ag NPs. These results suggested that Cs/Ag nanocomposites will be good source for preparing bio-nanocomposites for use in many biomedical and industrial applications.

Exploring the optical behavior and relative translucency parameter of CAD-CAM resin-based composites, polymer-infiltrated ceramic network, and feldspar porcelain

ObjectivesTo evaluate and compare the optical properties and relative translucency parameter of CAD-CAM restorative materials. MethodsFour CAD-CAM materials were evaluated: Lava Ultimate (LU), Grandio Blocs (GB), VITA Enamic (VE), and VITA Mark II (VM). Disk-shaped samples in shade A2-HT were prepared (n = 10) and polished to 1.00 ± 0.01 mm of thickness. Scattering (S), absorption (K), albedo (a) coefficient, transmittance (T%), light reflectivity (RI), infinite optical thickness (X∞), and radiative transfer coefficients (μa, and μ′S) were calculated using Kubelka-Munk method and Thennadil's semi-empirical approach. Root Mean Square Error (RMSE) and Goodness of Fit (GFC) were used as performance optical behavior. Translucency differences were evaluated using the relative translucency parameter (RTP00) and 50:50 % translucency perceptibility and acceptability thresholds (TPT00 and TAT00). ResultsThe spectral distribution of S, K, T%, RI, and X∞ was wavelength-dependent. GFC and RMSE values indicated good spectral behavior matches and good comparative spectral values for RI in LU-GB, LU-VE, and GB-VE, and for K in VE-VM. VM displayed the highest scattering values across the wavelengths, while VE and VM showed lower absorption at shorter wavelengths. LU and GB had the highest transmittance. The X∞ values indicated that all 1.0 mm thick materials could be influenced by the background. No good spectral match and no good comparative spectral values were found between CAD-CAM materials and anterior bovine maxillary specimens. VM had the lowest RTP00 values with perceptible and unacceptable differences compared to CAD-CAM materials evaluated. SignificanceUnderstanding the optical behavior of different CAD-CAM materials was essential for guiding clinicians in material selection and optimizing their clinical performance. The findings confirm that the different compositions and microstructure impact the optical properties and translucency of CAD-CAM restorative materials.

The effect of seed layer cycles on the structural, optical, and morphological properties of ZnO nanorods.

In this study, ZnO seed layers with different cycles were formed on glass substrates by the sol-gel technique, and ZnO nanorods were grown on them by the hydrothermal method. Morphology and the structural characterization of the seed films and the ZnO nanorods are carried out by field emission scanning electron microscopy (FE-SEM) and x-ray diffraction techniques. In addition, to investigate the effect of seed layer deposition cycles on the optical properties of the ZnO nanorod arrays, UV/visible spectrophotometer and photoluminescence (PL) measurements were performed. The changes in structural and optical parameters such as dislocation density, strain, crystallite size, and optical band gap values on each seed layer deposition cycle were examined. The highest optical band gap and crystallite size were obtained for ZnO nanorods with 4 cycles seed layer as 3.22 eV and 63.6 nm, respectively. Also, in the PL spectrum, the largest ratio of UV-emission region to weak-visible emission region was obtained in ZnO nanorods having 4 cycles. In addition, the glucose detection properties of ZnO nanorods having 4 cycles were investigated using the PL measurements and it was found that UV-emission peak intensity of ZnO nanorods decreased as the glucose concentration increased from 8 to 40 mM. The results show that the number of deposition cycles of the seed layer has a strong influence on the orientation, crystal quality, and optical band gap of the growing ZnO nanorods, as well as significantly affecting their morphological properties. RESEARCH HIGHLIGHTS: High quality ZnO nanorods were grown on glass substrates by hydrothermal method. The effect of ZnO seed layer cycles on the structural, optical, and morphological characteristics of ZnO nanorods grown on were examined. It was found that the number of cycles of the seed layer is a critical parameter for growing quality and well-aligned ZnO nanorods.

Exploring the structural, electronic, mechanical, magnetic and optical properties of Cs-based hydride-perovskites CsXH3 (X = Cr, Mn) for hydrogen storage application

Low cast hydride-perovskites are more efficient in power conversion and for energy storage. Here in, structural investigation, electronic, mechanical and optical properties of hydrogen based CsXH3 (X = Cr, Mn) compounds using the density functional theory. The result shows that both materials crystallize into cubic structure. The thermodynamic and dynamic stabilities are conformed through formation energy and phonon dispersion curve. The optimized lattice constants are 3.52 Å and 3.54 Å for CsCrH3 and CsMnH3 respectively. Both materials are found to be half metallic in nature. IR-Elast package are used to obtain elastic constants. The elastic study presents that both materials are ductile and have anisotropic nature. The optical parameters are studied in the range of 0–10 eV. The optical results show that both materials have an excellent optical absorption. The values obtained of gravimetric hydrogen storage capacity for these compounds are 1.55 % and 1.58 % for CsMnH3 and CsCrH3 respectively indicating that these materials can be an excellent candidate for hydrogen energy storage.

Blue and white light emissions and energy transfer in Tm3+ and Dy3+/Tm3+ doped lithium-aluminum-zinc phosphate glasses

Lithium-aluminum-zinc phosphate glasses doped with thulium and dysprosium ions are characterized by using spectroscopy techniques. The Judd-Ofelt parameters were evaluated to calculate the radiative parameters of thulium 1D23F4 and 1G43H6 visible transitions and 3H43F4 near infrared transition, which shows the highest optical amplification parameters. Upon 356 nm excitation, the Tm3+ doped phosphate glass emits blue light with CIE1931 chromaticity coordinates x = 0.1540 and y = 0.0283 and color purity around 96.8%. With excitations at 347 and 350 nm, the Dy3+/Tm3+ doped phosphate glass emits neutral and cold white light with correlated color temperature values of 4716 and 6628 K, respectively. The dysprosium emission decay time in the codoped glass is shorter than that in the Dy3+ single-doped glass, indicating a non-radiative energy transfer from Dy3+ to Tm3+. The dominant electrical interaction involved in the energy transfer, following the model Inokuti-Hirayama, is of dipole-dipole type. The energy transfer probability and efficiency are 769.0 s-1 and 0.53, respectively. Tm3+ doped and Dy3+/Tm3+co-doped lithium-aluminum-zinc phosphate glasses could be appropriate for blue and neutral/cold white light-emitting device applications.

The effect of oxygen vacancies on the optical and thermophysical properties of (1-x)Si3N4 – xAl2O3 ceramics

Interest in composite ceramics based on silicon nitride (Si3N4) and aluminum oxide (Al2O3) is due to the possibility of using them as semiconductor applications associated with their operation under conditions of external influences, including heating. The paper presents the results of assessing the influence of variations in the phase composition of (1-x)Si3N4 – xAl2O3 ceramics on alterations in optical and thermophysical parameters, as well as their relationships. Analysis of the optical characteristics of the ceramics under study showed that changes in the phase composition associated with the dominance of the Al2O3 phase in the composition of the ceramics lead to a change in covalent bonds and an increase in the number of ionic bonds, which also affects the change in the semiconductor nature of the ceramics, and therefore, a change in the thermophysical properties. According to the assessment of changes in the thermal conductivity coefficient of the studied ceramics, with the dominance of the Al2O3 phase in the composition, the observed growth in the concentration of structural defects, as well as oxygen vacancies, results in the thermal conductivity coefficient decrease, as well as an elevation in the thermal expansion of ceramics during thermal heating. It has been determined that the presence of a combination of Al2(SiO4)O and Si3N4 phases in the ceramic composition leads to an increase in the thermal conductivity coefficient, as well as maintaining its stability over a wide temperature range.

Impact of Pd2+ and Sn4+ co-doping ZnO nanoflakes toward high-performing Schottky diode based on the generation of intermediate bands within the energy gap

Pd:Sn/ZnO nanohybrid was prepared by chemical co-precipitation route and identified using XRD, EDX, SEM, and TEM techniques. The microstructure analysis emphasized the polycrystalline nature in which Pd and Sn ions were substituted inside ZnO framework to form the nanocomposite. The surface morphology was appeared in 2D nanoflakes with large specific surface area. The optical parameters including Eg, n, and k were deduced from T% and R% spectra through wavelength range 300–1400 nm. The thin film showed strong optical absorption inside the UV region with a value of Eg = 3.10 eV. The Ag/Pd:Sn/ZnO/p-Si/Al Schottky diode was fabricated by thermal evaporation technique, and its electronic and photodetector properties were investigated from I–V and C–V measurements. The fabricated device exhibited non-ideal behavior with high rectification ratio RR = 935 and a relatively small Rs lies between 2365 and 2755 Ω. Under illumination impacts, the photodiode exhibited high photosensitivity and responsivity attributed to the large photo-induced charge carriers.

Detecting changes in anthropogenic light emissions: Limits due to atmospheric variability

Monitoring the evolution of the anthropogenic light emissions is a priority task in light pollution research. Among the complementary approaches that can be adopted to achieve this goal stand out those based on measuring the direct radiance of the sources at ground level or from low Earth orbit satellites, and on measuring the scattered radiance (known as artificial night sky brightness or skyglow) using networks of ground-based sensors. The terrestrial atmosphere is a variable medium interposed between the sources and the measuring instruments, and the fluctuation of its optical parameters sets a lower limit for the actual source emission changes that can be confidently detected. In this paper we analyze the effect of the fluctuations of the molecular and aerosol optical depths. It is shown that for reliably detecting changes in the anthropogenic light emissions of order ∼1 % per year, the inter-annual variability of the annual means of these atmospheric parameters in the measurement datasets must be carefully controlled or efficiently corrected for.

Insights and perspectives on PVDF/MgO NCs films: Structural and optical properties for optoelectronic device applications

In the current investigation, pure polyvinylidene fluoride (PVDF) and PVDF-MgO nanocomposite (NC) thin films are fabricated via solvent casting method using PVDF as a polymer matrix with different proportions of magnesium oxide (MgO) (0.5–2 wt%). The structural, morphological and optical properties of the prepared polymer NCs are studied by using XRD, FTIR, SEM, Raman and UV–Vis spectroscopy techniques. The α and β phases are detected in XRD measurements. MgO powder peaks are in good agreement with the reported literatures. The average crystallite size, lattice strain, and dislocation density of the prepared thin films are estimted by using Williamson-Hall (W-H) plot. SEM micrographs reveals the fluorine-containing carbon chain network that forms the spherulite and fiber-like structure in the PVDF/MgO NCs films. The Raman and FTIR spectra of PVDF/MgO and pure PVDF films are also evaluated. UV–Vis spectroscopy is used to examine the absorbance, transmittance, and reflectance spectra of pure PVDF and PVDF/MgO NCs thin films. The dipole polarization interaction causes the absorption coefficient, direct band gap, indirect band gap, optical activation energy, and skin depth of pure PVDF and PVDF/MgO thin films to decrease, whereas increasing the dielectric constant at high frequency value, refractive index, loss, optical conductivity, and dielectric constant per effective mass of NCs films. Optical dispersion parameters are estimated by the single oscillator model. The obtained results can be employed in the possible applications in supercapacitors. The method used for the preparation of thin films are inexpensive and eco-friendly.

First-Principles insights to probe structural and opto-electronic properties of [formula omitted] (Y=Mg, Sr) halide perovskites with variety of DFT methods

This study reports the structural, electronic, optical, phonon, thermodynamic and thermoelectric properties of AgYF3 (X=Mg, Sr) for photovoltaic and energy applications. We performed first principles calculations using full potential linearized augmented plane wave, FP-LAPW method implemented in Wien2k. The generalized gradient approximations of Perdew–Burke–Ernzerhof PBE-GGA, and PBE revised for solids, PBEsol, is employed for structural optimization of these lead free halide perovskites. The Birch–Murnaghan energy volume curve fitting comprehend the structural stability. The optimized lattice constant of AgMgF3 and AgSrF3 obtained with PBE-GGA(PBEsol) is 3.99(3.92)Å and 4.42(4.65)Å. The stability is further tested with the help of formation energy and positive phonon dispersion curves calculations. For the calculations of explicit electronic and optical properties, we also employed Tran–Blaha modified Beck–Johnson (TB-mBJ) and Strongly Constrained but Appropriately Normed, SCAN, exchange and correlations functionals. The electronic band gap of AgMgF3 computed with PBEsol, TB-mBJ and SCAN is 1.96 eV, 5.25 eV and 2.59 eV exhibiting M-Γ indirect band gap. The band gap energy of AgSrF3 is 2.06 eV, 6.42 eV and 2.70 eV with PBEsol, TB-mBJ and SCAN. The indirect band gap nature of AgSrF3 is confirmed by PBEsol and TB-mBJ while it anticipated direct band gap behavior with meta-GGA SCAN. The different optical parameters like dielectric constant, optical conductivity, energy loss function, absorption, reflectivity and refractive index are calculated to assess optical activity of both perovskites. Comprehensive electronic and optical analysis advocates the utility of AgMgF3 and AgSrF3 for different applications is solar technology and optoelectronic devices.

Theoretical simulation study of laser-induced plasma bombardment on bacteria

With the rapid advancement of laser decontamination technology and growing awareness of microbial hazards, it becomes crucial to employ theoretical model to simulate and evaluate decontamination processes by laser-induced plasma. This study employs a two-dimensional axisymmetric fluid dynamics model to simulate the power density of plasma bombardment on bacteria and access its decontamination effects. The model considers the transport processes of vapor plasma and background gas molecules. Based on the destructive impact of high-speed moving particles in the plasma on bacteria, we investigate the bombardment power density under various conditions, including different laser spot sizes, wavelengths, plate’s tilt angles, and plate-target spacing. The results reveal that the bombardment power density increases with a decrease in laser spot size and wavelength. For instance, when the plate is parallel to the target surface with a 1 mm spacing, the bombardment power density triples as the laser spot size decreases from 0.8 mm to 0.5 mm and quadruples as the wavelength decreases from 1064 nm to 266 nm. Notably, when the plate is parallel to the target with a relatively close spacing of 0.5 mm, the bombardment power density at 0° inclination increases sevenfold compared to 45°. This simulation study is essential for optimizing optical parameters and designing component layouts in decontamination devices using laser-induced plasma. The reduction of laser spot size, wavelength, plate-target spacing and aligning the plate parallel to the target, collectively contribute to achieving precise and effective decontamination.

A virtual visualization method for improving the manufacturing accuracy based VPP 3D printers

Compared to traditional vat photopolymerization 3D printing methods, pixel blending technique provides greater freedom in terms of user-defined lighting sources. Based on this technology, scientists have conducted research on 3D printing manufacturing for elastic materials, biologically inert materials, and materials with high transparency, making significant contributions to the fields of portable healthcare and specialty material processing. However, there has been a lack of a universal and simple algorithm to facilitate low-cost printing experiments for researchers not in the 3D printing industry. Here, we propose a mathematical approach based on morphology to simulate the light dose distribution and virtual visualization of parts produced using grayscale mask vat photopolymerization 3D printing technology. Based on this simulation, we develop an auto-correction method inspired by circle packing to modify the grayscale values of projection images, thereby improving the dimensional accuracy of printed devices. This method can significantly improve printing accuracy with just a single parameter adjustment. We conducted experimental validation of this method on a vat photopolymerization printer using common commercial resins, demonstrating its feasibility for printing high precision structures. The parameters utilized in this method are comparatively simpler to acquire compared to conventional techniques for obtaining optical parameters. For researchers in non-vat photopolymerization 3D printing industry, it is relatively user-friendly.

Effects of MoO3 on the structural, physical, mechanical, optical, and ionizing shielding of borate-germanate-telluride glass system

In this investigation, a group of different concentrations of molybdenum trioxide-doped borate-germanate-telluride glasses have been synthesized. Four glasses with a composition formula of (35-x) B2O3-20TeO2-10GeO2-35MgO-xMoO3 where x values vary between 5 and 20 mol % have been achieved using the melt-annealing process. X-ray diffraction for the current M1 sample was utilized to prove the glassy nature. FTIR has been measured to understand the glass structure. Many functional group and vibrational bonds were observed. The optical parameters for B2O3-TeO2-GeO2-MgO-MoO3 glass samples were calculated based on absorption spectra recorded in the 200–1100 nm wavelength range. The optical electronegativity (χ) and optical basicity (Λ) were calculated as critical parameters that can be used to evaluate the glass structure. Physical parameters like density, molar volume (Vm), packing density (Vt), oxygen packing density (OPD), and oxygen molar volume (OMV) were measured and calculated. Hardness (H), Poisson ratio (σ), Fractal bond conductivity (d), and elastic moduli of M1, M2, M3, and M4 glass samples were calculated. Mass attenuation coefficients (MAC) for four synthesized glass samples were reported along with linear attenuation coefficient (LAC) as a function of photon energy. Based on the transmission factor TF %, it shows extremely low percentages at the lowest energy region, dropping to less than 1 % at 0.015 MeV up to 0.08 MeV in all samples. The radiation protection efficiency (RPE) was examined to measure the samples' capacity to attenuate ionizing radiation.

Insight into deposition duration-varied crystallinity, optical parameters, morphology and electrical properties of solution-processed nanostructured CdSSe thin films

Nanostructured cadmium sulpho selenide (CdSSe) films have been grown onto glass substrates for different deposition durations via a facile solution-based method known as chemical bath deposition (CBD). XRD studies revealed that the crystallites in the films possessed hexagonal (wurtzite) structures with predominant orientation along the (002) plane. The crystallite size increased from ∼5.95 nm to ∼16.69 nm with the increase in deposition duration from 1 h to 4 h. The absorbance, transmittance and reflectance measurements were carried out. A transparency of ∼(50–80) % was obtained for the films. The direct optical energy band gap was found to decrease from 1.982 eV to 1.952 eV with the increment of deposition duration from 1 h to 4 h. SEM micrographs of the films revealed the presence of nano spherical-shaped grains with an average size ranging from ∼305 nm to ∼612 nm. HRTEM images illustrated the presence of compact nano-spherical grains and nano-crystallites distributed in random orientations. Raman spectroscopy divulged the presence of CdSe and CdS vibrational Raman modes and overtones in the films. PL spectra revealed a prominent red emission band along with weak luminescent bands in the yellow-red emission region. The presence of Cd–Se and Cd–S bonds in the films was validated using FTIR analysis. Electrical investigation revealed the linear current‒voltage relationship for the films with the rise in conductivity with deposition duration. Hence, deposition duration stands out as a vital parameter for modulating the properties of CdSSe thin films for use in photovoltaic devices and optoelectronics.

Insights into Ag2Mo3SeO12 for photovoltaic and optoelectronic applications: A theoretical exploration of its structural, electronic, and thermoelectric behavior

The theoretical investigation of the newly discovered quadruple perovskite Ag₂Mo₃SeO₁₂ was conducted using density functional theory (DFT) with the generalized gradient approximation (GGA-PBE) for the structural properties. This study examined the compound's structural, electronic, optical, and thermoelectric properties, utilizing the Tran Blaha modified Becke-Johnson exchange potential (mBJ) for accurate band gap measurement to overcome the bandgap underestimation by GGA-PBE. The stable structure was confirmed through energy-volume optimization and fitted with the Birch-Murnaghan equation of state, using PBE-GGA exchange correlation functional. The findings revealed a band structure with direct transition under the TB-mBJ approach with an energy gap of 1.45 eV. Detailed analyses were conducted, including the density of states and charge density distribution maps. Various optical parameters such as the dielectric function, absorption coefficient, refractive index, and reflectivity were computed, with the static dielectric constant measured at 6.3. Notably, a significant evolution of the absorption coefficient in the visible region highlights the potential of Ag₂Mo₃SeO₁₂ for solar cell and optoelectronic applications. These results pave the way for new photovoltaic material designs. Furthermore, the material demonstrates promising thermoelectric properties with an appropriate figure of merit, Seebeck coefficient, and electrical and thermal conductivity evolution under different temperature conditions, indicating its potential for photovoltaic and optoelectronic applications.

DFT insight into the phase stability, optoelectronic, elastic, vibrational, and thermodynamic properties of metal chalcogenides RbKM (M = S, Se, Te) for energy harvesting technology

In this manuscript, the structural, optoelectronic, elastic, vibrational, and thermodynamic properties of RbKM (M = S, Se, Te) chalcogenides are explored via first principles approach. The estimated equilibrium lattice parameters a(c) through the TB-mBJ functional are 5.3876 Å (8.2810 Å), 5.2700 Å (8.6550 Å) and 5.2656 Å (8.7707 Å) for RbKS, RbKSe and RbKTe, respectively. The large value of the cohesive (Ecoh) and formation energy (Eform) reveals that all these compounds are stable at 0 K that may be difficult to decompose at ambient conditions. The direct band gap for RbKS, RbKSe and RbKTe is noted as 4.05 eV, 3.71 eV and 3.63 eV, respectively that is sufficient to declare them as semiconducting materials. So far as, the projected density of states (PDOS), pseudo electrons residing in d orbitals of the rubidium atoms contribute in the conduction region and p orbitals of chalcogen elements partake in the valence band. The optical parameters are determined by Kramers-Kronig relations. The elastic constants unveil that all compounds are mechanically stable and hold anisotropic nature. Here the vibrational properties of RbKM (M = S, Se, Te) are examined through Density functional perturbation theory (DFPT) technique. The Harmonic Approximation Method (HAM) is utilized to seek thermodynamic stability that is ensured due to the observance of negative free energy for all cases. Our theoretical outcomes for RbKM (M = S, Se, Te) can contribute significantly to amelioration for future research in devising optoelectronic and energy harvesting like appliances.