Papers by Author: Claes Goran Granqvist

Abstract: Chromogenic materials and devices allow the construction of glazings whose throughput of visible light and solar energy can be varied depending on the application of an electrical voltage or temperature. These glazings are of much interest for energy efficient buildings and are able to create energy efficiency along with indoor comfort. This paper outlines the basics of electrochromic and thermochromic technologies with foci on functional principles, materials, device and manufacturing technology, and selected results from research and development.

Abstract: Thin films of Au were made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films were up to ~11 nm in thickness and covered the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less “holey” film. Scanning electron microscopy and atomic force microscopy showed that the SnO2:In films were considerably rougher than the glass itself. This roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and electrical resistance could be reconciled with impeded Au film formation on the SnO2:In layer, leading to pronounced “plateaus” in the near infrared optical properties for Au films on SnO2:In and an accompanying change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses.

Abstract: 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.

Abstract: Electrochromic (EC) device technology can be used for modulating the transmittance of visible light and solar radiation in windows in buildings as well as for other see-through applications. This paper emphasizes the great energy savings that can be achieved in the built environment, jointly with improved indoor comfort for the users of the building. Manufacturing aspects are considered with particular focus on potentially low-cost methods possible to implement with roll-to-roll technology. In particular the paper discusses recent work on foil-type devices embodying sputter deposited WO3 and NiO-based films joined by a polymer electrolyte.