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oe1(光电查) - 科学论文

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出版时间
  • 2019
研究主题
  • solar cell
  • thin film
  • sputtering
  • Tungsten di sulfide (WS2)
应用领域
  • Optoelectronic Information Materials and Devices
机构单位
  • Universiti Kebangsaan Malaysia
  • German Malaysian Institute
  • Universiti Tenaga Nasional
143 条数据
?? 中文（中国） ▾

  • Tetragonal tungsten bronze phase thin films in the Ka??Naa??Nba??O system: Pulsed laser deposition, structural and dielectric characterizations

    摘要： Pulsed laser deposition parameters have been determined to synthesize pure Tetragonal Tungsten Bronze (TTB) phase thin films in the (K,Na)-Nb-O system (KNN). In relation to the high volatility of alkaline elements, it was found that the target composition and the target-substrate distance are of first importance. The TTB phase was identified by X-ray and electron diffraction and the surface microstructure consisting mainly of nanorods supports the formation of hallmark of the TTB phase. Poly-oriented nanorods have been obtained on both C-plane sapphire and (111)Pt/TiO2/SiO2/(001)Si substrates whereas horizontal nanorods oriented along the (hk0) planes have been grown on (100) and (110) SrTiO3. All the nanorods are parallel together when grown on (110) SrTiO3 and they present two in-plane orientations rotated of 90° from each other on (100) SrTiO3. Dielectric characteristics (dielectric permittivity e r, and loss tangent tand ) have been measured at low (1 kHz - 1 MHz) and high (1 GHz - 40 GHz) frequencies, on films deposited on Pt coated silicon and sapphire, respectively. A value of e r = 200 at 1 kHz with tand = 0.015 were measured in a parallel plate capacitor configuration, whereas e r = 130 and tand = 0.20 at 10 GHz were retrieved from transmission lines printed on the KNN TTB thin film grown on C-plane sapphire. Raman investigations of the TTB films were performed in the temperature range 77 - 873 K, confirming the TTB phase formation and the absence of structural transition. Piezoelectric Force Microscopy measurements evidenced a piezoelectric signal although no switching could be performed. However the dielectric measurements, complicated by high leakage currents when a DC voltage was applied, did not evidence any proof of ferroelectricity for the undoped KNN TTB films whereas results reported on other niobates (A,A')0.6Nb10O30 (with A: K, Na and A': Sr, Ba, Ca) have shown Curie temperatures, lying between 156°C and 560°C, separating the paraelectric phase (space group: P4/mbm N°127) and the ferroelectric one (space group: P4bm N°100).

    关键词： Tetragonal Tungsten Bronze,Nanorods,Dielectric characterizations,K-Na-Nb-O system,Pulsed laser deposition

    更新于2025-09-23 15:19:57

  • Tungsten-Doped Zinc Oxide and Indiuma??Zinc Oxide Films as High-Performance Electron-Transport Layers in Na??Ia??P Perovskite Solar Cells

    摘要： Perovskite solar cells (PSCs) have attracted tremendous research attention due to their potential as a next-generation photovoltaic cell. Transition metal oxides in N–I–P structures have been widely used as electron-transporting materials but the need for a high-temperature sintering step is incompatible with flexible substrate materials and perovskite materials which cannot withstand elevated temperatures. In this work, novel metal oxides prepared by sputtering deposition were investigated as electron-transport layers in planar PSCs with the N–I–P structure. The incorporation of tungsten in the oxide layer led to a power conversion efficiency (PCE) increase from 8.23% to 16.05% due to the enhanced electron transfer and reduced back-recombination. Scanning electron microscope (SEM) images reveal that relatively large grain sizes in the perovskite phase with small grain boundaries were formed when the perovskite was deposited on tungsten-doped films. This study demonstrates that novel metal oxides can be used as in perovskite devices as electron transfer layers to improve the efficiency.

    关键词： transparent metal oxide,zinc–oxynitride,perovskite solar cell,tungsten-doped InZnO

    更新于2025-09-23 15:19:57

  • Nonvolatile Programmable WSe <sub/>2</sub> Photodetector

    摘要： Optoelectronic devices with nonvolatile memory are an important component in a wide variety of applications ranging from optoelectronic random-access-memories, with the advantage of using optical stimuli as an added parameter, to complex artificial neuromorphic networks that pretend to mimic the working schemes of the human brain. In the past few years, 2D materials have been proposed as attractive candidates to build such optoelectronic devices with memory due to their excellent optoelectronic properties and high sensitivity to external electric fields. Here, a WSe2 monolayer p–n junction working as a nonvolatile programmable photodetector is reported, that, enabled by a split-gate configuration with embedded charge-trapping layers, is capable of retaining custom responsivity values over time, prior configuration by the user. Once configured, this photodetector can operate without external applied bias voltage as a self-driven photodetector, as well as without external back-gate voltage thanks to the charge stored in the floating gates. Furthermore, the device shows a remarkable performance, with open-circuit voltage around 1 V at approximately 270 W m?2 white light, fill factor higher than 30%, and fast response times. This programmable photodetector sets a new concept as a building block in more complex image-sensing systems.

    关键词： programmable photodetector,tungsten-diselenide,2D materials,photodetectors,floating gates,nonvolatile memories

    更新于2025-09-23 15:19:57

  • Selective Laser Melting and Remelting of Pure Tungsten

    摘要： The processing of pure tungsten encounters a substantial challenge due to its high melting point and intrinsic brittleness. Selective laser melting (SLM) technique is gaining popularity and offers an excellent processing approach for refractory metals. Herein, dense pure tungsten specimens are produced by optimizing SLM processing parameters. The mechanical property of the SLM-produced tungsten with an ultimate compressive strength of about 1200 MPa, which is obviously superior to that reported in other literature, is achieved. The increased laser energy input is instrumental in raising density and surface roughness of tungsten specimens. Interestingly, additional remelting of processed layers during SLM improves the surface quality and the microstructure and achieves the highest relative density (98.4% (cid:1) 0.5%). After laser remelting, the surface roughness is reduced by 28% and a large number of ?ne grains are obtained. The ?ow of ?uids caused by remelting plays a decisive role in the formation of ?ne grains and the defect level. Therefore, these ?ndings offer a new insight into SLM of pure tungsten.

    关键词： microstructure,tungsten,selective laser melting,mechanical properties,laser remelting

    更新于2025-09-23 15:19:57

  • Ultrathin Plasmonic Tungsten Oxide Quantum Wells with Controllable Free Carrier Densities

    摘要： We report the colloidal synthesis of ~3 tungsten-oxygen (W-O) layer thick (~1 nm), two-dimensional (2D) WO3-x nanoplatelets (NPLs) (x ~ 0.55 — 1.03), which display tunable near-infrared localized surface plasmon resonances (LSPR) spectra and high free electron density (Ne) that arises predominantly from their large shape factor. Importantly, the W to O composition ratios inferred from their LSPR measurements show much higher percentage of oxygen vacancies than those determined by X-ray diffraction analysis, suggesting that the aspect ratio of ultrathin WO3-x NPLs is the key to producing an unprecedentedly large Ne, although synthesis temperature is also an independent factor. We find that NPL formation is kinetically controlled, whereas thermodynamic parameter manipulation leads to Ne as high as 4.13 X 1022 cm-3, which is close to that of plasmonic noble metals, and thus our oxide-based nanostructures can be considered as quasi-metallic. The unique structural properties of 2D nanomaterials along with the high Ne of WO3-x NPLs provide an attractive alternative to plasmonic noble metal nanostructures for energy conversions.

    关键词： Ultrathin Plasmonic Tungsten Oxide,Quantum Wells,Colloidal Synthesis,Localized Surface Plasmon Resonances,Free Carrier Densities

    更新于2025-09-23 15:19:57

  • Metal-Reduced WO3a??x Electrodes with Tunable Plasmonic Resonance for Enhanced Photoelectrochemical Water Splitting

    摘要： Photoelectrochemical (PEC) water splitting is one of the most promising green technologies for producing renewable clean hydrogen energy. Developing plasmonic semiconductors with tunable plasmonic resonance to visible light has drawn increasing attention in view of utilizing abundant low-energy photons for solar-to-chemical conversion. Herein, we demonstrate for the first time that the WO3 electrode can be partly reduced by various metal foils in acid solution, showing strong localized surface plasmon resonance (LSPR) in the visible-to-near-infrared (Vis–NIR) region. The LSPR can be precisely tuned by using metal foils with different standard electrode potentials for different reaction times, and the LSPR peak position strongly depends on the concentration of W5+ in the WO3?x electrodes. A photocurrent density of 0.79 mA·cm?2 at 1.23 VRHE, which is twice that of pristine one, is obtained over an optimally reduced WO3?x electrode. The enhanced PEC water splitting performance is ascribed to the increased light absorption, conductivity and charge carrier concentration.

    关键词： photoelectrochemical water splitting,semiconductor,plasmonic resonance,metal foil,tungsten oxide

    更新于2025-09-23 15:19:57

  • Triplea??wavelength Qa??switched ytterbiuma??doped fiber laser based on tungsten oxide as saturable absorber

    摘要： In this article, a multiwavelength Q-switched ytterbium-doped fiber laser using tungsten oxide nanoparticles (WO3 NPs) as a saturable absorber (SA) is reported for the first time. The SA was prepared by depositing micron-sized layers of WO3 NPs suspension onto the surface of the fiber tip via direct deposition process. After embedding the SA into an ytterbium-doped fiber laser cavity, self-starting Q-switched performance was realized at a bleaching threshold of 179 mW having a minimum pulse width of 2.92 μs and maximum pulse energy of 9.26 nJ with variable repetition rates from 14.8 to 71.3 kHz. By boosting the pump power and proper adjustment of the polarization controller, steady dual- and triple-wavelength operations were obtained at pump powers of 210 and 275 mW, respectively. The obtained results confirm the practical use of WO3 as an effective nonlinear modulator for multiwavelength and pulsed fiber lasers near 1 μm wavelength band.

    关键词： multiwavelength,passive saturable absorber,YDFL,Q-switching,tungsten oxide nanoparticles

    更新于2025-09-23 15:19:57

  • Numerical simulation for optimization of an ultra-thin n-type WS2/p-type c-Si heterojunction solar cells

    摘要： Recently, ultra-thin tungsten disul?de (WS2) has become one of the hot spots in the research of solar cell materials due to its excellent optical and electrical properties. In this study, we use AFORS-HET software version 2.5 at air mass 1.5 to simulate the structure of n-type WS2/p-type c-Si heterojunction solar cells. Our goal is to ?nd an appropriate way to improve the performance of n-type WS2/p-type c-Si heterojunction solar cells by simulation. Through optimizing the parameters of both WS2 layer and Si layer, we obtain a maximum photovoltaic conversion e?ciency of 20.57%. Subsequently, we investigate the in?uence of the ITO work function and the interface states on the performance of n-type WS2/p-type c-Si heterojunction solar cells. It’s found that through selecting the suitable ITO work function and decreasing the interface defect density, solar cell’s performance can be further improved. Our result indicates that ultra-thin WS2 is a promising photovoltaic material for the application in solar cells.

    关键词： Work function,Heterojunction solar cells,Numerical simulation,Tungsten disul?de,Interface states

    更新于2025-09-23 15:19:57

  • Preparation, microstructure, and microhardness of selective laser-melted Wa??3Ta sample

    摘要： Tungsten (W) alloy is of difficulty in processing for conventional way because of its high melting point. Here, W alloy sample with the addition of 3 wt% Ta was prepared by selective laser melting. The influence of volumetric energy density (VED) on the surface morphology and the relative density was discussed, and microstructure, phase composition, and microhardness were investigated. The results show that a smooth surface and high relative density (95.79%) can be obtained under optimal VED. The W–Ta substitutional solid solution formed because of the replacement of Ta atom. There are strip and block fine grains in the W–3Ta sample with no significant texture. In addition, subgrain structure with a size of around 1 lm formed inside the strip grain, owing to the large thermal gradient and extremely fast cooling rate. Finally, the W–3Ta alloy shows higher microhardness than that obtained by traditional methods.

    关键词： tungsten alloy,volumetric energy density,microstructure,microhardness,selective laser melting

    更新于2025-09-23 15:19:57

  • Highly efficient bio-based porous carbon hybridized with tungsten carbide as counter electrode for dye-sensitized solar cell

    摘要： Bio-based porous carbon (CMA and CTA) are successfully prepared from waste carton via microwave-assisted activation (MA) and two-step chemical activation (TA) methods, respectively. The as-prepared CTA sample exhibits higher specific surface area (824.16 m2 g?1) and larger total pore volume (0.71 cm3 g?1), as compared with those of the CMA sample (655.36 m2 g?1 and 0.62 cm3 g?1, correspondingly). The higher specific surface area could provide more catalytic sites; thus, the dye-sensitized solar cell (DSSC) assembled with a CTA counter electrode (CE) deliver a power conversion efficiency (PCE) of 6.76%, surpass the CMA-based DSSC (6.19%). Further, tungsten carbide (WC) are introduced into CTA and CMA to form hybrid catalysts (WC/CTA and WC/CMA, respectively) in order to improve their catalytic activities. Benefitting from the synergistic effect of bio-based porous carbon and WC, the DSSCs with WC/CTA and WC/CMA CEs exhibit superior PCE values of 7.32% and 6.85%, respectively, close to Pt (7.51%). This work provides an effective strategy for synthesizing low-cost and high-performance hybrid catalysts from bio-based carbon to achieve resource utilization of biomass waste in new energy fields.

    关键词： Electrocatalyst,Counter electrode,Bio-based carbon,Tungsten carbide,Dye-sensitized solar cell

    更新于2025-09-23 15:19:57