Optical coatings on solar glass for photovoltaic modules and solar thermal collectors

Development of colored glazing for solar facades

Contact: Dr Andreas Schueler

Copenhagen International School waterfront view with colored solar cladding
Copenhagen International School, designed by C.F. Møller Architects & sits, solar façade designed by Danish company SolarLab with Kromatix technology developped by LESO-PB and Emirates Intersolaire (photo P. Vollichard)

Nanoporous silicon dioxide films exhibit a low refractive index suitable for broad band anti-reflection, and such coatings enter the market now. Nanocomposite quaternary Mg‑F‑Si‑O films exhibit also a low refractive index in the desired range, and might be more resistant regarding gradual pore-filling by hydrocarbons. Applying materials with a lower refractive index than silicon dioxide (refractive index approx. 1.46) allows for a larger spectral region of anti-reflection as compared to coatings based on materials with the refractive index equal or higher than that of silicon dioxide.

Nanocomposite Ti‑Si‑O films are used in novel multilayered coatings on solar glazing. Such coatings combine a colored reflection with a high solar transmittance and open new possibilities for the architectural integration of solar collectors in building facades. The optical performance of the multilayered interference filters is optimized by computer simulations of thin film interference. These interference filters manufactured by the sol-gel dip-coating process or magnetron sputtering techniques. Optical measurements, such as spectrophotometry or ellipsometry, are used to determine film thicknesses and optical constants of individual layers, and to measure color coordinates and solar transmission for the multilayer stacks. Nanostructured materials are tailored for maximizing the optical performance.

Based on this technology, our group has developed novel colored solar glazing for thermal collectors  and photovoltaic collectors for architectural integration into buildings. A convincing architectural integration of photovoltaic modules based on our technology has been achieved with the project of the Copenhagen International School – to our knowledge the building with the world’s largest photovoltaic façade today.

Two patents have been filed and are commercialised by SwissINSO:

WO 2014045141 A2: Laminated glazing with coloured reflection and high solar transmittance suitable for solar energy systems

WO 2014045144 A1: Interference filter with angular independent orange colour of reflection and high solar transmittance, suitable for roof-integration of solar energy systems



kromatix façade student experience Amsterdam Minerva
Student Experience Amsterdam Minerva, designed by VURB Architects, solar powered façade designed by Danish company SolarLab in collaboration with Pleijsierbouw and Solvis, with Kromatix technology developped by LESO-PB and Emirates Intersolaire (photo egbertdeboer.com)
acomet façade with coloured solar collectors
DOMA Solartechnik GmbH Headquarters, Satteins, Austria

In the media

HG-Gebäudetechnik 4/18: Fassadenintegration mit farbigen Oberflächen
24heures : La technologie de l’EPFL rayonne sur l’Ecole internationale de Copenhague
L’Agefi : Une technologie développée à l’EPFL recouvre une école entière
bulletin.ch : La plus grande façade solaire au monde
Le Matin du Dimanche: Grâce à Andreas Schueler l’énergie solaire se décline enfin en couleur  
smartcitiesworld.net : School claims largest solar façade in the world
greenbuildingelements.com : World’s Largest Solar Glass Envelope To Supply Electricity At Copenhagen International School
Daily Planet Blog: This Danish School has installed the World’s Largest Solar Facade
autocad-magazin.de : Architektur: Die Schule mit der weltgrößten Solarfassade | AUTO
bauen-aktuell.eu : Architektur: Die Schule mit der weltgrößten Solarfassade
energate messenger Schweiz : Schweizer Technologie macht dänische Solarfassade farbig
keest.ch : Schweizer Technologie ermöglicht farbige Solarfassade
Baublatt : In Kopenhagen treibt es eine Solaranlage bunt


V. Hody-Le Caër, E. De Chambrier, S. Mertin, M. Joly, M. Schaer, J.-L. Scartezzini, A. Schüler, Optical and morphological characterisation of low refractive index materials for coatings on solar collector glazing, Renewable Energy 53, 27-34 (2013) DOI:10.1016/j.renene.2012.10.052

S. Mertin, V. Hody-Le Caër, M. Joly, I. Mack, P. Oelhafen, J.-L. Scartezzini, A. Schüler, Reactively sputtered coatings on architectural glazing for coloured active solar thermal façades, (2014) Energy and Buildings, 68 (PART C), pp. 764-770.
DOI: 10.1016/j.enbuild.2012.12.030

S. Pélisset, M. Joly, V. Chapuis, A. Schüler, S. Mertin, V. Hody-Le Caër, C. Ballif, L.-E. Perret-Aebi, Efficiency of thin-film photovoltaic modules with a front coloured glass, Proceedings of the CISBAT International Scientific Conference 2011, Lausanne, Switzerland

A. Schüler, D. Dutta, E. de Chambrier, G. De Temmerman, P. Oelhafen, C. Roecker, J.-L. Scartezzini, Sol-gel deposition and optical characterization of multilayered SiO2/Ti1-xSixO2 coatings on solar collector glasses, Solar Energy Materials & Solar Cells 90, 2894 (2006)