1,721,316 research outputs found
Enhanced triboelectrification of the polydimethylsiloxane surface by ultraviolet irradiation
No full textStudy of the triboelectric charging effect has recently gained much attraction by proposing a new potential technical application in the field of energy harvesting. Transparent polydimethylsiloxane (PDMS) has some advantages in employing the triboelectric effect due to good conformity at nanometer scale and the simple fabrication process. In this study, we demonstrate that UV irradiation can enhance the performance of a PDMS-based nanotribogenerator. Contact atomic force microscopy combined with Kelvin probe force microscopy enables an in-depth investigation of the effect of UV illumination on local triboelectric charge generation and its decay in PDMS. We found that UV exposure not only facilitates triboelectric charge generation but also enhances charge redistribution, which is related to the wettability of the PDMS surface. This study provides insights into the fundamental understanding and design of triboelectric generator devices. © 2016 AIP Publishing LLC22
Nanomechanical and Charge Transport Properties of Two-Dimensional Atomic Sheets
No full textThe materials properties of graphene and other two-dimensional atomic sheets are influenced by atomic-scale defects, mechanical deformation, and microstructures. Thus, for graphene-based applications, it is essential to uncover the roles of atomic-scale defects and domain structures of two-dimensional layers in charge transport properties. This review highlights recent studies of nanomechanical and charge transport properties of two-dimensional atomic sheets, including graphene, MoS2, and boron nitrides. Because of intrinsic structural differences, two-dimensional atomic sheets give rise to unique nanomechanical properties, including a dependence on layer thickness and chemical modification that is in contrast to three-dimensional continuum media. Mapping of local conductance and nanomechanical properties on a graphene layer can be used to image the domain and microstructures of two-dimensional atomic layers. This paper also reviews recent experimental and theoretical findings on the role of bending, defects, and microstructures on nanomechanical and transport properties of graphene-derived materials.113151scopu
Enhancing the Internal Quantum Efficiency and Stability of Organic Solar Cells via Metallic Nanofunnels
No full textMetal nanoparticles are demonstrated to boost the internal quantum efficiency (IQE) of organic solar cells (OSCs), even without a notable plasmonic optical gain. A hybrid layer platform in combination with silver nanoparticles (AgNPs) and a polyethylenimine-ethoxylated (PEIE) layer maximize the IQE of the OSCs to nearly 100%, yielding a power conversion efficiency (PCE) of 10.1% in the OSCs. 2D surface characterization confirmed that the AgNPs provide a short path and funneled charge carriers to the cathode, thus effectively increasing the carrier mobility. Moreover, the hybrid layer doubles the device's half-efficiency lifetime due to the longer retention of the improved mobility. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim172011sciescopu
Impact of Water Corrosion on Nanoscale Conductance on Aluminum Doped Zinc Oxide
No full textOne major cause of failure in solar cell modules is associated with the degradation of conductive layers by the ingress of water. In this study, the corrosive interactions between water and transparent conducting oxides, including aluminum-doped ZnO (AZO) and indium tin oxide (ITO), were studied. The AZO layer exhibited -90% increase in sheet resistance from 17.5 to 33 ohm/square after an accelerated moisture test where the samples were stored at 80 degrees C and 100% humidity, while the conductivity of the ITO layer remained essentially unchanged. In order to elucidate the water-induced degradation mechanism of AZO, the structure and composition were characterized with conductive atomic force microscopy, energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS) before and after the moisture test. It was found that the grain boundary of AZO exhibits a higher local conductance compared to that in the middle of the grain. A decrease in local conductance at the grain boundary after the moisture test was observed, which is attributed to depletion of the Zn, based on XPS and EDS analyses.1881sciescopu
Work function variation of MoS2 atomic layers grown with chemical vapor deposition: The effects of thickness and the adsorption of water/oxygen molecules
Get PDFThe electrical properties of two-dimensional atomic sheets exhibit remarkable dependences on
layer thickness and surface chemistry. Here, we investigated the variation of the work function
properties of MoS2 films prepared with chemical vapor deposition (CVD) on SiO2 substrates with
the number of film layers. Wafer-scale CVD MoS2 films with 2, 4, and 12 layers were fabricated
on SiO2, and their properties were evaluated by using Raman and photoluminescence spectroscopies.
In accordance with our X-ray photoelectron spectroscopy results, our Kelvin probe force microscopy
investigation found that the surface potential of the MoS2 films increases by 0.15 eV
when the number of layers is increased from 2 to 12. Photoemission spectroscopy (PES) with insitu
annealing under ultra high vacuum conditions was used to directly demonstrate that this work
function shift is associated with the screening effects of oxygen or water molecules adsorbed on the
film surface. After annealing, it was found with PES that the surface potential decreases by
0.2 eV upon the removal of the adsorbed layers, which confirms that adsorbed species have a role
in the variation in the work function © 2015 AIP Publishing LLC141471sciescopu
Transfer-printable micropatterned fluoropolymer-based triboelectric nanogenerator
No full textTriboelectric nanogenerators (TENG) are increasingly considered as a promising energy harvesting system due to high output performance from various wasted energy sources. Numerous studies addressing the TENG configuration improve the performance of these devices by optimizing the paired triboelectric materials and structural geometry. Here, poly(1H,1H,2H,2H-perfluorodecyl methacrylate) (PFDMA) fluoropolymer is adopted as a novel negative tribo-material for application to a TENG, as it is at the topmost negative position of the triboelectric series and it is possible to tune the surface roughness under mild conditions. The intrinsic properties are examined and systematic measurements are carried out with the goal of applying the material to a TENG. PFDMA is suitable for application to a TENG, because PFDMA-TENG exhibits a high voltage, current, and power density of 68 V, 6.68 μA, and 150 μW, respectively, under a load of 500 MΩ. Moreover, a PFDMA film offers two distinctive advantages making it ideal for application to a TENG: transmittance higher than 98% even with a relatively high surface roughness, and transfer printing on diverse substrates. The results indicate that PFDMA is a novel negative tribo-material candidate for the fabrication of a TENG with superior triboelectric performance by controlling the surface charge density and morphology. © 2017 Elsevier Lt5
Bimodal Control of Heat Transport at Graphene–Metal Interfaces Using Disorder in Graphene
Get PDFThermal energy transport across the interfaces of physically and chemically modified graphene
with two metals, Al and Cu, was investigated by measuring thermal conductance using the timedomain
thermoreflectance method. Graphene was processed using a He2+ ion-beam with a Gaussian
distribution or by exposure to ultraviolet/O3, which generates structural or chemical disorder,
respectively. Hereby, we could monitor changes in the thermal conductance in response to varying
degrees of disorder. We find that the measured conductance increases as the density of the physical
disorder increases, but undergoes an abrupt modulation with increasing degrees of chemical
modification, which decreases at first and then increases considerably. Moreover, we find that the
conductance varies inverse proportionally to the average distance between the structural defects in the
graphene, implying a strong in-plane influence of phonon kinetics on interfacial heat flow. We attribute
the bimodal results to an interplay between the distinct effects on graphene’s vibrational modes
exerted by graphene modification and by the scattering of modes.
© The Author(s) 20161
Crossing Thermal Lubricity and Electronic Effects in Friction: Vanadium Dioxide under the Metal-Insulator Transition
No full textThe remarkable turnover of friction on a vanadium dioxide (VO2) surface driven by the metal-insulator transition is revealed using temperature-variable atomic force microscopy in ultrahigh vacuum. Phononic and electronic contributions are known as two major components in mediating friction energy dissipation. Here, a VO2 thin film is prepared on a silicon wafer with preferential orientations of (100) and (120) in the monoclinic phase using pulsed laser deposition. Corresponding friction and conductivity images show that friction decreases below the critical temperature, above which two trends are seen as the temperature increases: less friction on the insulating domains and higher friction on the metallic domains. This distinct temperature dependence of friction is attributed to the combined effects of thermal lubricity and electronic contributions. This study indicates the promising potential for vanadium oxide to tune friction in the electric regime as well as with temperature. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim11sciescopu
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