Programm Photovoltaik Ausgabe 2009 ... - Bundesamt für Energie BFE

So far, 7% stabilised efficiency a-Si:H cells could be achieved on plastic, which is close to the 7.3%
obtained on glass for the same active layer thickness of 200nm.
Regarding the tandem cells, excellent results could be reached within the last months. The IMT put a
lot of efforts on the development of the intermediate reflector and on the Jsc matching of the top and
bottom cells when intermediate reflector is used; 10.1% stable efficiency could be obtained on glass.
9.8% stabilised efficiency could be achieved on plastic [3, 4] with 2.5�m thick bottom cells, according
to the results obtained on glass.
Table 1: Latest tandem cells with 2.5 �M bottom cells and intermediate reflector. Initial values are
given in brackets.
Voc [mV] FF [%]
Jsc (top)
[mA/cm 2 ]
Jsc (bottom)
[mA/cm 2 ]
Efficiency
[%]
ZnO/text-Ag/glass 1.35 (1.32) 65 (66) 11.7 (12.4) 11.5 (11.9) 10.1 (10.3)
ZnO/Ag/
Plastic PEN
1.29 (1.34 ) 64 (68) 11.9 (12.3) 12.1 (12.3) 9.8 (11.2)
Collaborations
The nature of the project ensured a collaborative and dynamic exchange of expertise, samples and
technological advices among the partners. In the frame of the project, IMT maintained direct contacts
with ECN (cell deposition on textured back reflector), Fraunhofer FEP (roll-to-roll backreflector coating),
University of Ljubjana (optical and electrical simulations), University of Barcelona (direct embossing
of substrates), VHF-Technologies (cell deposition, electrode development) and Rofin (cell structuration).
Conclusion
FLEXCELLENCE can be viewed as a successful collaborative project under IMT’s coordination.
Technological developments (hardware development) took in some cases more time than expected
but the different aspects necessary for the production of high efficiency thin-film modules by roll to roll
could be investigated. Good results were achieved, both on the hardware/equipment side and on the
cell processing side, with sometimes some results at a world-class level. At the end of the project
some of these results were already implemented in production at VHF-technologies, or in some other
cases are ready for commercialization. A production cost assessment has been realized and has
shown that the market requirements are reasonably achievable. The results presented by the IMT at
the 24 th EU PVSEC in Valencia, Spain, were reporting as one of the highlights in the closing session.
A more detailed presentation of the project results, including from the different partner’s contribution
can be found on the website www.unine.ch/flex.
References
[1] F.-J. Haug, T. Söderström, O. Cubero, V. Terrazzoni-Daudrix, C. Ballif, Plasmonic absorption in textured silver back
reflectors of thin film solar cells, Journal of Applied Physics, Vol 104, pp. -064509, September, 2008
[2] T. Söderström, F.-J. Haug, V. Terrazzoni-Daudrix, and C. Ballif, Optimization of amorphous silicon thin film solar cells
for flexible photovoltaics, Journal of Applied Physics , Vol 103 , pp. 114509-, 2008
[3] F.-J. Haug, V. Terrazzoni-Daudrix, T. Söderström, X. Niquille, and C. Ballif, Development of micromorph tandem solar
cells on flexible low cost plastic substrates, Presented at the 17th International Photovoltaic Solar Energy Conference,
Fukuoka, Japan (2007), 2007
[4] T. Söderström, F.-J. Haug, V. Terrazzoni-Daudrix, X. Niquille, M. Python and C. Ballif, N/I buffer layer for substrate
microcrystalline thin film silicon solar cell, JOURNAL OF APPLIED PHYSICS, Vol 104, pp. -104505, 2008
Flexcellence, V. Terrazoni, IMT Neuchâtel
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