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PERFORMANCE PREDICTION OF BUNDLE DOUBLE-WALLED CARBON NANOTUBE-COMPOSITE MATERIALS FOR DIPOLE ANTENNAS AT TERAHERTZ FREQUENCY RANGE
摘要： In this paper, the double-walled carbon nanotube composite material (DWCNTs-composite) and bundle of DWCNT-composite material (CB-DWCNTs) for antenna applications at terahertz frequency range are presented and investigated. The mathematical modeling and analysis of DWCNTs-composite material is presented for the purpose of modelling and simulation approach. The bundle of DWCNTs-composite material is constructed and designed, based on this modeling approach. The DWCNT-composite material consists of double-walled carbon nanotube coated by a thin jacket of another di?erent material. The dependency of the electrical conductivity of B-DWCNTs-composite on di?erent parameters is presented and investigated. The performance evaluation of B-DWCNTs-composite and CB-DWCNTs materials are presented based on their electromagnetic properties. For this purpose, the dipole antennas of these composite materials are designed and implemented using CST (MWS), where the cross sections of B-DWCNTs-composite and CB-DWCNT materials are circular geometry. Furthermore, comparative studies are performed to show the dependency of size and frequency of the DWCNT-composite material. The results obtained from the DWCNTs-composite and CB-DWCNTs dipole antennas are presented based on S11 parameters, resonant frequency, gain, bandwidth, and e?ciency.
关键词： terahertz frequency,dipole antennas,electromagnetic properties,composite material,double-walled carbon nanotube
更新于2025-09-23 15:19:57
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Light-Enhanced Ion Migration in Two-Dimensional Perovskite Single Crystals Revealed in Carbon Nanotubes/Two-Dimensional Perovskite Heterostructure and Its Photomemory Application
摘要： Two-dimensional (2D) hybrid perovskite sandwiched between two long-chain organic layers is an emerging class of low-cost semiconductor materials with unique optical properties and improved moisture stability. Unlike conventional semiconductors, ion migration in perovskite is a unique phenomenon possibly responsible for long carrier lifetime, current?voltage hysteresis, and low-frequency giant dielectric response. While there are many studies of ion migration in bulk hybrid perovskite, not much is known for its 2D counterparts, especially for ion migration induced by light excitation. Here, we construct an exfoliated 2D perovskite/carbon nanotube (CNT) heterostructure field effect transistor (FET), not only to demonstrate its potential in photomemory applications, but also to study the light induced ion migration mechanisms. We show that the FET I?V characteristic curve can be regulated by light and shows two opposite trends under different CNT oxygen doping conditions. Our temperature-dependent study indicates that the change in the I?V curve is probably caused by ion redistribution in the 2D hybrid perovskite. The first principle calculation shows the reduction of the migration barrier of I vacancy under light excitation. The device simulation shows that the increase of 2D hybrid perovskite dielectric constant (enabled by the increased ion migration) can change the I?V curve in the trends observed experimentally. Finally, the so synthesized FET shows the multilevel photomemory function. Our work shows that not only we could understand the unique ion migration behavior in 2D hybrid perovskite, it might also be used for many future memory function related applications not realizable in traditional semiconductors.
关键词： photomemory,carbon nanotube,ion migration,Two-dimensional perovskite,heterostructure
更新于2025-09-23 15:19:57
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Immobilization of C/Ce-codoped ZnO nanoparticles on multi-walled carbon nanotubes for enhancing their photocatalytic activity
摘要： C/Ce-codoped ZnO nanoparticles immobilized onto multi-walled carbon nanotubes (C/Ce-ZnO@MWCNT) were successfully fabricated via the hydrothermal method for degradation of methylene blue (MB) under visible light irradiation. The prepared C/Ce-ZnO@MWCNT samples were characterized by XRD, XPS, FTIR, FE-SEM, EDX, BET, and diffuse reflectance spectroscopy. The obtained results indicated that the photocatalytic activity of all the MWCNTs-containing samples was higher than those of the bare ZnO and C/Ce-codoped ZnO nanoparticles. Besides, the C/Ce-ZnO@MWCNT composite with 50 wt% MWCNT showed the highest photocatalytic activity with the MB removal efficiency of 96.5% recorded within 90 min under visible light illumination using 1.0 g/L catalyst dosage at pH of 9 and MB concentration of 30 ppm. The degradation mechanism controlled by the charge transfer process in C/Ce-ZnO@MWCNT composite was proposed and discussed in detail. In addition, the long-term-use ability of the photocatalyst was also evaluated through experiments conducted in continuous cycles.
关键词： visible light,C/Ce-ZnO@MWCNT,photocatalytic activity,multi-walled carbon nanotube,methylene blue
更新于2025-09-23 15:19:57
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Improving CNT-Si solar cells by metal chloride-to-oxide transformation
摘要： Transitional metal oxides (TMOs) are important functional materials in silicon-based and thin-film optoelectronics. Here, TMOs are applied in carbon nanotube (CNT)-Si solar cells by spin-coating solutions of metal chlorides that undergo favorable transformation in ambient conditions. An unconventional change in solar cell behavior is observed after coating two particular chlorides (MoCl5 and WCl6, respectively), characterized by an initial severe degradation followed by gradual recovery and then well surpassing the original performance. Detailed analysis reveals that the formation of corresponding oxides (MoO3 and WO3) enables two primary functions on both CNTs (p-type doping) and Si (inducing inversion layer), leading to significant improvement in open-circuit voltage and fill factor, with power conversion efficiencies up to 13.0% (MoO3) and 13.4% (WO3). Further combining with other chlorides to increase the short-circuit current, ultimate cells efficiencies achieve >16% with over 90% retention after 24 h, which are among the highest stable efficiencies reported for CNT-Si solar cells. The transformation of functional layers as demonstrated here has profound influence on the device characteristics, and represents a potential strategy in low-cost manufacturing of next-generation high efficiency photovoltaics.
关键词： carbon nanotube (CNT)-Si solar cell,inversion layer,chloride to oxide transformation,MoO3 and WO3
更新于2025-09-23 15:19:57
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Fabrication of nickel oxide composites with carbon nanotubes for enhanced charge transport in planar perovskite solar cells
摘要： As the conductivity of metal oxides is often insufficient for use in inverted planar perovskite solar cells (PSCs), a hybrid hole transporter consisting of carbon nanotube (CNT)-embedded nickel oxide (NiOx) is suggested to enhance the conductivity. Fully solution-processed NiOx/CNT composites are prepared by introducing CNTs (0–20 vol.%) into a NiOx solution. Raman spectroscopy confirms successful incorporation of the CNTs in the NiOx-based hybrid material. Also, enhanced conductivity of NiOx by introducing CNTs is confirmed by conductance measurement and conductive atomic force microscopy. Furthermore, the enhanced charge extraction properties of the NiOx/CNTs hybrid are evidenced by transient photocurrent, steady-state and time-resolved photoluminescence. Electrochemical impedance spectroscopy reveals a reduction in charge recombination when the hybrid material is used as the hole transport layer (HTL) in PSCs. Interestingly, the average power conversion efficiency (PCE) of the PSCs is increased from 13.1% to 15.1% by applying this hybrid HTL. The best-performing cell, using NiOx/CNTs (7.5 vol.%), exhibits a PCE of up to 16.9%. This unprecedented HTL provides a fundamental method for enhancing the performance of inorganic charge transporters for solution-processed inverted planar PSCs.
关键词： carbon nanotube,perovskite,solar cell,charge transport,nickel oxide
更新于2025-09-23 15:19:57
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Synthesis of diameter controlled multiwall carbon nanotubes by microwave plasma-CVD on low-temperature and chemically processed Fe nanoparticle catalysts
摘要： Properties of carbon nanotubes sensitively depend on the structural configuration, e.g., chirality, diameter, layer number and the compositional characteristics. The size of catalyst nanoparticles used to grow the CNTs significantly controls its diameter. Generally, catalyst nanoparticles are size-optimized via high-temperature annealing of thin metal films. Presently, formation of size-controlled Fe nano-particles as the efficient catalyst has been pursued via a low-temperature (TCG) wet chemical process that bypasses the high-temperature annealing step and leads to a low average size of catalyst nanoparticles. Suitable progress of the oxidation–hydrolysis reactions of metal-bearing ferrite entities controls the crystallinity via dehydration of the intermediate constituent and diminution of the oxide component. Optimally low diameter Fe nanoparticles have been obtained at temperature around TCG ~ +10 °C via simultaneous prominent aerial oxidation and neutralization in a single step. In this present work multiwall carbon nanotubes of controlled diameter (~15–25 nm) have been produced by relatively low-temperature (~300 °C) plasma processing, using pre-designed shadow-mask assembly to create diffused and remote-plasma of (CH4 + H2) and CO2 as a weak oxidizing gas to selectively remove the surplus amorphous components, and also by controlling the size of catalyst Fe-nanoparticles on the substrate via low-temperature non-plasma synthesis process.
关键词： Carbon nanotube,Fe-nanoparticle synthesis,Diameter controlled growth,2.54 GHz microwave plasma,Raman scattering
更新于2025-09-23 15:19:57
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Thermocells for Hybrid Photovoltaic/Thermal Systems
摘要： The photovoltaic conversion e?ciency of solar cells is highly temperature dependent and decreases with increasing temperature. Therefore, the thermal management of solar cells is crucial for the e?cient utilization of solar energy. We fabricate a hybrid photovoltaic/thermocell (PV/T) module by integrating a thermocell directly into the back of a solar panel and explore the feasibility of the module for its practical implementation. The proposed PV/T hybrid not only performs the cooling of the solar cells but also produces an additional power output by converting the heat stored in the solar cell into useful electric energy through the thermocell. Under illumination with an air mass of 1.5 G, the conversion e?ciency of the solar cell can improve from 13.2% to 15% by cooling the solar cell from 61 ?C to 34 ?C and simultaneously obtaining an additional power of 3.53 μW/cm2 from the thermocell. The advantages of the PV/T module presented in this work, such as the additional power generation from the thermocell as well as the simultaneous cooling of the solar cells and its convenient installation, can lead to the module’s importance in practical and large-scale deployment.
关键词： photovoltaic,carbon nanotube,ferric/ferrous cyanide,thermal management,thermocell
更新于2025-09-23 15:19:57
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A flexible and ultra-broadband terahertz wave absorber based on graphenea??vertically aligned carbon nanotube hybrids
摘要： Electromagnetic wave absorbers are essential devices in imaging, wireless communication and energy harvesting systems. In this paper, we propose and experimentally demonstrate a flexible and ultra-broadband terahertz (THz) wave absorber based on graphene-vertically aligned carbon nanotube (G-VACNT) hybrids. The THz absorber consists of Cu/PDMS/graphene/VACNT functional layers on PET substrate. Measured results show a 100% qualified operating bandwidth (i.e., absorptance >0.9) and an average power absorptance of 0.986 within the 0.2-3.0 THz range. The absorber also exhibits good absorption performances for a wide range of incident angles up to 60°, and can function normally in different bending states due to its excellent flexibility. The incoming energy of THz waves absorbed by the G-VACNT hybrids results in a temperature increase whose spatial distribution is corresponding to the profile of incident THz beam, providing an efficient and low cost approach for THz beam profiling, collimation and focusing. This work paves the way for the development of large-scale and broadband THz wave absorbers.
关键词： Vertically aligned carbon nanotube,Ultra-broadband,Graphene,Flexible,Terahertz wave absorber
更新于2025-09-23 15:19:57
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Combined solar concentration and carbon nanotube absorber for high performance solar thermoelectric generators
摘要： Solar thermoelectric generators (STEGs) is one of the most important technologies for solar energy conversion. However, the inefficiency due to coupling constraints such like low working temperature and dimensionless figure of merit of the thermoelectric materials, also known as material’s ZT value, has been hampering the development of STEGs for a time. Here we demonstrate a high performance STEG system combined with solar concentrators and carbon nanotubes (CNTs) absorber, which can greatly improve the solar-thermal conversion process. The proposed STEG system enables a peak efficiency of 4.3% with solar concentration of 78, and a maximum power of 11.2 W at 106× suns. The enhanced efficiency is ensured by the optimized system thermodynamics due to the combination of solar concentration devices and CNT based solar absorber. Our design provides a universal prototype of solar thermal energy recovery system for distributed energy harvesting and deep-space explorations.
关键词： Thermodynamics,Carbon nanotube,Solar concentration,Thermoelectricity,Energy harvesting
更新于2025-09-19 17:15:36
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Electronic transport through defective semiconducting carbon nanotubes
摘要： We investigate the electronic transport properties of semiconducting (m, n) carbon nanotubes (CNTs) on the mesoscopic length scale with arbitrarily distributed realistic defects. The study is done by performing quantum transport calculations based on recursive Green’s function techniques and an underlying density-functional-based tight-binding model for the description of the electronic structure. Zigzag CNTs as well as chiral CNTs of different diameter are considered. Different defects are exemplarily represented by monovacancies and divacancies. We show the energy-dependent transmission and the temperature-dependent conductance as a function of the number of defects. In the limit of many defetcs, the transport is described by strong localization. Corresponding localization lengths are calculated (energy dependent and temperature dependent) and systematically compared for a large number of CNTs. It is shown, that a distinction by (m ? n)mod 3 has to be drawn in order to classify CNTs with different bandgaps. Besides this, the localization length for a given defect probability per unit cell depends linearly on the CNT diameter, but not on the CNT chirality. Finally, elastic mean free paths in the diffusive regime are computed for the limit of few defects, yielding qualitatively same statements.
关键词： defect,electronic transport,density-functional-based tight binding (DFTB),Carbon nanotube (CNT),recursive Green?s function formalism (RGF),strong localization,elastic mean free path
更新于2025-09-19 17:15:36