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- Berggren, Lars, et al.
(författare)
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Electrical Conductivity as a Function of Temperature in Amorphous Lithium Tungsten Oxide
- 2004
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 84:1, s. 329-336
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten oxide is a widely used electrochromic material for smart windows. In order to study the charge carriers involved in the electrochromic process, it is important to characterize the electrical transport in tungsten oxide. Substoichiometric amorphous tungsten oxide films were prepared by DC-magnetron sputtering. The films were electrochemically intercalated with lithium. The Li/W intercalation ratios for the tungsten oxide films were in the range 0.15–0.53. Temperature dependent resistivity measurements were performed in the temperature range 77–300 K for samples at different lithium intercalation levels. It was found that the data are consistent with the variable range hopping model.
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| 3. |
- Ederth, Jesper, 1973-
(författare)
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Electrical Transport in Nanoparticle Thin Films of Gold and Indium Tin Oxide
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrical transport properties of nanoparticle gold films made by the gas evaporation method were analysed using resistivity measurements. Low temperature electrical transport measurements showed a cross-over from a temperature range dominated by inelastic scattering to a temperature range dominated by elastic scattering, presumably by grain boundaries. This cross-over shifted towards lower temperatures with increasing grain size. High temperature in-situ electrical transport measurements were carried out in isothermal annealing experiments. Four types of samples, prepared at different deposition rates, were analysed. Samples prepared at low deposition rate displayed a higher thermal stability than samples prepared at high deposition rate. A relaxation model was fitted to the in-situ electrical transport data. The model included an activation energy, which was found to increase with increasing annealing temperature for all samples, thus pointing at the presence of pinning mechanisms in the samples.Optical properties of nanoparticle gold films were investigated in the 0.3 < λ < 12.5 µm wavelength range. A model taking grain boundary scattering into account was successfully fitted to the experimental data and it was shown that the infrared reflectance decreased with decreasing grain size as a consequence of increased grain boundary scattering.Nanoparticle tin-doped indium oxide films were made by spin-coating a dispersion containing the nanoparticles onto a substrate. The tin-doped indium oxide particles were prepared by a wet-chemical method. Optical properties were investigated in the 0.3 < λ < 30 µm wavelength range by reflectance and transmittance measurements. Effective medium theory was employed in the analyses of the optical data and information regarding film porosity and charge carrier concentration and mobility within the individual nanoparticles was obtained. It was found that ionized impurity scattering of the conduction electrons dominates within the particles. The temperature-dependent film resistivity was found to be governed by insulating barriers between clusters containing a large number of nanoparticles, thereby giving a negative temperature coefficient of resistivity.
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| 7. |
- Gamage, Sampath, et al.
(författare)
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Transparent nanocellulose metamaterial enables controlled optical diffusion and radiative cooling
- 2020
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 8:34, s. 11687-11694
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Tidskriftsartikel (refereegranskat)abstract
- Materials that provide independent control of infrared thermal radiation and haze in the visible could benefit many areas and applications, including clothing, packaging and photovoltaics. Here, we study this possibility for a metamaterial composite paper based on cellulose nanofibrils (CNF) and silicon dioxide (SiO2) microparticles with infrared (IR) Fröhlich phonon resonances. This CNF-SiO2composite shows outstanding transparency in the visible wavelength range, with the option of controlling light diffusion and haze from almost zero to 90% by varying the SiO2microparticle concentration. We further show that the transparent metamaterial paper could maintain high thermal emissivity in the atmospheric IR window, as attributed to strong IR absorption of both the nanocellulose and the resonant SiO2microparticles. The high IR emissivity and low visible absorption make the paper suitable for passive radiative cooling and we demonstrate cooling of the paper to around 3 °C below ambient air temperature by exposing it to the sky.
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