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The bright side of PV production in snow-covered mountains
摘要： Our work explores the prospect of bringing the temporal production profile of solar photovoltaics (PV) into better correlation with typical electricity consumption patterns in the midlatitudes. To do so, we quantify the potential of three choices for PV installations that increase production during the winter months when electricity is most needed. These are placements that favor (i) high winter irradiance, (ii) high ground-reflected radiation, and (iii) steeper-than-usual panel tilt angles. In addition to spatial estimates of the production potential, we compare the performance of different PV placement scenarios in urban and mountain environments for the country of Switzerland. The results show that the energy deficit in a future fully renewable production from wind power, hydropower, and geothermal power could be significantly reduced when solar PV is installed at high elevations. Because the temporal production patterns match the typical demand more closely than the production in urban environments, electricity production could be shifted from summer to winter without reducing the annual total production. Such mountain installations require significantly less surface area and, combined with steeper panel tilt angles, up to 50% of the winter deficit in electricity production can be mediated.
关键词： panel tilt,seasonal energy gap,renewable energy,photovoltaic,surface reflectance
更新于2025-09-23 15:23:52
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Inverse logarithmic derivative method for determining the energy gap and the type of electron transitions as an alternative to the Tauc method
摘要： We present a method derived from Mott and Davies or Cody equation for calculating energy gap based on spectrophotometric measurements. The method has been tested on thin film TiO2 and MoS2/TiO2 bilayer produced by RF magnetron sputtering. The presented examples indicate that the Tauc and McLean methods, which are usually used to analyse data, are not justified in many cases, especially for multilayers. In the Tauc method, the problem is to determine the energy gap without knowing the nature of the optical transition. The McLean method involves fitting the power function which may cause difficulties in the proper selection of the fitting range. The presented method is based on the transformation of measurement data using inverse logarithmic derivative and performing of linear fittings. Our method does not assume value of the parameter m describing the nature of the optical transition and does not require knowledge of the thickness of the layers. The value of energy gap and parameter m can be obtained simultaneously thanks to one linear fit. In addition, this method has a practical advantages over methods of McLean and Tauc, which are described in the article.
关键词： Tauc equation,Cody equation,Optical transitions,Energy gap,Multilayer
更新于2025-09-23 15:23:52
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Structural, photoluminescence and magnetic properties of Cu-doped SnO2 nanoparticles co-doped with Co
摘要： Co doped Sn0.98Cu0.02O2 nanoparticles have been synthesized by co-precipitation method. The prepared nanoparticles were characterized by X-ray diffraction, scanning electron microscope (SEM), transmission electron microscopy, Fourier transform infrared spectroscopy, photoluminescence and magnetic measurements. The observed tetragonal rutile structure confirmed by XRD patterns was not altered by Co-doping and the value of average crystallite size lies within 8–14 nm. The formation of high density defect states and the new phases of Co and Sn were responsible for the reduction of energy gap (Eg) with Co-doping; Eg varied between 3.12 and 3.58 eV. The tuning of band gap and luminescence properties by Co-doping suggested that Co = 4% doped sample is a promising material for selective coatings for solar cells; use as antireflective coating materials, and for fabrication of optoelectronic devices. FTIR spectrum has been used to authenticate the formation of Sn–O bond and the existence of Co in Sn–Cu–O. The promotion of higher local disorders and the oxygen-related defects during growth process of SnO2 nanoparticles at Co = 4% is responsible for the higher UV/violet/blue band photoluminescence emission intensity. The overlapping between bound magnetic polarons (BMP) by Co-doping induced the room temperature ferromagnetism. The existence of high density charge carriers and oxygen vacancies at Co = 4% sample might be responsible for highest magnitude of ferromagnetism. The noticed suppression of RTFM at Co = 6% may be due to the enhanced antiferromagnetic interaction between neighbouring Co–Co ion.
关键词： Photoluminescence,SnO2 nanoparticles,XRD,Energy gap,Magnetic properties
更新于2025-09-23 15:23:52
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Temperature effect on structural, optical and NH<SUB align="right">3 gas sensing properties of TeO<SUB align="right">2 thin films
摘要： TeO2 thin films with different temperatures (400, 450 and 500°C) were deposited on glass substrates by thermal evaporation technique from a Te powder. XRD patterns indicate that as the temperature increases, the crystallisation improves. Observing the images obtained by SEM, it is seen that the grain size decreases as the temperature increases. The optical energy gap of the films was determined from transmittance and reflectance spectra. The optical energy gap decreased continuously from 3.95 eV to 3.80 eV with increasing temperature. Studying the effect of deposition temperature on NH3 gas measurement, it became obvious that as the deposition temperature increases, the sensitivity increases and the response and recovery times decrease.
关键词： scanning electron microscope,XRD,thin films,sensitivity,X-ray diffraction,energy gap,SEM,optical
更新于2025-09-23 15:22:29
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Decreased Energy Gap and Enhanced Conductivity in Zn-Doped Sr2IrO4
摘要： The 5d transition metal oxide Sr2IrO4 has attracted much interest in the high-temperature superconductivity community since it highly resembles the cuprate superconductor in crystal and electronic structures. Here, we report on the transport and magnetic properties of Zn-doped Sr2IrO4. It is found that the energy gap of Sr2IrO4 is rapidly decreased with a small amount of Zn doping. Consequently, the electrical conductivity is significantly enhanced. The present work could serve as the prerequisite stage in exploring the possible superconductivity of the Sr2IrO4 compound.
关键词： Energy gap,Magnetic moment,Sr2IrO4
更新于2025-09-23 15:22:29
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The influence of yttrium-ions on the optical and electrical behavior of PVA polymeric films
摘要： The polyvinyl alcohol (PVA) films doped with various wt% of yttrium nitrate salt were synthesized by standard solution casting technique in order to examine the functional electrical and optical properties. The degree of the crystalline structure that evaluated in the films were investigated by x-ray diffraction and Fourier transform infrared spectroscopy measurements. In addition, the surface images have been obtained via scanning electron microscopy (SEM). The optical parameters have been calculated from UV–visible-NIR transmittance spectroscopy. Also, the dielectric constant measurement and the DC resistance that are arisen in the PVA films with different wt% of Y3+ have been done. All the samples show semi-crystalline phases. The average size, of the cluster Y3+ in the SEM images, increase to 1.63 μm for PVA/37 wt% Y3+ sample. Therefore, the optical absorption of this sample is higher than the others. The value of the energy gap decrease from 5.11 eV to 4.47 eV for PVA/0.037 wt% Y3+ and PVA/37 wt% Y3+ samples, respectively. The nonlinear current—voltage behavior, at high applied voltage, of the polymeric films, is observed with different values of slope, which is a characteristic of the varistor materials. So, these films could be used in different applications like optoelectronic and varistor devices.
关键词： Varistor,Dielectric,XRD/FTIR,SEM,Optical energy gap,Y3+-doped PVA
更新于2025-09-23 15:22:29
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Accurate Gap Determination in Monolayer and Bilayer Graphene/h-BN Moiré Superlattices
摘要： High mobility single and few-layer graphene sheets are in many ways attractive as nanoelectronic circuit hosts but lack energy gaps, which are essential to the operation of field-effect transistors. One of the methods used to create gaps in the spectrum of graphene systems is to form long period moiré patterns by aligning the graphene and hexagonal boron nitride (h-BN) substrate lattices. Here, we use planar tunneling devices with thin h-BN barriers to obtain direct and accurate tunneling spectroscopy measurements of the energy gaps in single- and bi-layer graphene-h-BN superlattice structures at charge neutrality (first Dirac point) and at integer moiré band occupancies (second Dirac point, SDP) as a function of external electric and magnetic fields and the interface twist angle. In single-layer graphene we find, in agreement with previous work, that gaps are formed at neutrality and at the hole-doped SDP, but not at the electron-doped SDP. Both primary and secondary gaps can be determined accurately by extrapolating Landau fan patterns to zero magnetic field and are as large as ≈ 17 meV for devices in near perfect alignment. For bilayer graphene, we find that gaps occur only at charge neutrality where they can be modified by an external electric field.
关键词： graphene-h-BN moiré superlattice,Landau level tunneling spectroscopy,bilayer graphene-h-BN superstructure,high-precision measurement,graphene energy gap
更新于2025-09-23 15:21:21
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Profound optical analysis for novel amorphous Cu2FeSnS4 thin films as an absorber layer for thin film solar cells
摘要： In this study, quaternary kesterite Cu2FeSnS4 (CFTS4) has been selected due to its interesting optical and electrical characteristics. The CFTS4 films were prepared by exploiting the chemical bath deposition process at room temperature. The films were prepared at different deposition periods (1, 3, 5 and 7 h). The EDAX technique was helped in evaluating the compositional element ratio which near to 2:1:1:4. The morphology and structure of CFTS4 films have been examined by utilizing X-ray diffraction, and field emission scanning electron microscope techniques. XRD charts revealed the absence of sharp peaks and approved the amorphous nature of films under investigations. The transmittance and reflectance data were employed to compute the linear and nonlinear optical constants of the as-deposited CFTS4 films. The energy gap calculations for the CFTS4 films grown on glass substrate displayed a direct energy gap and by increasing the deposition time, a reduction in energy gap values from 1.41 to 1.19 eV was obtained. The deep analysis of linear/nonlinear optical properties as a function of deposition time has revealed many characteristics of the investigated films. Moreover, the nonlinear parameters (refractive index n2, nonlinear absorption coefficient βc and the third-order nonlinear optical susceptibility χ(3)) of the CFTS4 films were boosted with rising up the film thickness and their high values imply the possibility of utilizing these films in various optoelectronic applications.
关键词： Optical conductivity,Energy gap,Optoelectronic applications,Chemical bath deposition technique,CFTS4 thin films
更新于2025-09-23 15:21:01
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Electronic structure and transport properties of graphene/h-BN controlled by boundary potential and magnetic field
摘要： We study the band structure of the lattice-matched graphene/h-BN bilayer system in the most stable configuration. An effective way to individually manipulate the edge state by the boundary potentials is proposed. It is shown that the boundary potential can not only shift and deform the edge bands, but also modify the energy gap. We also explore the transport properties of graphene/h-BN under a magnetic field. The boundary potential can change the distribution of the edge states, resulting in an interesting evolution of the quantized conductance.
关键词： energy gap,transport property,Lattice-matched graphene/h-BN,boundary potential
更新于2025-09-23 15:21:01
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Luminescence of Phosphate Glasses: P2O5-ZnO-BaF2-K2TeO3-Al2O3-Nb2O5 Doped with Sm3+ Ions for Display and Laser Material
摘要： Luminescent phosphate glasses having the composition 40P2O5-30ZnO-20BaF2-3.8K2TeO3-1.2Al2O3-5Nb2O5 in mol.% doped with 3 9 103 ppm and 4 9 103 ppm Sm2O3 were successfully prepared by a melt-quenching technique. The investigated glasses were characterized by x-ray diffraction, UV–visible–NIR, absorption, emission, and ?uorescence lifetime analysis. The radiative properties were calculated using Judd–Ofelt (J–O) spectral intensity parameters for each of the glasses, which revealed the following trend: X2 > X4 > X6. The J–O intensity parameters were used to evaluate the spontaneous emission properties including branching ratios, transition probabilities, and radiative lifetime. The value of the optical energy band gap was found to decrease with an increase in Sm3+ content, which is explained on the basis of structural changes. The calculated stimulated emission cross-section studied was high, and increased from rSE; at 1.62 lm of glasses 3.81 9 10(cid:2)21 cm2 to 4.38 9 10(cid:2)21 cm2 with increasing Sm3+ ion concentration. The structure of the glasses was investigated by computing Internuclear (cid:3) and ?eld strength F( ) and measurement of Raman spectra.
关键词： refractive index,UV–Vis–NIR,Judd–Ofelt analysis,emission cross-section,Raman spectra,Oxide glasses,density,optical energy gap
更新于2025-09-23 15:21:01