Programm Photovoltaik Ausgabe 2008 ... - Bundesamt für Energie BFE

Département fédéral de l’environnement,
des transports, de l’énergie et de la communication DETEC
Office fédéral de l’énergie OFEN
FLEXIBLE PHOTOVOLTAICS: NEXT
GENERATION HIGH EFFICIENCY AND
LOW COST THIN FILM SILICON MODULES
Annual Report 2007
Author and Co-Authors F.J. Haug, C. Ballif
Institution / Company Institute of Microtechnology / University of Neuchâtel
Address Rue A.L. Breguet 2, 2000 Neuchâtel
Telephone, E-mail, Homepage +41 32 718 33 30, +41 32 718 32 01
franz-josef.haug@unine.ch, www.unine.ch/pv
Project- / Contract Number CTI 8809
Duration of the Project (from – to) 01.10.2007 – 30.09.2009
Date 10.12.07
ABSTRACT
The company VHF-Technologies is currently commercialising its “first” generation product, based on
the fabrication of amorphous silicon single junction modules prepared on flat plastic foils. Typical
stabilised module efficiencies are in the range of 4.5%. The IMT of Neuchâtel has achieved in other
projects the fabrication of significantly higher efficiency devices on textured substrates. The objective
of this new CTI project, which started recently, is an improvement or development of specific devices
in the laboratory, and their successful transfer to production processes, aiming at the development of
flexible photovoltaic modules with higher efficiency (gain up to 30-40% relative efficiency). More specifically,
we propose the introduction of a new back reflector structure incorporating diffusely scattering
surfaces which enhance the light path inside the thin silicon layers, assisted by a dielectric mirror
which boosts the reflective properties. In parallel, area losses of the module interconnection will be
substantially reduced by the development of a tandem structure based on amorphous silicon (a-Si).
The final goal of the project is to demonstrate a process suitable for the fabrication of 6% reliable
flexible modules.
Here, we briefly present the first project results. In particular we show that it is possible to fabricate
tandem a-Si/a-Si devices with current up to to 7.4 mA/cm 2 on plastic substrates. An initial efficiency of
8.8% is achieved for such solar cells.
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