EU PVSEC Programme Online
EU PVSEC 2021, 6 - 10 September 2021
Presentation: 2EO.3.2 Efficiency Potential Analysis of p- and n-Type Epitaxially Grown Si Wafers
Type: Oral
Date: Friday, 10th September 2021
08:30 - 10:00
Author(s): C. Rittmann, J. Dalke, M. Drießen, C. Weiss, F. Schindler, R. Sorgenfrei, M.C. Schubert, S. Janz
Presenter / Speaker: C. Rittmann, Fraunhofer ISE, Freiburg, Germany
Event: Conference Conference
Session: 2EO.3 Feedstock and Wafer Processing / Thin-Film and Foil-Based Silicon Cells
Topic: 2. 1 Feedstock, Crystallisation, Wafering, Defect Engineering
Keywords: Epitaxy, Porous Silicon, Photoluminescence Imaging, Potential, Efficiency Potential
Summary / Abstract: In this paper, we investigate the quality of epitaxially grown, 110 μm thick, n- and p-type silicon (Si) layers deposited in a CVD batch reactor of microelectronic standard. Two types of wafers are characterized: ‘EpiRef’ grown on chemically and mechanically polished reference substrates and ‘EpiWafer’ grown on substrates with a porous silicon detachment layer. EpiRef wafers exhibit excellent minority carrier lifetimes of 2.5 ms for n-type and 1.3 ms for p-type. EpiWafers show reduced, but still promising lifetimes of 0.5 ms (in local areas up to 1 ms) for n-type and 40 μs for p-type. For EpiWafers, we found that quality limitations are due to stacking faults as well as interstitial iron contamination for p-type. An efficiency limiting bulk recombination analysis (ELBA), allows for an assessment of the corresponding efficiency potential assuming a TOPCon cell model with a cell limit of 25.9 % for n-type and a TOPCoRE cell model with a cell limit of 26.5 % for p-type. In selected 1 cm² areas, potential efficiencies of EpiRef wafers are only -0.4 %abs below the theoretical cell limit for n-type and -1.3 %abs for p-type whereas EpiWafers feature losses of -1.2 %abs for n-type and even -5.4 %abs for p-type.