Nanotechnology for Solar Energy Conversion

Due to their fascinating optical and electronical properties, nanometer-scaled structures play an important role in solar energy conversion. In our research group, we develop novel micro- and nanostructured smart materials for active and passive solar energy applications being integrated into the building envelope. We focus on thin films, because these allow covering a large surface area with a small quantity of raw material – and we focus on their electronic and optical properties, because these closely interrelated properties are most important for the utilisation of solar energy.

Nanocomposite coatings consist typically of dielectric, semiconductor or metal nanocrystals being embedded in a dielectric matrix. Effective medium theories such as the Bruggeman and the Ping Sheng theory are used to model the dielectric function of nanocomposite materials. The method of finite differences in the time domain (FDTD) allows nowadays to simulate the interaction of light with complex structures on the micrometric and nanometric scale. Micro- and/or nanostructuring materials can result in very interesting features such as tunable band-gaps by quantum confinement, adjustable complex dielectric function, enhanced mechanical stability, superhydrophobicity, frequency-selective surfaces FSS [BOU2017], etc. The semiconductor-to-metal transition observed in transition metal oxides with strong electron correlations can be exploited for smart switching coatings [KRA2017].

Our unique and specifically designed experimental infrastructure allows us the plasma-deposition of novel nanocomposite thin films and the subsequent characterization of their electronic properties by photoelectron spectroscopies (XPS & UPS). Recently we have added surface characterization with nanometric lateral resolution by scanning tunnelling microscopy (STM) and spectroscopy (STS). Using these methods, we determine features such as the alignment of valence and conduction band edges at an interface of a heterostructure, the difference in workfunction leading to a built-in electrostatic field, band bending at surfaces and interfaces as well as local variations of the energy gap in polycrystalline films. Because the above-mentioned characterization techniques are very surface sensitive, it is a crucial advantage that the deposited thin films can be analysed in-line without breaking the vacuum.  We synthesise new materials, create novel micro- and nanostructures, study the occurring physical phenomena, and tailor the systems to the targeted solar energy applications.   

The scope of envisaged solar energy applications is large. Recent work focuses especially on smart materials, such as thermochromic selective solar absorber coatings for overheating protection of solar thermal systems [KRA2022a], and electrochromic coatings for switchable windows [BOU2021], [FLE2022], [FLE2023]. Further applications include microstructured glazing with strong seasonal dependence of the solar heat gains [GON2018], photoluminescent quantum dot solar concentrators for photovoltaic energy conversion, antireflection coatings on solar collector glazing, colored coatings with high solar transmittance for novel glazing of photovoltaic facades [JOL2017], selective solar absorber coatings for thermal solar collectors and thermoelectric power generation [KRA2022b], fuel cells [NI2023], microelectronics [NIK2022], as well as novel insulating glazing with high transmittance for the microwaves of mobile communication [FLE2020].

Our lab equipment | Publications | Patents | Awards | PhD theses

Research topics

• Smart selective solar absorber coatings based on reversible semiconductor-to-metal transition
• Solid-ion-conductors for durable electrochromic windows
• Metallic micro-/nanomeshes for transparent conductive layers
• Highly durable selective solar absorber coatings for solar thermal collectors and electricity generation by concentrated solar power (CSP)
• Frequency-selective surfaces by nanosecond laser-ablation
• Optical coatings on solar glass for photovoltaic modules and solar thermal collectors – development of colored glazing for solar facades and solar roofing
• Energy efficiency of public transportation
• Quantum dot solar concentrators for building integrated photovoltaics
• Angular dependent optical and thermal properties of advanced architectural glazing
• Optical microstructures for advanced architectural glazing
• Building integration of our novel solar technologies

 

Patents

WO2017134589 (A1) : Coating for optical and electronic applications – Single- or multilayered coating, such as a selective solar absorber coating or a coating being part of an integrated electronic circuit, comprising one or more layers containing germanium (Ge) doped VO2+x, where -0.1 ≤ x ≤ 0.1.
Krammer Anna, Paone Antonio, Schüler Andreas

PCT/IB2017/051952: Solar cooker
Mauree Dasaraden, Schueler Andreas, Diévart Alexandre, Bouvard Olivia

WO2014024146  EP2882921 – Glazing with embedded microstructures for daylighting and seasonal thermal control,
Kostro André, Schüler Andreas

WO 2014045141 A2: Laminated glazing with coloured reflection and high solar transmittance suitable for solar energy systems
Le Caër Hody Virginie, Schüler Andreas (Déposant SwissInso SA)

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

www.glassdbase.ch – an independent and comprehensive building glass database set up by University of Basel, Switzerland and now managed by LESO-PB

PhD Theses

J. Fleury, Scartezzini Jean-Louis and Schueler Andreas (Dirs.). Transparent structured conductive coating for applications in smart windows, EPFL PhD thesis No. 10029 (2023)

Anna Krammer, Scartezzini Jean-Louis and Schueler Andreas (Dirs.).Doping of thermochromic oxide coatings for overheating protection of solar thermal collectors, EPFL PhD thesis No. 7625 (2020)

Jing Gong, Scartezzini Jean-Louis and Schueler Andreas (Dirs.). Glazing with novel embedded optical microstructures for seasonal thermal dynamics, daylighting, glare protection and clear view, in various locations and climates, EPFL PhD Thesis No. 9390 (2019)

Olivia Bouvard, Scartezzini Jean-Louis and Schueler Andreas (Dirs.). Coatings with tailored electronic and optical properties for advanced glazing. EPFL Thesis n° 9199 (2019)

A. G. Kostro, J.-L. Scartezzini and A. Schueler (Dirs.). Microstructured glazing for daylighting, glare protection, seasonal thermal control and clear view. EPFL PhD thesis, n° 6465 (2015)

A. Paone, J.-L. Scartezzini and A. Schueler (Dirs.). Switchable Selective Absorber Coatings for Overheating Protection of Solar Thermal Collectors. EPFL PhD thesis, n° 5878 (2013)

M. Joly, J.-L. Scartezzini and A. Schueler (Dirs.). Développement et optimisation de revêtements minces nanostructurés pour capteurs solaires thermiques et modules photovoltaïques. EPFL PhD thesis, n° 5541 (2012).

Awards

RailTech 2019 Innovation Award, Utrecht, to Andreas Schüler, Olivia Bouvard, Luc Burnier, Jérémy Fleury, for Energy efficient windows that transmit telephone signals.

Watt d’Or 2019 “Energy efficient mobility” by Swiss Federal Office of Energy, Andreas Schüler, Olivia Bouvard, Luc Burnier, Jérémy Fleury (as part of a team headed by BLS train company and Basel University), for Nina trains energy efficiency modernisation. Contribution: energy efficient windows transparent to phone signals.

Award winning publications

Jing Gong, André Kostro, Jean-Louis Scartezzini, Andreas Schüler, Feasibility study on a novel daylighting system with embedded micro compound parabolic concentrators (CPCs). Nonimaging Optics: Efficient Design for Illumination and Solar Concentration XV (Vol. 10758, p. 1075807). International Society for Optics and Photonics. Nonimaging optics best paper award – SPIE Optical Engineering & Applications, 2018, 19-20 August 2018, San Diego, CA, USA

Martin Joly, Yan Antonetti, Martin Python, Marina Gonzalez, Thomas Gascou, Jean-Louis Scartezzini, Andreas Schüler, Novel black selective coating for tubular solar absorbers based on a sol-gel method, Solar Energy Journal Best Paper Award 2012-2013

Peter Oelhafen, Andreas Schueler, Nanostructured materials for solar energy conversion, Solar Energy Journal Best Paper in Energy Conversion Award 2005/2006

Publications