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

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Finally, a new in-house built, large area and automated deposition system has been taken into use for
the fabrication of heterojunction solar cells: the usable deposition area is 410 × 520 mm with
RF-frequency of 40 MHz [6]. We managed to obtain outstanding passivation on both n-type and p-type
c-Si wafers in this system. For n-type FZ c-Si, implied Voc as high as 726 mV and �eff as high as 4.7 ms
have been obtained; for p-type c-Si �eff as high as 6.8 ms. Spatial uniformity is excellent for the a-Si:H
films. The excellent passivation results in this large area deposition system are a promising basis for
the fabrication of high efficiency silicon heterojunction solar cells.
Collaborations
Due to the nature of this European Project, IMT is in collaboration with major the European Institutes,
Universities and Companies working on heterojunction devices. These partners include CEA-INES,
CNRS, ALMA and Photowatt from France; ECN and Universiteit Utrecht from the Netherlands; ENEA
from Italy; IMEC from Belgium; and Helmholtz Zentrum Berlin, Q-Cells, and Solon from Germany.
Evaluation 2008 and Outlook 2009
Hetsi was successfully launched in early-2008. From the beginning of the project, we pursued the
amorphous/crystalline silicon interface recombination modeling for fast heterojunction solar cell single
process step analysis and improvement. Critical parameters have been identified for successful device
fabrication. To continue this work, new cleanroom facilities will be taken in use in early 2009, featuring
an industrial compatible wetbench for texturing studies, a new multi-chamber PECVD system for further
device development and layer development. In addition, the focus will be shifted next year to larger
area devices for which different metallization schemes will be tested. In early 2009, a state-of-theart
screen-printer will be installed as well as at IMT.
References
[1] L. Fesquet, S. Olibet, E. Vallat-Sauvain, A. Shah, C. Ballif: High quality surface passivation and heterojunction fabrication
by VHF-PECVD deposition of amorphous silicon on crystalline Si: Theory and experiments, to be published
in the Proceedings of the 22th EU-PVSEC, Milano, Italy, 2007.
[2] S. De Wolf, S. Olibet, and C. Ballif, Stretched-exponential a-Si:H / c-Si interface recombination decay, Appl. Phys.
Lett. 93, 032101 (2008).
[3] S. Olibet. E. Vallat-Sauvain, and C. Ballif, Model for a-Si:H / c-Si interface recombination based on the amphoteric
nature of silicon dangling bonds, Phys. Rev. B, 035326 (2007).
[4] S. De Wolf and M. Kondo, Abruptness of a-Si:H / c-Si interface revealed by carrier lifetime measurements, Appl.
Phys. Lett. 90, 042111 (2007).
[5] S. Olibet, C. Monachon, A. Hessler-Wyser, E. Vallat-Sauvain, L. Fesquet, J. Damon-Lacoste, S. De Wolf, and C. Ballif,
Textured silicon heterojunction solar cells with over 700 mv open-circuit voltage studied by transmission electron
microscopy , , to be published in the Proceedings of the 23th EU-PVSEC, Valencia, Spain, 2008.
[6] J. Damon-Lacoste, L. Fesquet, S. Olibet, and C. Ballif, Ultra-high quality surface passivation of crystalline silicon
wafers in large area parallel plate reactor at 40 MHz, accepted for publication in Thin Solid Films (2008).
HETSI, S. De Wolf, IMT Neuchâtel
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