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High-Efficiency Back-Contact Back-Junction Silicon Solar Cell Research at Fraunhofer ISE
F. Granek, M. Hermle, C. Reichel, O. Schultz-Wittmann, S.W. Glunz
Back Contact, c-Si, n-Type, High Efficiency
Wafer-Based Silicon Solar Cells and Materials Technology
Subtopic: Mono- and Multicrystalline Silicon Cells and Materials, Processing Technology of
Event: 23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain
Session: 2AO.1.2
991 - 995
ISBN: 3-936338-24-8
Paper DOI: 10.4229/23rdEUPVSEC2008-2AO.1.2
0,00 EUR
Document(s): paper


In this paper we present the Fraunhofer ISE approach to high-efficiency back-contact back-junction (BC-BJ) solar cell design and processing. An industrially feasible processing sequence for manufacturing of the BC-BJ solar cells was developed. The best efficiency of 21.3 % was achieved on 1 Ω cm n-type FZ Si. The cell features a phosphorus-doped front-surface field. Local recombination losses called electrical shading were indentified as one of the main cell loss mechanism. In the case of base resistivity of 1 Ω cm the increased recombination over the BSF and undiffused gap areas is responsible for 3.3 % reduction of IQE. This causes around 0.7 % absolute efficiency loss. A novel cell structure with locally overcompensated boron emitters is proposed as a solution to reducing the carrier recombination over the base areas.