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Electric Field Controlled Indirect-Direct-Indirect Band Gap Transition in Monolayer InSe
摘要： Electronic structures of monolayer InSe with a perpendicular electric field are investigated. Indirect-direct-indirect band gap transition is found in monolayer InSe as the electric field strength is increased continuously. Meanwhile, the global band gap is suppressed gradually to zero, indicating that semiconductor-metal transformation happens. The underlying mechanisms are revealed by analyzing both the orbital contributions to energy band and evolution of band edges. These findings may not only facilitate our further understanding of electronic characteristics of layered group III-VI semiconductors, but also provide useful guidance for designing optoelectronic devices.
关键词： Monolayer InSe,Electric field,Indirect-direct-indirect band gap transition
更新于2025-09-16 10:30:52
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Europium-doped boro-telluro-dolomite glasses for red laser applications: Basic insight into spectroscopic traits
摘要： Naturally abundant minerals and lanthanide-doped synthetic boro-tellurite networks have become prospective efficient laser hosts because of the synergy between them. Driven by this idea, Eu3+-doped boro-telluro-dolomite (BTD) glasses were prepared via the melt-quenching method. The spectroscopic traits of as-quenched samples were analyzed though experimental and theoretical studies. The result from the derivation of absorption spectral fitting (DASF) model demonstrated the direct allowed transition in the glasses. Moreover, the photo-luminescence spectra of the sample containing 1.0 mol% of Eu3+ (BTD1.0Eu glass) revealed a prominent red peak at 611 nm (assigned to 5D0 → 7F2 transition in Eu3+ ion) with a large stimulated emission cross section (7.15 × 10?22 cm2) and a high luminescence branching ratio (61.5%). Furthermore, the attained CIE color coordinates (0.637, 0.363), which lie near the standard red hue (0.67, 0.33), together with high quantum efficiency (92.7%) affirmed the effectiveness of BTD1.0Eu glass as a potential red laser host.
关键词： Boro-telluro-dolomite glasses,Red emission,Europium ions,Judd–ofelt analysis,Radiative parameter,Optical band-gap energy
更新于2025-09-16 10:30:52
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Direct Z-scheme photocatalytic removal of ammonia via the narrow band gap MoS2/N-doped graphene hybrid catalyst upon near-infrared irradiation
摘要： Near-infrared (NIR) irradiation accounts for approximately 54.3% of the solar spectrum. Therefore, MoS2 and N-doped graphene (NG) were utilised to fabricate a direct Z-scheme NIR-response photocatalytic system (MoS2/NG). The photocatalytic tests showed that MoS2/NG Z-scheme photocatalytic system can result in a 99.6% degradation ratio of ammonia under NIR irradiation, whereas the removal ratio of ammonia was only 64.0% using MoS2 as the photocatalyst under similar conditions. The catalytic e?ciency is still over 90.7% even if the MoS2/NG catalyst was used for ?ve runs, indicating that it is extremely stable. The kinetic research indicated the ?1. The average apparent rate constant kapp for ammonia degradation into N2 was at approximately 0.251 h enhanced photocatalytic activity of MoS2/NG was attributed to the more positive valence band level of the Z-scheme system.
关键词： MoS2/N-doped graphene,Near-infrared irradiation,Degradation ammonia,Narrow band gap,Z-scheme photocatalysis
更新于2025-09-12 10:27:22
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Magneto-Optical Isolator Based on Ultra-Wideband Photonic Crystals Waveguide for 5G Communication System
摘要： This paper presents a novel magneto-optical isolator based on an ultra-wideband and high efficiency photonic crystals (PCs) waveguide and gyromagnetic ferrites. The three-dimensional numerical simulation finds that the photonic crystals waveguide’s (PCW) transmission efficiency rises with its height and width. The corresponding experiments are performed by using a triangular lattice Al2O3 dielectric posts array in 5G millimeter wave band. The measured transmission efficiency is up to 90.78% for the optimal PCs waveguide structure, which has ultra-wide operating bandwidth from 23.45 to 31.25 GHz. The magneto-optical isolator is designed by inserting two rectangular gyromagnetic ferrites into the PCs waveguide. Due to the contrast between the effective permeability of the left and right circular polarization waves passing through the magnetized ferrite sheets, the ferromagnetic resonance absorption of the forward and reverse waves is different. By using finite element method, the isolation is optimized to be 49.49 dB for the isolator and its relative bandwidth reaches 8.85%. The high isolation, broadband, and easy integration indicate that our designed magneto-optical isolator has significant advantage in 5G communication systems.
关键词： photonic crystals waveguides,magneto-photonic isolator,wideband,5G communication,photonic band gap
更新于2025-09-12 10:27:22
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Molecular Engineering on Bis(Benzothiophene-S,S-Dioxide)-Based Large Band-Gap Polymers for Interfacial Modifications in Polymer Solar Cells
摘要： The development of effectively universal interfacial materials for both conventional and inverted polymer solar cells (PSCs) plays a very crucial role in achieving highly photovoltaic performance and feasible device engineering. In this study, two novel alcohol-soluble conjugated polymers (PBSON-P and PBSON-FEO) with bis(benzothiophene-S,S-dioxide)-fused aromatics (FBTO) as core unit and amino as functional groups are synthesized. They are utilized as universal cathode interfacial layers for both conventional and inverted PSCs simultaneously. Ascribing to the enlarged conjugated planarity and higher electron affinity for FBTO unit, both of PBSON-P and PBSON-FEO exhibit versatile electron-transporting abilities. They show wide band gaps that are important for light absorption in inverted PSCs, at which point PBSON-P and PBSON-FEO are more progressive than some of the reported small band-gap cathode interfacial materials. Importantly, PBSON-P and PBSON-FEO display deep HOMO energy levels, which can block holes at the cathode and thus increase fill factor. As a result, both of conventional and inverted PSCs using PBSON-P and PBSON-FEO as cathode interlayers realize high photovoltaic performance. Therefore, this series of novel polymers are amphibious cathode interfacial materials for high-performance conventional and inverted PSCs.
关键词： amino,cathode interfacial layers,large band-gap polymers,benzothiophene-S,S-dioxide,polymer solar cells
更新于2025-09-12 10:27:22
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Laser irradiation-induced structural, microstructural and optical properties change in Bi-doped As <sub/>40</sub> Se <sub/>60</sub> thin films
摘要： The laser irradiation of thermally evaporated As40Se55Bi5 and As40Se45Bi15 thin films was found to be accompanied by structural changes which in turn changed the optical constant. The thin films under investigation were characterized by the X-ray diffraction method to study the structural change and the surface morphology was checked by field emission scanning electron microscope. The composition of the films was verified from the energy dispersive X-ray analysis. The changes in optical properties due to the influence of laser irradiation were calculated from the transmission spectrum recorded by UV–Visible spectrometer in the wavelength region 400–1200 nm. The decrease in optical band gap (photodarkening) is explained on the basis of density of state model proposed by Mott–Davis. The Raman analysis showed the Raman shift and symmetric stretching vibration of As–Se.
关键词： thin films,optical properties,optical band gap,Chalcogenides,laser irradiation
更新于2025-09-12 10:27:22
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All-Optical Ultra-Fast Graphene-Photonic Crystal Switch
摘要： In this paper, an all-optical photonic crystal-based switch containing a graphene resonant ring has been presented. The structure has been composed of 15 × 15 silicon rods for a fundamental lattice. Then, a resonant ring including 9 thick silicon rods and 24 graphene-SiO2 rods was placed between two waveguides. The thick rods with a radius of 0.41a in the form of a 3 × 3 lattice were placed at the center of the ring. Graphene-SiO2 rods with a radius of 0.2a were assumed around the thick rods. These rods were made of the graphene monolayers which were separated by SiO2 disks. The size of the structure was about 70 μm2 that was more compact than other works. Furthermore, the rise and fall times were obtained by 0.3 ps and 0.4 ps, respectively, which were less than other reports. Besides, the amount of the contrast ratio (the di?erence between the margin values for logics 1 and 0) for the proposed structure was calculated by about 82%. The correct switching operation, compactness, and ultra-fast response, as well as the high contrast ratio, make the presented switch for optical integrated circuits.
关键词： optical switch,photonic crystal,graphene,photonic band gap,kerr e?ect
更新于2025-09-12 10:27:22
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p-type Cu3BiS3 thin films for solar cell absorber layer via one stage thermal evaporation
摘要： Ternary copper sulphides, especially copper-bismuth-sulphide (Cu-Bi-S), are alternative solar absorber materials due to their earth-abundant and non-toxic constituent elements, compared to the conventional copper indium gallium sulphide and cadmium telluride films. In this study, Cu-Bi-S thin films were deposited onto soda lime glass substrates using a one stage co-evaporation process from Cu2S and Bi2S3 sources, with the deposition temperatures varied from room temperature to 400°C. X-ray diffraction analysis confirmed that Cu3BiS3 was the dominant phase in the Cu-rich films, and the crystalline quality of the films was significantly improved with increasing the deposition temperature. An optical bandgap of 1.4 eV was achieved for the film deposited at 400°C, which demonstrated a Hall mobility of 3.95 cm2/V-s and a carrier concentration of 7.48 × 1016 cm-3. Cu3BiS3 films deposited at 375 and 400°C were implemented into superstrate solar cell structures (glass/ITO/n-CdS/p-Cu3BiS3/Al).
关键词： p-Cu3BiS3,optical band gap,thermal co-evaporation,thin film solar cell,absorber layer
更新于2025-09-12 10:27:22
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Studies on the developing of Nano-Structured Cu2S film for photovoltaic application
摘要： Current efforts have been given to develop new photovoltaic materials to improve the efficiency with reducing cost. The factors that have been taken into account in developing new photovoltaic materials include: a suitable energy band gap, the possibility of depositing the material using low cost deposition methods, abundance of the elements and low environmental costs with respect to the synthesis of the elements, production, operation and disposal of modules. It’s been a long time that continuous efforts has been given to find out the most appropriate material to be employed as absorber material for solar cell and some advanced material has been proposed too as potential solar cell material. Here in our present study we have taken Cu2-xS as a suitable p-type absorber layer material but the formation of stable Cu2-xS film was being difficult task. Different researchers proposed different methods among them we have found the elemental stacked layer deposition method is one of the promising technique. But this technique requires further optimization on thickness and layer no’s to get the best result with required stoichiometry. With this context we have tried to optimize the thickness and layer no’s for developing multilayer Cu2-xS thin film on the glass substrate by physical vapour deposition technique. The results obtained in this method shows that the optimum numbers of layer is 10 ensures formation of crystalline Cu2S structure with optical band gap is around 1.65 eV to 1.85 eV by different characterization technique like XRD, EDX, SEM, Spectrophotometry and PL. The I-V characteristic of Schotkey junction using silver and bulk resistance (ρb) with the sample shows semiconductor behaviour of the same. To the best of our knowledge this is the first time such type of nano-structured Cu2S film fabrication is reported.
关键词： Cu2S,Elemental stacked layer,Absorber layer,Optimization,Physical vapour deposition,Band gap
更新于2025-09-12 10:27:22
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Alloyed Ag2SexS1-x quantum dots with red to NIR shift: the band gap tuning with dopant content for energy harvesting applications
摘要： Alloyed quantum dots have pulled in a large consideration because of their fascination from visible to near infrared regime. In this work, quantum dots of alloyed Ag2SexS1-x (x = 0, 0.4, 0.6, 1.0) system are synthesized by making use of a simple intermediate temperature method. The structure and morphology of Ag2SexS1-x quantum dots are examined through X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and Raman spectroscopy. The X-ray diffraction data indicates monoclinic and orthorhombic structure of Ag2SexS1-x quantum dots. The size and composition controlled optical bandgap of Ag2SexS1-x quantum dots is meticulously looked into by Ultraviolet-Visible-Near Infrared absorption spectroscopy. The size of alloyed Ag2SexS1-x quantum dots varies from 3.5 nm to 4.8 nm. The bandgap of Ag2SexS1-x quantum dots has varied from 1.35 eV to 0.88 eV as calculated by Tauc plot. The observed values of bandgap indicate quantum confinement in two regimes-weak and strong confinement regimes. The results show that quantum confinement depends on both the size and composition of Ag2SexS1-x quantum dots. The alloying of Se to Ag2S has been confirmed using the Raman spectroscopy. These alloyed quantum dots might be reasonable for catching solar energy particularly from visible to NIR regime.
关键词： Alloyed Quantum Dots,Solar Energy,Quantum Confinement,Optical Band Gap
更新于2025-09-12 10:27:22