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Sol-gel processed vanadium oxide as efficient hole injection layer in visible and ultraviolet organic light-emitting diodes
摘要： Low-cost, high-throughput and scalable production currently boosts organic electronic device towards solution processing. Sol-gel processed aqueous vanadium oxide (h-VOx) is facilely synthesized and proven to be efficient hole injection layer (HIL) in visible and ultraviolet organic light-emitting diodes (OLEDs). Atomic force microscopy and X-ray/ultraviolet photoelectron spectroscopy measurements indicate that h-VOx behaves superior film morphology and exceptional electronic properties such as oxygen vacancy dominated non-stoichiometry and appropriate surface work function. With tris(8-hydroxy-quinolinato)aluminium as emitter, the visible OLED gives maximum luminous and power efficiencies of 6.3 cd/A and 3.2 lm/W, respectively, which are slightly superior to the counterpart with vacuum thermally-evaporated VOx (5.6 cd/A and 2.7 lm/W). With 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter, the ultraviolet OLED produces attractive short-wavelength emission of 379 nm with full width at half maximum of 40 nm and improved durability. The maximum radiance and external quantum efficiency reach 15.3 mW/cm2 and 2.92%, respectively, which are considerably enhanced in comparison with the corresponding reference (11.9 mW/cm2 and 2.32%). Current versus voltage characteristics and impedance spectroscopy analysis elucidate that h-VOx exhibits robust hole injection and accordingly high-performance OLEDs. Our results pave an alternative way for advancing organic electronic devices and VOx applications with solution process.
关键词： Organic light-emitting diode,Hole injection,Solution process,Vanadium oxide,Sol-gel method
更新于2025-11-20 15:33:11
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A microfluidic all-vanadium photoelectrochemical cell with the N-doped TiO2 photoanode for enhancing the solar energy storage
摘要： In this work, the nitrogen-doped TiO2 photocatalyst is synthesized and applied in a microfluidic all-vanadium photoelectrochemical cell for enhancing the solar energy storage. The use of the nitrogen-doped TiO2 photoanode and the minimization design can ensure the visible-light response, increased specific surface area, vigorous pore structure and enhanced photon and mass transport as well as more uniform light distribution. Various characterizations are performed to evaluate the developed photocatalyst and microfluidic all-vanadium photoelectrochemical cell. The results confirm that the developed nitrogen-doped TiO2 photoanode can provide both the extended absorption spectrum and the small anatase crystal size as well as the obviously enlarged specific surface area with plentiful pore structure. Because of these merits, the microfluidic all-vanadium photoelectrochemical cell with the nitrogen-doped TiO2 photoanode yield the average photocurrent density of 0.103 mA/cm2 during the long-term operation, which is much higher than those with the un-doped TiO2 photoanode (0.086 mA/cm2) and commercial P25 TiO2 photoanode (0.073 mA/cm2), presenting 19.8% and 41% improvements, respectively. The results demonstrate not only the promotion of the vanadium reversible redox pairs conversion but also the inherently excellent stability by the nitrogen-doped TiO2 photoanode.
关键词： Photoanode,N-doped TiO2 photocatalyst,Conversion rate,Microfluidic all-vanadium photoelectrochemical cell,Solar energy storage
更新于2025-11-14 17:03:37
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Epitaxial Liftoff of Wafer‐Scale VO <sub/>2</sub> Nanomembranes for Flexible, Ultrasensitive Tactile Sensors
摘要： Highly sensitive tactile sensors with long-term stability and low power consumption are one of the key components for flexible electronics. Here, for the first time, the fabrication of VO2 nanomembrane tactile sensors by epitaxial liftoff from ZnO sacrificial layer is reported. The wafer-scale nanomembranes inherit the structural and electrical properties of the as-grown films, and the wet transfer generates negligible influence on the quality of VO2. Most importantly, giant electrical responses to external strains are found due to the release of substrate clamping, and a high gauge factor up to ≈1100 is derived. Furthermore, the electrical properties show no deterioration after repeatedly bending the nanomembranes for 10 000 times at a radius of 1 cm. The VO2 nanomembrane sensors are utilized to monitor the radial artery pulse, and totally reproducible waveforms with ultrahigh sensitivity to the tactile stimuli are observed. Moreover, the power dissipation of the VO2 tactile sensors can be lowered down to the picowatt level, allowing for the future construction of self-powered sensing systems together with nanogenerators. This study provides a substantial step toward large-scale preparation of oxide nanomembranes and therefore paves a promising way for flexible oxide electronics.
关键词： flexible electronics,piezoresistivity,vanadium dioxide,tactile sensors,epitaxial liftoff
更新于2025-11-14 17:03:37
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E‐Waste Based V <sub/>2</sub> O <sub/>5</sub> /RGO/Pt Nanocomposite for Photocatalytic Degradation of Oxytetracycline
摘要： The increasing prevalence of antibiotics in the environment has promoted the development of antibiotic resistant microorganisms, and novel approaches are needed to effectively remove antibiotics from water and mitigate this worldwide problem. A reduced graphene oxide-V2O5 (RGOV) nanocomposite was synthesized and used for photocatalytic degradation of the antibiotic oxytetracycline (OTC) in aqueous solution. The Sol–Gel method was employed for V2O5 synthesis from e-waste-based vanadium nitrate, and a one pot solvothermal method was used to synthesize RGOV. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM) with energy dispersive analysis of X-rays (EDAX) confirmed V-O-C bonds on the surface of the RGOV nanocomposites. A decrease in the band gap of V2O5 from 2.21 to 2.13 eV was supported by diffuse reflectance ultraviolet–visible spectrophotometry. OTC adsorption onto the nanocomposite increased with an increase in RGO concentration and saturated at 17% for RGOV with 30% graphene oxide. The composite degraded 90% of the OTC present in aqueous solution (50 mg/L). Platinum (1%) doping further increased OTC degradation by the nanocomposite to 98.7%. Optimum conditions for maximum OTC degradation are (1) an initial OTC concentration of 50 mg/L, (2) a RGOV nanocomposite dose of 0.5 g/L, and (3) a 40 min incubation time. Our results support the potential use of RGOV nanocomposite for OTC photodegradation.
关键词： vanadium pentoxide,photocatalytic degradation,nanocomposite,E-waste,RGO,oxytetracycline
更新于2025-09-23 15:23:52
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Numerical investigation of energy performance and cost analysis of Moroccan’s building smart walls integrating vanadium dioxide
摘要： Thermochromic materials such as vanadium dioxide (VO2) have the capability to regulate their infrared reflectivity depending on ambient temperature. Such smart materials are attractive for applications like smart windows and smart roofs. In this paper, we investigate numerically the impact of tungsten (W) doped VO2 application as a smart outdoor wall layer on the building energy consumption in the Mediterranean climate. Temperature distributions through wall configurations with and without W doped VO2 were calculated using finite differences method implemented in Matlab environment. Calculations take into consideration dynamic variations of W doped VO2 absorptivity depending on outdoor temperature variations. Decrement factor, time lag, transmission and peak loads of cooling and heating were calculated. Results have shown that the indoor surface temperature is attenuated during summer by 2–3 °C depending on orientation. Cooling energy saving due to the use of W doped VO2 in summer is around 70% monthly which is equivalent to save $21.6/month of electricity invoiced amount. During winter, W doped VO2 maintains the same value of absorptivity as the uninsulated wall. Thus, results show small differences for indoor surface temperature and heating energy consumption. The application of W doped VO2 in intelligent thermal wall insulation offers a real-time dynamic variation of building’s envelope solar absorptivity and makes smart walls concept more feasible.
关键词： Energy efficiency,Smart wall,Radiative thermal rectification,Thermochromic,Real-time dynamic absorptivity,Vanadium dioxide
更新于2025-09-23 15:23:52
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Oxidation/reduction control of the VO2 nanoparticle in the nano-confined space of the hollow silica nanoparticle
摘要： Vanadium dioxide (VO2) exhibits a good thermochromic property which can be used in a smart window. To improve its poor visible transparency, immobilization of the VO2 nanoparticles on the silica shell of hollow nanoparticles was proposed. In addition to improving the particle dispersibility of the VO2 and to reducing stress from repeated phase transitions of the VO2 between monoclinic and tetragonal, the hollow interior can reduce any undesirable oxidation of the VO2 to V3O7, V2O5, etc., along with the thermal decomposition behavior of organic compounds around the vanadium atom. The hollow silica nanoparticles with micropores (less than 2 nm) were prepared by a previously-reported template method. Through the pores, the vanadium precursor with a chelate ligand solution penetrates into the hollow interior. The vanadium intermediate formed by adding water was then captured by the silica shell. During the crystallization process under a nitrogen atmosphere, 10-30 nm of VO2 particles were immobilized on the silica shell with a high dispersibility by optimization of the vanadium precursor concentration, and ratios of vanadium/water and vanadium/hollow silica nanoparticles. The VO2/hollow silica nanoparticles in water exhibited a higher visible transparency than that of the commercial VO2. In addition, their thermochromic property in the infrared region was close to that of the commercial one.
关键词： Thermochromic,Hollow silica nanoparticle,Vanadium dioxide,Micropore
更新于2025-09-23 15:23:52
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Thickness-modulated thermochromism of vanadium dioxide thin films grown by magnetron sputtering
摘要： Vanadium dioxide (VO2) films were prepared on soda-lime glass by direct current magnetron sputtering at 320 °C. Effects of film thickness on the microstructure, surface morphology and thermochromic performance of VO2 films were investigated. X-ray diffraction showed that the deposited films have strong preferred orientation of VO2 (011) lattice when the film thickness higher than 102 nm. The calculated grain sizes of VO2 films increased from 16.05 nm to 34.56 nm continuously with the increasing of film thickness. UV/VIS/NIR spectrophotometer showed that the visible transmittance deceased while the infrared transmittance switching efficiency increased as the film thickness increased from 79 nm to 264 nm. Additionally, the optical band gaps of VO2 films were in a range of 1.15 eV–1.40 eV, and the thicker film exhibited the smaller value. Moreover, the results of measured temperature-dependent electrical resistivity of these VO2 films showed that the phase-transition temperature is in a range of 53–60 °C, which is much lower than that of single-crystal VO2 (68 °C). With the film thickness increasing, the metal–semiconductor phase transition becomes more obvious. Overall, films with thickness in the range of 80–100 nm showed comparatively relatively balanced combination of visible transmittance and solar switching efficiency.
关键词： Thermochromic performance,Film thickness,Vanadium dioxide,Magnetron sputtering
更新于2025-09-23 15:23:52
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Growth of vanadium dioxide nanostructures on graphene nanosheets
摘要： The metal oxide/graphene hybrid nanomaterials have been known as promising functional materials for advanced applications such as high capacitive electrode material of secondary batteries, and high sensitive material of high performance gas sensors. Here, morphology controlled vanadium dioxide (VO2) nanostructures were grown on Si wafer and exfoliated graphene by the vapor transport method using a horizontal furnace system. One-dimensional VO2 nanowires were grown on SiO2(300 nm)/Si substrate under 0.4 kPa condition. On the other hand, thick polycrystalline of VO2 platelets were grown on exfoliated graphene nanosheets under 0.4 kPa condition. In addition, polycrystalline VO2 platelets were only grown on exfoliated graphene nanosheets under 101 kPa (atmospheric pressure) condition. The growth of polycrystalline VO2 platelets on graphene nanosheets in atmospheric pressure condition is attributed to preferential growth on functional group of graphene surface such as carbonyl. The functional group is served as nucleation site of VO2 nanostructures.
关键词： Nanostructures,Hybrid Nanomaterials,Vapor Transport Method,Graphene,Vanadium Dioxide
更新于2025-09-23 15:23:52
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Characteristics of Vanadium Oxide Thin Films Fabricated by Unbalanced Magnetron Sputtering for Smart Window Application
摘要： Vanadium oxide (VOx) thin films were deposited by an unbalanced magnetron (UBM) sputtering system with a vanadium metal target and O2 reaction gas, and thermally treated at various annealing temperatures. In this work, the structural, electrical, and optical properties of the fabricated VOx films with various annealing temperatures were experimentally investigated. The UBM sputter grown VOx thin films exhibited amorphous structure, and had a very weak peak of V2O5 (002) owing to very thin films. However, the crystallite size of VOx films increased with increasing annealing temperature. The surface roughness of VOx films and average transmittance decreased with increasing annealing temperature. The resistivity of VOx films also decreased with increasing annealing temperature, while the electrical properties of films improved.
关键词： Transmittance,Unbalanced Magnetron Sputtering,Vanadium Oxide,Surface Roughness,Resistivity
更新于2025-09-23 15:23:52
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Universal renormalization group flow toward perfect Fermi-surface nesting driven by enhanced electron-electron correlations in monolayer vanadium diselenide
摘要： Reducing the thickness of three-dimensional samples on appropriate substrates is a promising way to control electron-electron interactions, responsible for so called electronic reconstruction phenomena. Although the electronic reconstruction has been investigated both extensively and intensively in oxide heterostructure interfaces, this paradigm is not well established in the van der Waals heterointerface system. In the present study, we examine the nature of a charge ordering transition in monolayer vanadium diselenide (VSe2). This two-dimensional phase transition would be distinguished from that of VSe2 bulk samples, driven by more enhanced electron-electron correlations. We recall that VSe2 bulk samples show a charge-density-wave (CDW) transition around TCDW ～ 105 K. This bulk phase transition results from Fermi-surface nesting properties, where the low-temperature CDW state coexists with itinerant electrons of residual Fermi surfaces. Recently, angle-resolved photoemission spectroscopy measurements [Nano Lett. 18, 5432 (2018)] uncovered that the Fermi-surface nesting becomes perfect, where the dynamics of hot electrons is dispersionless along the orthogonal direction of the nesting wave vector. In addition, scanning tunneling microscopy measurements [Nano Lett. 18, 5432 (2018)] confirmed that the resulting CDW state shows essentially the same modulation pattern as the three-dimensional system of VSe2. Here, we perform the renormalization group analysis based on an effective-field theory in terms of critical CDW fluctuations and hot electrons of imperfect Fermi-surface nesting. As a result, we reveal that the imperfect nesting universally flows into perfect nesting in two dimensions, where the Fermi velocity along the orthogonal direction of the nesting vector vanishes generically. We argue that this electronic reconstruction is responsible for the observation [Nano Lett. 18, 5432 (2018).] that the CDW transition temperature is much more enhanced to be around TCDW ～ 350 K than that of the bulk sample.
关键词： vanadium diselenide,electron-electron correlations,renormalization group,Fermi-surface nesting,charge-density-wave transition
更新于2025-09-23 15:23:52