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  • People involved :
    • Permanent Researchers : Julien Cardin, Christian Dufour, Fabrice Gourbilleau, Christophe Labbé
    • Young Researchers : Yong-Tao An (PhD), Olivier Debieu (Post-Doc), Kalpana Rani Dey (Post-Doc), Nicolas Guth (Post-doc), Pratibha R. Nalini (PhD).
  • Projects :
    • DGA-REI (2009-2011),
    • DSM/ENERGIE - HOFELI (2011-2012),
    • Interreg IVB-ENERMAT (2010-2012),
    • Interreg IVA – MEET (2012-2015),
    • Projet Emergent Région SOLAIRE (2012-2014),
    • ANR Blanc GENESE (2014-2017),
    • PHC ORCHID (2015-2016).

The expertise acquired in the rare earth-doped Si-based thin films for photonic applications has naturally led to the emergence of a new thematic dealing with the better management of the incident light in the solar cells. One of the possible ways could be the use of quantum confinement properties of Si nanocrystals to promote efficient absorption of photons in the visible range of the solar spectrum. Another way to improve the efficiency of solar cells is to develop frequency conversion layers for transforming an energetic photon in two infrared photons that will be absorbed and converted by the Si solar cell. Unlike systems proposed so far in the literature that are related to glasses doped with lanthanide ions, the objective of our research is to provide a system compatible and directly applicable to the PV industry.

The most significant results were obtained on the couple ion Tb:Yb incorporated into an oxynitride matrix to approach the anti-reflective layer of silicon nitride used in PV modules based on silicon. The fine optical measurements have shown the potentiality of the sensitizing SixOyNz matrix that is able to absorb over a wide range of wavelength (250nm< λ <450nm) before transferring its energy to the surrounding Tb3+ ions.
By incorporating Yb3+ ions in the films, an internal quantum efficiency of 190% was demonstrated. An estimation of the effective gain of such a layer on a silicon solar cell was carried out taking into account the different indices and transfer efficiencies, excitement ... An additional efficiency of 2% has been obtained.
These promising results are at the origin of the ANR project GENESE started in January 2014.
It aims at improving the efficiency of solar cells via a better light management involving several innovative approaches such as frequency conversion layer compatible with the Si PV technology, plasmonic-scattering effect, nanostructuration.
In this framework, we developed recently an all in-situ approach to grow metallic nanoparticles whose size, density, and location can be monitored within the layer. This opens the way to several potential applications.