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oe1(光电查) - 科学论文

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出版时间
  • 2018
研究主题
  • thin-film transistors
  • N2O plasma treatment.
  • amorphous InGaZnO
  • gate-bias stress
  • stability
应用领域
  • Electronic Science and Technology
机构单位
  • Peking University
175 条数据
?? 中文（中国） ▾

  • aSi:H/i-aSi:H/p+aSiGe:H Graded Band Gap Single Junction Solar Cell

    摘要： In this paper, we present a single junction graded band gap thin film solar cell using heavily phosphorous doped amorphous silicon, intrinsic amorphous silicon and heavily boron doped amorphous silicon germanium. The first part of the work presents a rigorous analysis of J-V characteristics of recommended photovoltaic structure under short circuit (SC), open circuit (OC), dark and AM 1.5G illumination standard. Further, optimisation of thickness of active layers of the suggested n+aSi:H/i aSi:H/p+aSiGe:H solar cell structure is done using SCAPS1D solar simulator. The active layer thickness of the proposed solar cell is 430 nm only. Low active layer thickness and absence of multiple junctions reduces the material requirement, complexity and cost of the proposed solar cell. Furthermore, fabrication of individual layers and overall summary of their characterisation have been done. Finally, the proposed structure has been fabricated and validated its J-V characteristics. The fabricated solar cell has short circuit current density (Jsc) of 11.67 mA/cm2, open circuit voltage (Voc) of 1.18 V, fill factor (FF) of 0.857 and conversion efficiency (η) of 11.80 % which is on par with other announced single junction amorphous silicon solar cells. Here, we are reporting a single junction graded band gap solar cell using combination of aSi:H and aSiGe:H alloys with varying doping levels for the first time, which is better in conversion efficiency while compact and light.

    关键词： SCAPS1D,graded bandgap,amorphous silicon germanium,J-V characteristics,PECVD,Amorphous Silicon Alloys

    更新于2025-09-19 17:13:59

  • Relating fracture toughness to micro-pillar compression response for a laser powder bed additive manufactured bulk metallic glass

    摘要： A Zr-based bulk metallic glass produced using selective laser melting (SLM) was compared to the same alloy fabricated using traditional suction-casting. Analysis of the fracture toughness and mechanism through single edge notched beam bending experiments show a significantly reduced damage tolerance for the laser-processed material (KQ ~ 138.0 ± 13.1 → 28.7 ± 3.7 MPa √m), even though X-ray diffraction and microhardness responses were identical. Uncovered here using uniaxial quasistatic micro-pillar compression, as-cast samples more readily undergo shear transformations (evidenced through discrete load drops) below the nominal 0.2% yield stress, which can be connected to the higher macroscopic toughness. Differential scanning calorimetry demonstrated that the increased barrier to shear transformation for the SLM material could not be explained by the relative relaxation states. Rather, it is attributed to the greater dissolved oxygen concentration in the laser-processed material, which is postulated to decrease atomic mobility in the structure and thereby increase the activation energy required to initiate shear transformations.

    关键词： fracture toughness,metallic glass,amorphous materials,additive manufacturing,selective laser melting,micromechanics

    更新于2025-09-19 17:13:59

  • Visible-light-driven selective oxidation of methane to methanol on amorphous FeOOH coupled m-WO3

    摘要： Direct conversion of methane into value-added fuels or chemicals under ambient conditions remains a great challenge. Constructing solar-energy-driven catalytic systems is considered as a promising strategy, but the conversion e?ciency and products selectivity are still low, especially for producing alcohol derivatives. Herein, to promote the photocatalytic activity of methane partial oxidation to methanol, a series of FeOOH/m-WO3 consisting of ordered mesoporous WO3 (m-WO3) and highly dispersed amorphous FeOOH were synthesized by using KIT-6 silica as hard template. The prepared FeOOH/m-WO3 catalysts exhibit dramatically improved visible-light catalytic activities toward selective oxidation methane into methanol in the presence of H2O2. A methane conversion rate of 238.6 μmol·g?1·h?1 is achieved over the optimal 1.98% FeOOH/m-WO3, which is 3 times higher than that of pristine m-WO3 (79.2 μmol·g?1·h?1). Moreover, a methanol production rate of 211.2 μmol·g?1·h?1 with a selectivity of 91.0% is obtained on the optimum catalyst under 4 h visible-light irradiation. Signi?cantly, the greatly improved methane conversion and methanol production can be attributed to e?cient electron migration from the conduction band of m-WO3 to highly dispersed FeOOH, evidenced by in-situ XPS analysis, transient photocurrent response and photoluminescence spectra. Furthermore, based on radicals trapping experiments and electron spin resonance (ESR) results, methane is primarily activated by photoholes accumulated on the valence band of m-WO3 to generate methyl radicals (·CH3) and the produced hydroxyl radicals (·OH) via decomposing H2O2 by photoelectrons on FeOOH surface are predominant oxidant for methanol generation. Desired methanol is selectively produced via radicals reaction between ·CH3 and ·OH.

    关键词： WO3,Methane,Methanol,Visible-light-driven,Amorphous FeOOH

    更新于2025-09-19 17:13:59

  • Phase relation between supercooled liquid and amorphous silicon

    摘要： The phase relation between supercooled liquid silicon (l-Si) and amorphous silicon (a-Si) is discussed based on experimental results. Electrostatically levitated l-Si samples were supercooled down to low temperatures, 300 K below the melting temperature (Tcl: 1683 K), and solidified accompanied by the release of latent heat. It was found that solidified Si samples melted again at 1480 K caused by the latent heat. Also, it was found that the Si samples that rapidly quenched near the solidification temperature contained a large amount of a-Si with tetrahedral coordination. These two findings show that the supercooled l-Si samples solidified into a-Si and a-Si melted, confirming the idea of a first-order phase transition between two metastable phases proposed by Turnbull et al. [Metall. Mater. Trans. A 29, 1825 (1998)].

    关键词： supercooled liquid silicon,electrostatic levitation,amorphous silicon,latent heat,phase transition

    更新于2025-09-19 17:13:59

  • Theoretical investigation of broadband absorption enhancement in a-Si thin-film solar cell with nanoparticles

    摘要： Thin-film solar cells have attracted increasing attention due to its low material cost and large flexibility, but they also face the challenge of low solar absorption due to reduced active layer thickness. Through exciting surface plasmon resonance, plasmonic metal nanoparticles are usually placed on the cell front surface to enhance solar absorption. However, if eliminating the unuseful intrinsic absorption in nanoparticles, we find that dielectric ones are better choices to enhance a-Si thin-film solar cell absorption efficiency. Moreover, a composite light trapping structure with dielectric nanoparticles on the front surface and metal hemispheres on the rear surface is proposed to achieve broadband absorption enhancement in both short and long wavelengths, with the aim to get a higher conversion efficiency. The finite-difference-time-domain simulation results show that, compared with bare 100-nm-thick amorphous silicon solar cell, the short-circuit current density and photoelectric conversion efficiency could be respectively improved by 21% and 18% with addition of optimized composite light trapping structure. The general method proposed in this study could provide valuable guidance to light trapping structure design for various kinds of thin-film solar cells.

    关键词： Broadband absorption enhancement,Thin-film solar cell,Light trapping,Conversion efficiency,Amorphous silicon,Nanoparticle

    更新于2025-09-19 17:13:59

  • Visualizing different crystalline states during the infrared imaging of calcium phosphates

    摘要： Methods utilizing relatively simple mathematical operations during physical analyses to enable the visualization of otherwise invisible correlations and effects are of particular appeal to researchers and students in pedagogical settings. At the same time, discerning the amorphous phase from its crystalline counterpart in materials is challenging with the use of vibrational spectroscopy and is nowhere as straightforward as in phase composition analytical methods such as X-ray diffraction. A method is demonstrated for the use of first- and second-order differentiation of Fourier transform infrared spectra of calcium phosphates to distinguish their amorphous states from the crystalline ones based on the exact line positioning rather than on comparatively vaguer band broadening and splitting effects. The study utilizes a kinetic approach, focusing on the comparison of spectral features of amorphous precursors annealed in air at different temperatures or aged for different periods of time in an aqueous solution until transforming to one or a mixture of crystalline phases, including hydroxyapatite and α- and β-tricalcium phosphate. One of the findings challenges the concept of the nucleation lag time preceding the crystallization from amorphous precursors as a “dead” period and derives a finite degree of constructive changes occurring at the atomic scale in its course. The differential method for highlighting spectral differences depending on the sample crystallinity allows for monitoring in situ the process of conversion of the amorphous calcium phosphate phase to its crystalline analogue(s). One such method can be of practical significance for synthetic solid state chemists testing for the chemical stability and/or concentration of the reactive amorphous phase in these materials, but also for biologists measuring the maturity of bone and medical researchers evaluating its phase composition and, thus, the state of metabolic and mechanical stability.

    关键词： Hydroxyapatite,XRD,Derivative method,Crystallization,Amorphous,FTIR,Tricalcium phosphate

    更新于2025-09-19 17:13:59

  • Analysis of Processa??Dependent Electrical Properties of Silicon Heterojunction Solar Cells by Quantum Efficiency and Temperaturea??Dependent Current Densitya??Voltage Measurements

    摘要： Amorphous silicon–crystalline silicon (a-Si:H/c-Si) heterojunction solar cells are fabricated by infrared (IR) radiative or resistive preheating of silicon wafers before the a-Si:H layers deposition. The cells with IR radiative or resistive preheating lead to without S-shape (WoS) or with S-shape (WS) in their light current density–voltage (J–V) characteristics, respectively. The Suns-Voc analysis shows no front/back metal contact barriers for minority carriers in both cells. The light- and voltage-bias-dependent quantum efficiencies of the WS cell show the hindrance of carrier collection at the a-Si:H/c-Si interface due to the band offset, whereas more defective a-Si:H layers are observed in the WoS cell. The WS and WoS cells’ temperature-dependent dark J–V characteristics reveal that the carrier transport is through tunnel-assisted recombination and tunneling, respectively. The IR preheating of wafers results in the reduction of the bandgap of a-Si:H and facilitates for minimizing the band offset at the interface, whereas, the resistive heating shows the relatively better a-Si:H/c-Si interface passivation.

    关键词： S-shapes,heterojunctions,quantum efficiencies,amorphous silicon,band offsets,silicon solar cells

    更新于2025-09-19 17:13:59

  • Laser induced ultrafast combustion synthesis of solution-based AlO <sub/>x</sub> for thin film transistors

    摘要： Solution processing of amorphous metal oxides using excimer laser annealing (ELA) has been lately used as a viable option to implement large-area electronics, offering high quality materials at a reduced associated cost and process time. However, the research has been focused on semiconductor and transparent conductive oxide layers rather than on the insulator layer. In this work we present amorphous aluminum oxide (AlOx) thin films produced at low temperature (≤150 °C) via combustion synthesis triggered by ELA, for oxide thin film transistors (TFTs) suitable for manufacturing flexible electronics. The study showed that combining ELA and combustion synthesis leads to an improvement in the dielectric thin film’s densification in a shorter time (≤15 min). Optimized dielectric layers were obtained combining a short drying cycle at 150 °C followed by ELA treatment. High breakdown voltage (4 MV cm?1) and optimal dielectric constant (9) was attained. In general, TFT devices comprising the AlOx fabricated with a drying cycle of 15 min followed by ELA presented great TFT properties, a high saturation mobility (20.4 ± 0.9 cm2 V?1 s?1), a small subthreshold slope (0.10 ± 0.01 V dec?1) and a turn-on voltage ≈0 V. ELA is shown to provide excellent quality solution-based high-k AlOx dielectric, that surpass other methods, like hot plate annealing and deep ultraviolet (DUV) curing. The results achieved are promising and expected to be of high value to the printed electronic industry due to the ultra-fast film densification and the surface/area selective nature of ELA.

    关键词： thin film transistors,excimer laser annealing,solution processing,amorphous metal oxides,combustion synthesis,flexible electronics

    更新于2025-09-19 17:13:59

  • Raman study of laser-induced formation of IIa??VI nanocrystals in zinc-doped Asa??S(Se) films

    摘要： Zn-doped As2Se3 and As2S3 films were prepared by thermal evaporation. Their amorphous structure was confirmed by Raman spectroscopy. Zinc chalcogenide nanocrystals can be formed in the films under laser irradiation due to the photoenhanced diffusion of atoms in the arsenic chalcogenide films, which enables aggregation of Zn and S(Se) atoms in nanocrystals. For As2S3:Zn films, not only ZnS, but also ZnO crystallites can be formed under irradiation with UV laser light due to oxidation of the film surface with abundant zinc atoms.

    关键词： Raman scattering,Amorphous films,II–VI nanocrystals,Arsenic chalcogenides

    更新于2025-09-19 17:13:59

  • Enhanced Performance and Stability of Ternary Organic Solar Cells Utilizing Two Similar Structure Blend Fullerene‐Free Molecules as Electron Acceptor

    摘要： Two-dimensional amorphous semiconductor (2DAS) monolayers can be regarded as a new phase of 2D monolayers materials and will serve as a promising field for the various electronic and optoelectronic applications. Here, together with the first-principles calculations within density functional theory, we experimentally demonstrate that the 2DAS MoO3-x monolayers can enhance the electrochemical nitrogen reduction reaction (NRR). To be specific, the NH3 yield and faradaic efficiency (FE) reach 35.83 ug h-1 mg-1 cat at -0.40 V and 12.01 % at -0.20 V vs. reversible hydrogen electrode (RHE), respectively, and which can be dramatically improved than that of reported defective MoO3 nanosheets. Further theoretical calculations reveal that the high electrochemical performance in NH3 yield is contributed to the strong Anderson localization and electron confinement dimensionally. And such Anderson tail states can resonate effectively with the states of intermediate HNNH, playing the critical role in the rate limiting step of NRR. Integrated experimental findings and theoretical understanding, a new concept of Anderson confinement catalysis is put forward, and could be extended to other 2DAS for potential catalytic reactions.

    关键词： Anderson localization,amorphous,nitrogen reduction reaction,molybdenum oxides,supercritical CO2

    更新于2025-09-19 17:13:59