Title:	Solar Cells and Mini-Modules Based on 40 Μμm-Thick Epitaxial Si Foils: Towards Conductive Bonding onto Low-Cost Si Powder Sintered Conductive Carriers from the Recycling of Silicon Waste
Author(s):	H. Sivaramakrishnan Radhakrishnan, K. Van Nieuwenhuysen, J. Govaerts, V. Depauw, T. Bearda, M. Debucquoy, R. Roozeman, J. Heikkinen, M. Schumann, R. Buchwald, H.J. Möller, A. Ciftja, G. Stokkan, E.-J. Øvrelid, A. Stonkus, P. Dubravskij, J. Ulbikas, I. Gordon, J. Szlufcik, J. Poortmans, A. Ulyashin
Topic:	Thin Film Solar Cells and Modules
Subtopic:	Silicon-based Thin Film Solar Cells and Modules
Event:	32nd European Photovoltaic Solar Energy Conference and Exhibition
Session:	3DV.1.15
Pages:	1268 - 1271
ISBN:	3-936338-41-8
Paper DOI:	10.4229/EUPVSEC20162016-3DV.1.15
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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Epitaxial silicon foils (<50 um) lifted-off using the porous silicon-based layer transfer process are used to fabricate heterojunction (HJ) solar cells. Mini-modules with efficiencies above 15% have been fabricated using standard lamination and encapsulation techniques, which have been applied to freestanding epi-Si based HJ solar cells. Analysis of this module highlights the need for bonding these cells onto supporting substrates before module fabrication. We suggest using very low-cost conductive Si carriers as the supporting substrates. Sintering of low-cost Si powder-based ingots, assisted by in-situ doping, has been done by hot pressing or casting of ingots using different types of Si powders and was followed by multi-wire sawing to fabricate thin (~170 μm) supporting highly conductive substrates. The Si material used for these substrates can, in principle, be obtained from Si waste streams, e.g. broken wafers or end-of-line cells in production lines, Si kerf or end-of-life PV modules, making this even more attractive proposition. One important aspect is the development of conductive bonding of epitaxial foils onto low-cost sintered silicon substrates.We evaluated different types of conductive bonding agents. Good mechanical stability was achieved for the bonding processes. These efforts represent the first step towards the wafer-equivalent approach of high efficiency solar cells on thin Si (<50 μm) conductively bonded to low-cost Si substrates. This approach is considered as a promising route for the low-cost Si based PV and a solution module integration of thin Si. This work is done in framework of H2020 EU project CABRISS.