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Low-Temperature Laser Synthesis of Thin Electrochromic WO3 Films
摘要： Amorphous dielectric WO3 films with a surface roughness from 4 to 5 nm have been grown by room-temperature pulsed laser deposition on quartz and c-sapphire substrates using metallic targets. We have examined the effect of the nature of the substrates and the oxygen pressure during the growth process on the transmission spectrum of the WO3 films in the range from 400 to 2000 nm. The parameters of the films have been shown to depend on the oxygen pressure during the growth process. Raising the oxygen pressure from 20 to 60 mTorr during the film growth process increases the transmission of the WO3 films from 40 to 75% in the visible and UV spectral regions and from 10 to 70% in the IR. With increasing oxygen pressure during film growth, the band gap of the WO3 films increases from 3.01 to 3.34 eV in the case of sapphire substrates and from 2.95 to 3.42 eV in the case of quartz substrates, being only slightly dependent on the nature of the substrate. Using a WO3 film grown at room temperature, we have fabricated the first thin-film liquid-electrolyte electrochromic cell. Its transmission in the spectral range from 300 to 900 nm drops by 30% at an applied voltage of 2.5 V, with a coloration time on the order of 2 min.
关键词： electrochromic cell,room-temperature pulsed laser deposition,thin WO3 films
更新于2025-09-23 15:21:01
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Portable Instrument for Monitoring Environmental Toxins Using Immobilized Quantum Dots as the Sensing Material
摘要： A portable instrumental system was designed for the routine environmental monitoring of toxic volatile organic compounds (VOCs) in atmospheric conditions based on changes in the photoluminescence emission of semiconductor nanoparticles (quantum dots) entrapped in a sol-gel matrix as the solid sensing material. The sol-gel sensing material displayed a long-lived phosphorescent emission, which is quenched in the presence of trace levels of a volatile organic compound (acetone) in gaseous atmospheres. The developed instrument could measure and process the changes in the photoluminescence of the sensing material after exposure to gaseous acetone. The developed prototype device consists of a deep-ultraviolet light-emitting diode (UV LED), which excites the chemical sensing material; an optical filter to remove scattered light and other non-desirable wavelengths; a photomultiplier tube (PMT) to convert the phosphorescence emission of the sensor phase to an electrical signal; and a microcontroller to correlate the signal with the analyte concentration. The developed prototype was evaluated for its ability to measure low levels of gaseous acetone in contaminated atmospheres with high sensitivity (detection limit: 9 ppm). The obtained results show the feasibility of this type of instrument for environmental analytical control purposes.
关键词： quantum dots (QDs),photomultiplier,UV LED,instrumentation,nanoparticles,room temperature phosphorescence (RTP)
更新于2025-09-23 15:21:01
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Resistive switching and electric field control of ferromagnetism in SnO2 films deposited at room temperature
摘要： The SnO2 film deposited at room temperature (RT) on the substrate of Pt/Ti/SiO2/Si is nano-crystallized, which exhibits room temperature ferromagnetism (FM) due to the oxygen vacancies of SnO2 film. The bipolar and multilevel resistive switching (RS) can be observed in the Ta/SnO2/Pt devices, where SnO2 film was deposited at RT. The Ta/SnO2/Pt device has a large ON/OFF ratio (27000) and multilevel RS, which is of great significance for high-density data storage applications. The saturation magnetization of Ta/SnO2/Pt/Ti/SiO2/Si (Ta/SnO2/Pt device) is almost the same as SnO2/Pt/Ti/SiO2/Si, which implies that the influence of Ta top electrodes on the saturation magnetization of Ta/SnO2/Pt/Ti/SiO2/Si is much less. The Ta/SnO2/Pt device shows the non-volatile and reversible saturation magnetization modulation between low resistance state (LRS) and high resistance state (HRS), which results from the formation/rupture of oxygen vacancy filaments. The saturation magnetization at LRS is higher than that at HRS. In addition, the saturation magnetization also enhances with an increase the magnitude of positive DC sweeping voltage. Without DC loop current, the saturation magnetization of Ta/SnO2/Pt increases with an application of positive electric field and drops again with an application of certain negative electric field. The saturation magnetization of Ta/SnO2/Pt can be reversibly modulated in non-volatile by only electric voltage without DC loop current. Such modulation of Ms by only electric voltage without loop DC current is connected with the change in Vo+ density in a certain range of SnO2 films.
关键词： oxygen vacancies,electric field control,room temperature ferromagnetism,resistive switching,SnO2 film
更新于2025-09-23 15:21:01
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Reduced graphene oxide hybridized with WS2 nanoflakes based heterojunctions for selective ammonia sensors at room temperature
摘要： Hybrid of the two dimensional nanostructured reduced graphene oxide (rGO) and WS2 has been investigated for a room temperature ammonia sensor. The formed rGO/WS2 heterojunctions prepared by one-step hydrothermal synthesis indicated a good sensitivity to different concentrations of ammonia from 10 ppm to 50 ppm at room temperature. The WS2 nanoflakes doped in the heterojunction plays significant role in the enhanced response through the introduction of more hydroxyls in rGO and the extra Lewis acid active centers. The sensor also shows an excellent selectivity to NO2, alcohols, formaldehyde，acetone and benzene and a good long term stability indicating a potential to be employed as a room temperature NH3 sensor.
关键词： rGO/WS2 heterojunctions,Room Temperature,Ammonia Sensors
更新于2025-09-23 15:21:01
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Annealing of Gadolinium-Doped Ceria (GDC) Films Produced by the Aerosol Deposition Method
摘要： Solid oxide fuel cells need a diffusion barrier layer to protect the zirconia-based electrolyte if a cobalt-containing cathode material like lanthanum strontium cobalt ferrite (LSCF) is used. This protective layer must prevent the direct contact and interdiffusion of both components while still retaining the oxygen ion transport. Gadolinium-doped ceria (GDC) meets these requirements. However, for a favorable cell performance, oxide ion conducting films that are thin yet dense are required. Films with a thickness in the sub-micrometer to micrometer range were produced by the dry room temperature spray-coating technique, aerosol deposition. Since commercially available GDC powders are usually optimized for the sintering of screen printed films or pressed bulk samples, their particle morphology is nanocrystalline with a high surface area that is not suitable for aerosol deposition. Therefore, different thermal and mechanical powder pretreatment procedures were investigated and linked to the morphology and integrity of the sprayed films. Only if a suitable pretreatment was conducted, dense and well-adhering GDC films were deposited. Otherwise, low-strength films were formed. The ionic conductivity of the resulting dense films was characterized by impedance spectroscopy between 300 ?C and 1000 ?C upon heating and cooling. A mild annealing occurred up to 900 ?C during first heating that slightly increased the electric conductivity of GDC films formed by aerosol deposition.
关键词： room temperature impact consolidation (RTIC),crystallite size,dense films,thermal powder treatment,electrical conductivity
更新于2025-09-23 15:21:01
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Ethanol–water-assisted room temperature synthesis of CsPbBr3/SiO2 nanocomposites with high stability in ethanol
摘要： All-inorganic halide perovskites have attracted great attention by virtue of the merits of bright emission, tunable wavelength and narrow-band emission. Despite the excellent optical features, all-inorganic halide perovskite materials have suffered from intrinsic instability, which has limited their applications in various optoelectronic devices. To mitigate the intractable issue, we demonstrated the CsPbBr3 nanoparticles decorated with smaller SiO2 nanocrystals to passivate the surface defects; SiO2 nanoparticles were applied as a barrier layer to maintain the optical property and enhance environmental stability. A facile in situ method was proposed to prepare CsPbBr3/SiO2 nanocomposites, in which an environmental ethanol/water solvent system was needed with the addition of tetraethyl orthosilicate (TEOS) as a silicon precursor. The obtained CsPbBr3/SiO2 nanocomposites have better optical characteristic and stability than bare CsPbBr3 nanoparticles. Even 70% photoluminescence intensity of as-prepared CsPbBr3/SiO2 nanocomposites can be maintained after 168 h storage in ethanol. This newly developed synthesis will open up a new route for the fabrication of optoelectronic devices in an environmentally friendly way, and the as-obtained perovskite materials with improved stability will make them great potential for multifunctional optoelectronic devices.
关键词： Ethanol–water-assisted room temperature synthesis,All-inorganic halide perovskites,High stability,CsPbBr3/SiO2 nanocomposites,Optoelectronic devices
更新于2025-09-23 15:21:01
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Room-temperature Sputtered NiOx for hysteresis-free and stable inverted Cs-FA mixed-cation perovskite solar cells
摘要： In this research, a room-temperature sputtering technology for fabricating high performance NiOx film was developed, which was applicable for inverted cesium (Cs)-formamidinium (FA) mixed-cation perovskite solar cells (PSCs). The Ni3t/Ni2t ratio in sputtered NiOx film was effectively adjusted by controlling Ar pressure while sputtering. NiOx films with appropriate Ni3t/Ni2t ratio exhibit uniform surface morphology, high transmittance, and better energy level match with the perovskite layer. By using this sputtered NiOx film as hole transporting layer, short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE) of a champion inverted PSC were 19.25 mA/cm2, 1.05 V, 0.80 and 16.23%, respectively. Also, these devices remained 90.6% of their initial PCE after light soaking at a surrounding temperature of 50°C for more than 600 h.
关键词： Stability,Room-temperature,Magnetron sputtering,Cs-FA mixed-cation perovskite,NiOx HTL
更新于2025-09-23 15:19:57
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Heavy Atom Effect of Selenium for Metal-Free Phosphorescent Light-Emitting Diodes
摘要： Room-temperature phosphorescence from metal-free purely organic molecules has recently gained much interest. We devised metal-free organic phosphors by incorporating selenium (Se) to promote spin?orbit coupling by its nonmetal heavy atom effect. The Se-based organic phosphors showed bright phosphorescent emission in organic light-emitting diodes (OLEDs) and photo-excited phosphorescence in an amorphous film state. Large orbital angular momentum change (ΔL) during the electron transition process and heavy atom effect of Se render a PL quantum yield of 0.33 ± 0.01 and a high external quantum efficiency (EQE) of 10.7 ± 0.14% in phosphorescent LEDs. This work demonstrates the rational molecular design of metal-free organic phosphorescent emitters with Se as an alternative novel class of materials to the conventional organometallic phosphors for OLEDs.
关键词： organic light-emitting diodes,spin?orbit coupling,selenium,metal-free organic phosphors,phosphorescent LEDs,room-temperature phosphorescence
更新于2025-09-23 15:19:57
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Controlled deposition of size-selected metal nanoclusters on prepatterned substrate
摘要： An endeavor of organizing Cu nano-particles of controlled size in ordered arrays at room temperature is reported. This involves the guided deposition of size-selected nanoparticles otherwise known as nanoclusters via periodic modulation of the substrate surface. Ultra-high vacuum compatible magnetron-based gas-aggregation type source combined with a quadrupole mass filter has been employed to produce the size-selected nanoclusters whereas the surface modulations (ripples) in the nanoscale are induced by low energy oblique angle ion beam irradiation. Morphological aspects of deposited nanoclusters and the substrates were characterized by high-resolution scanning electron microscopy (HRSEM) and atomic force microscopy (AFM). The chemical composition of the deposited nanoclusters was characterized by x-ray photoelectron spectroscopy. The alignment of size-selected metal nanoclusters along the substrate-patterns is observed. Depending upon deposition conditions quality of the organization varies. The optimum angle of deposition for the improved alignment depends on the pattern parameters of the substrate.
关键词： Ion sputtering,Room-temperature organization,Metal nanocluster,Patterned substrate,Supported clusters,Scanning Electron Microscopy
更新于2025-09-23 15:19:57
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All-Room-Temperature Processed 17.25%-Crystalline Silicon Solar Cell
摘要： In creating the next-generation of crystalline silicon (c-Si) solar cells, the goals are to improve energy conversion efficiency and reduce costs. Here, we demonstrate all-room-temperature-processed high-efficiency thin-film/c-Si heterojunction solar cells. Functional thin film multilayers of ITO/Ni/vanadium oxide (VOx) and barium oxide (BaOx)/Al are stacked on the front and rear sides, respectively. The comprehensive analysis revealed Ni and BaOx interlayers facilitated the selective collection of charge carriers. With the MgF2 antireflection layer, the efficiency of 17.25% was achieved, suggesting a strategy for the room-temperature fabrication of high-efficiency c-Si solar cells.
关键词： Si solar cells,Room-temperature,Vanadium oxide,Contact resistivity,Barium oxide
更新于2025-09-23 15:19:57