Claes-Göran Granqvist

Bio: Claes-Göran Granqvist is an academic researcher from Uppsala University. The author has contributed to research in topics: Electrochromism & Thin film. The author has an hindex of 73, co-authored 535 publications receiving 31523 citations. Previous affiliations of Claes-Göran Granqvist include Chalmers University of Technology & Texas A&M University.

Nickel pigmented anodic aluminum oxide for selective absorption of solar energy

Abstract: Spectrally selective surfaces on Al metal sheets were prepared by dc anodization in dilute phosphoric acid followed by black coloration via ac electrolysis in a bath containing NiSO4. These coatings had good durability, as found from several accelerated tests. The optical performance was studied by the recording of hemispherical reflectance or specular reflectance in conjunction with diffuse light scattering. From these results we extracted a solar absorptance of 0.93–0.96 and a corresponding thermal emittance of 0.10–0.20. The structure of the coatings was investigated by scanning electron microscopy on fractured specimens, Auger electron spectroscopy combined with depth profiling by sputtering, and atomic absorption analysis. Based on this information, a multilayer model was formulated, its most conspicuous feature being a sheath near to the Al interface comprised of metallic Ni particles in an Al2O3 matrix. The optical properties of this layer were described either by the Maxwell Garnett theory or the ...

Advances in Chromogenic Materials and Devices

Abstract: Abstract Chromogenic materials allow the transmittance of visible light and solar energy to be varied under the action of an external stimulus. This paper first discusses buildings related energy savings that can be accomplished by chromogenic technologies, and their beneficial effects on comfort issues. We then summarize recent work on thermochromic VO 2 -based thin films with particular attention to multi-layers of VO 2 and TiO 2 and to new VO 2 :Mg films for which the doping gives significantly lowered absorption of visible light. The final part covers electrochromic materials and devices with foci on coloration efficiency and on durability issues for foil-type constructions based on films of WO 3 and NiO.

Thermochromic VO2‐based multilayer films with enhanced luminous transmittance and solar modulation

Abstract: Vanadium dioxide (VO2) shows an abrupt and reversible change in optical and electrical properties when the temperature is raised beyond a critical point of similar to 68 degrees C. Films made from this material have a potential to be used in energy efficient "smart" windows with temperature-dependent throughput of solar radiation. Two of the drawbacks of this material have been its low luminous transmittance and limited solar modulation of transmittance during switching. In this work we report calculations and experiments on multilayers Of VO2 and TiO2, produced by reactive DC magnetron sputtering, that significantly improve the luminous transmittance and solar modulation of the films during switching. We also explore the angular-dependent transmittance of five-layer TiO2/VO2/TiO2/VO2/TiO2 films and demonstrate that the modulation of luminous and solar transmittance can be enhanced at non-normal angles of incidence.

Graphene photonics and optoelectronics

Abstract: The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light-emitting devices to touch screens, photodetectors and ultrafast lasers. Here we review the state-of-the-art in this emerging field.