Browsing by Author "Li, S.-Y."

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    Band gap widening in thermochromic Mg-doped VO2 thin films: Quantitative data based on optical
    (2013-10) Li, S.-Y.; Mlyuka, N.R.; Primetzhofer, Daniel; Hallén, Anders; Possnert, Goran; Niklasson, Gunnar A.; Granqvist, C. G.
    hermochromic Mg-doped VO2 films were deposited by reactive DC magnetron sputtering onto heated glass and carbon substrates. Elemental compositions were inferred from Rutherford backscattering. Optical band gaps were obtained from spectral transmittance and reflectance measurements—from both the film side and the back side of the samples—and ensuing determination of absorption coefficients. The band gap of Mg-doped films was found to increase by 3.6 ± 0.6 eV per unit of atom ratio Mg/(Mg + V) for 0 < Mg/(Mg + V) < 0.21. The presence of ~0.45 at.% Si enhanced the band gap even more.
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    Chromogenics for Sustainable Energy: Some Advances in Thermochromics and Electrochromics
    (2010-10) Granqvist, C. G.; Green, Sara V.; Li, S.-Y.; Mlyuka, N.R.; Niklasson, Gunnar A.; Avendaño, E.
    Chromogenic materials are able to change their optical properties in response to external stimuli such as temperature (in thermochromic materials) and electrical charge insertion (in electrochromic materials). Below we review some recent advances for these types of materials. Specifically we first discuss the limitations of thermochromic VO2 films for energy efficient fenestration and show from calculations that nanocomposites containing VO2 can have superior properties and display high luminous transmittance and large temperature-dependent solar transmittance modulation. Even better results may be found for nanoparticles of VO2:Mg. In the second part of the paper we survey some recent progress for electrochromic devices and show that W oxide films have increased coloration efficiency when some Ni oxide is added. We also present initial results for flexible electrochromic foils produced by roll-to-roll coating and continuous lamination.