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Low Voltage Graphene-Based Amplitude Modulator for High Efficiency Terahertz Modulation
摘要： In this paper, a high-e?ciency terahertz amplitude modulation device based on a ?eld-e?ect transistor has been proposed. The polarization insensitive modulator is designed to achieve a maximum experimental modulation depth of about 53% within 5 V of gate voltages using monolayer graphene. Moreover, the manufacturing processes are inexpensive. Two methods are adopted to improve modulation performance. For one thing, the metal metamaterial designed can e?ectively enhance the electromagnetic ?eld near single-layer graphene and therefore greatly promote the graphene’s modulation ability in terahertz. For another, polyethylene oxide-based electrolytes (PEO:LiClO4) acts as a high-capacity donor, which makes it possible to dope single-layer graphene at a relatively low voltage.
关键词： solid electrolyte,terahertz,single-layer graphene,transmittance,metamaterial,amplitude modulation,?eld-e?ect transistor
更新于2025-09-23 15:21:01
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In Situ Raman Spectroscopy on Silicon Nanowire Anodes Integrated in Lithium Ion Batteries
摘要： Rapid decay of silicon anodes during lithiation poses a significant challenge in application of silicon as an anode material in lithium ion batteries. In situ Raman spectroscopy is a powerful method to study the relationship between structural and electrochemical data during electrode cycling and to allow the observation of amorphous as well as liquid and transient species in a battery cell. Herein, we present in situ Raman spectroscopy on high capacity electrode using uncoated and carbon-coated silicon nanowires during first lithiation and delithiation cycle in an optimized lithium ion battery setup and complement the results with operando X-ray reflection diffraction measurements. During lithiation, we were able to detect a new Raman signal at 1859 cm?1 especially on uncoated silicon nanowires. The detailed in situ Raman measurement of the first lithiation/delithiation cycle allowed to differentiate between morphology changes of the electrode as well as interphase formation from electrolyte components.
关键词： silicon nanowires,lithium ion batteries,in situ Raman spectroscopy,operando XRD,solid electrolyte interphase
更新于2025-09-19 17:15:36
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Nascent SEI-Surface Films on Single Crystalline Silicon Investigated by Scanning Electrochemical Microscopy
摘要： Silicon is a promising high capacity host material for negative electrodes in lithium-ion batteries with low potential for the lithiation/delithiation reaction that is outside the stability window of organic carbonate electrolytes. Thus, the use of such electrodes critically depends on the formation of a protective solid electrolyte interphase (SEI) from the decomposition products of electrolyte components. Due to the large volume change upon charging, exposure of the electrode material to the electrolyte must be expected, and facile re-formation of SEI is a scope for improving the stabilities of such electrodes. Here, we report the formation of incipient SEI layers on monocrystalline silicon by in-situ imaging of their passivating properties using scanning electrochemical microscopy after potentiodynamic charging to different final potentials. The images show a local initiation of the SEI growth at potentials of around 1.0 V vs. Li/Li+ in 1 M LiClO4 in propylene carbonate.
关键词： silicon electrode,single crystalline electrode,solid electrolyte interphase,scanning electrochemical microscopy,incremental charging
更新于2025-09-19 17:15:36
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Pyrochlore Ca-doped Gd2Zr2O7 solid state electrolyte type sensor coupled with ZnO sensing electrode for sensitive detection of HCHO
摘要： Solid state electrolyte type formaldehyde (HCHO) gas sensors based on a novel pyrochlore structure Gd2Zr2O7 solid electrolyte coupled with rod-shaped ZnO sensing electrode (SE) were initially designed and fabricated in this paper. The incorporation of alkaline-earth metal Ca can signi?cantly improve sensing performance of the Gd2Zr2O7 based sensors to HCHO. The response value (ΔV) of the sensors based on Gd2-xCaxZr2O7 (x = 0, 0.02, 0.05 and 0.1) varied approximately linear with the logarithm of HCHO concentration in the range of 1?100 ppm at 600 °C, with sensitivities of -25, -30, -15 and -5 mV/decade, respectively. The optimal sensor based on Gd1.98Ca0.02Zr2O7 (GCZ(0.02)) exhibited the excellent sensing characteristics with maximum response value (-61.3 mV) and extremely short response time (3 s) to 100 ppm HCHO. In addition, the GCZ(0.02) sensor also showed good selectivity and stability within 20-day period of continuous high-temperature aging under high-humidity condition. Conclusively, the sensing behavior and mechanism based on mixed potential were investigated and demonstrated by the mearsurement of the polarization curves.
关键词： Ca-doped Gd2Zr2O7,Rod-shaped ZnO,HCHO sensor,Pyrochlore solid electrolyte
更新于2025-09-19 17:13:59
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Organosoluble Starch-Cellulose Binary Polymer Blend as a Quasi-Solid Electrolyte in a Dye-Sensitized Solar Cell
摘要： This work is a pioneer attempt to fabricate quasi-solid dye-sensitized solar cell (QSDDSC) based on organosoluble starch derivative. Rheological characterizations of the PhSt-HEC blend based gels exhibited viscoelastic properties favorable for electrolyte fabrication. From amplitude sweep and tack test analyses, it was evident that the inclusion of LiI improved the rigidity and tack property of the gels. On the other hand, the opposite was true for TPAI based gels, which resulted in less rigid and tacky electrolytes. The crystallinity of the gels was found to decline with increasing amount of salt in both systems. The highest photoconversion e?ciency of 3.94% was recorded upon addition of 12.5 wt % TPAI and this value is one of the highest DSSC performance recorded for starch based electrolytes. From electrochemical impedance spectroscopy (EIS), it is deduced that the steric hindrance imposed by bulky cations aids in hindering recombination between photoanode and electrolyte.
关键词： dye-sensitized solar cell,phthaloyl starch,rheology,hydroxyethyl cellulose,quasi-solid electrolyte
更新于2025-09-16 10:30:52
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Organosoluble starch derivative as quasi-solid electrolytes in DSSC: Unravelling the synergy between electrolyte rheology and photovoltaic properties
摘要： A novel blend of organosoluble phthaloyl starch (PhSt) and hydroxyethyl cellulose (HEC) was used as the polymer host to fabricate polymer gel electrolytes. Rheological analyses, such as amplitude sweep studies and tack tests, indicate that gels with good rigidity, strength and adhesiveness were attained upon inclusion of 20 wt % of HEC onwards. However, beyond 60 wt% of HEC, the mechanical properties and ionic conductivity of the gels were considerably compromised. Gels comprising 20–60 wt% of HEC were then fabricated into quasi-solid dye-sensitised solar cells (QSDSSC) with the addition of tetrapropylammonium iodide/iodine. The highest efficiency of 3.02% was recorded with gels comprising 70 wt% of PhSt and 30 wt% of HEC, which to the best of our knowledge is the highest ever efficiency in literature for starch-based electrolytes. Electrochemical impedance spectroscopy (EIS) of the QSDSSC revealed that the adhesive property of the gels plays a crucial role in charge transfer processes at the electrode/electrolyte interfaces.
关键词： Rheology,Hydroxyethyl cellulose,Dye-sensitised solar cell,Quasi-solid electrolyte,Phthaloyl starch
更新于2025-09-16 10:30:52
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Solid State Succinonitrile/Sulfide Hole Transport Layer and Carbon Fabric Counter Electrode for a Quantum Dot Solar Cell
摘要： Solid-state quantum dot solar cell (QDSC) is implemented with cadmium sulfide (CdS) quantum dots (QDs) tethered to titanium oxide (TiO2) as photoanode, carbon fabric (C-fabric) as counter electrode (CE) and a solid electrolyte of succinonitrile/Na2S mixed in a 2:1 molar ratio (SN/S2-) is utilized as the hole transport material. Electron transfer and recombination processes are investigated by intensity modulated photocurrent spectroscopy (IMPS) and intensity modulated photovoltage spectroscopy (IMVS) for a TiO2/CdS/ZnS-SN/S2--C-fabric (solid-state) and TiO2/CdS/ZnS-S2--C-fabric (liquid junction) devices at different white light intensities. IMPS and IMVS studies show that the electron transport rate and electron recombination decrease with an increase in the intensity of light. The champion cell with a TiO2/CdS/ZnS photoanode and C-fabric as CE delivers a power conversion efficiency (PCE) of 5.2% with a solid electrolyte of SN/S2- and a PCE of 6.3% with is obtained with the liquid aqueous electrolyte of 0.1 M Na2S. Effect of temperature on solar cell performance and the thermal dependence of ionic conductivity for the solid electrolyte are studied in detail. This study shows that the succinonitrile based solid electrolyte is a good substitute for the traditional liquid electrolyte.
关键词： Solid electrolyte,quantum dots,succinonitrile,solar cells,carbon fabric
更新于2025-09-12 10:27:22
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European Microscopy Congress 2016: Proceedings || Direct mapping of Li-enabled octahedral tilt ordering and associated strain in nanostructured perovskites
摘要： Self-assembled nanostructures are promising for creating 2D and 3D superlattices with exceptional functionalities. Understanding the mechanisms driving the superlattice formation demands the underlying structural information. However, nanoscale structural modulations intrinsic to these superlattices are difficult to be characterized by conventional diffraction-based structure determination. A real-space, direct imaging method is necessary to probe the local structure characteristics, providing essential information for theoretical understanding and subsequent design of structure-property correlations. Using the aberration-corrected scanning transmission electron microscopy (STEM), we developed an optimized atomic-level bright-field (BF) condition to image the oxygen octahedra in perovskite oxides. We used multislice calculations to determine detector collection angles that allow oxygen octahedra to be imaged sensitively and robustly over large specimen thicknesses. These calculations also provided a calibration by which the octahedral-tilt angle can be measured quantitatively from the image of each octahedron. Applying this real-space octahedral-tilt mapping on Li0.5–3xNd0.5+xTiO3, a promising solid electrolyte in Li-ion batteries, we directly revealed an unconventional superlattices with 2D modulated octahedral tilting. A mathematical description of the octahedral-tilt modulation was derived based on the quantitative tilt maps, which explicitly identified the high-order harmonic character of the modulation. Using simultaneous annular-dark-field (ADF) imaging, we also mapped the lattice parameters unit-cell by unit-cell, uncovering highly-localized strain associated with the tilt modulation. Furthermore, we demonstrate the tunability of the tilt modulation by changing Li stoichiometry. Fascinatingly, we observe a reversible annihilation/reconstruction of the tilt modulation correlated with delithiation/lithiation process, suggesting the structural transformation that is associated with Li-ion conduction in this promising Li-ion conductor. The above observations are largely inaccessible from conventional diffraction analysis, and lead to an unprecedented mechanically-coupled tilting competition model to explain the superlattice formation. Our real-space approach to quantify local octahedral structure and correlate it with strain can be applied to other advanced oxide systems.
关键词： 2D modulated structure,STEM,Li-ion solid electrolyte,perovskite oxides,oxygen octahedral tilting
更新于2025-09-11 14:15:04
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Robust Pitch on Silicon Nanolayer-Embedded Graphite for Suppressing Undesirable Volume Expansion
摘要： A significant volume expansion exhibited by high-capacity active materials upon lithiation has hindered their application as Li-ion battery anode materials. Although tremendous progress has been made in the development of coating methods that improve the stability of high-capacity active materials, suitable coating sources that are both strong and economical to use are yet to be discovered. Pitch is reported here as a promising coating source for high-capacity anodes owing to the high mechanical strength and low-cost process. Using in situ transmission electron microscopy, it is found that pitch can withstand the severe volume expansion that occurs upon Si lithiation owing to its high mechanical strength, originating from the long-range graphitic ordering. Notably, pitch-coated silicon nanolayer–embedded graphite (SG) exhibits superior capacity retention (81.9%) compared to that of acetylene-coated SG (66%) over 200 cycles in a full-cell by effectively mitigating volume expansion, even under industrial electrode density conditions (1.6 g cc?1). Thus, this work presents new possibilities for the development of high-capacity anodes for industrial implementation.
关键词： volume expansion,Si anodes,lithium ion batteries,pitch,solid electrolyte interphase
更新于2025-09-10 09:29:36
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Effects of size on the phase stability and conductivity of double-doped δ-Bi2O3
摘要： Nano and micro (Bi2O3)1-x-y(Eu2O3)x(Er2O3)y (x = 0.1, 0.15, y = 0.05, 0.2) double-doped system materials are synthesized by exploiting solid-state synthesis techniques. When we use nano sized powders to synthesize the samples we call them nano; when we use micro sized powders, we call them micro. The thermal, structural, morphological and electrical properties of nano and micro structured electrolyte samples for solid oxide fuel cells (SOFCs) are characterized. As a result of XRD measurements, the face centered δ-Bi2O3 (cubic) phase is obtained for all nano samples. However, the mixed phase is obtained for some micro samples. The electrical measurements show that conductivity decreases when the amount of Er2O3 is increased. The principal conclusion of the study is that the size effect provides relatively good structural stability in intermediate temperature SOFCs (IT-SOFCs); also, the nano-Bi2O3 system has the lowest activation energy and demonstrates high electrical conductivity.
关键词： Solid electrolyte,IT-SOFC,Size effect,δ-Bi2O3,Nano-Bi2O3
更新于2025-09-10 09:29:36