Title:	EL and LBIC Characterization of Cut Edge Recombination in IBC Solar Cells
Author(s):	M. Bokalič, M. Kikelj, K. Brecl, M. Jankovec, F. Buchholz, V. Mihailetchi, M. Topic
Keywords:	Electroluminescence, LBIC, Edge Recombination, IBC, Silicon (Si) Solar Cells
Topic:	Silicon Materials and Cells
Subtopic:	Characterisation & Simulation of Si Cells
Event:	37th European Photovoltaic Solar Energy Conference and Exhibition
Session:	2CV.1.9
Pages:	308 - 311
ISBN:	3-936338-73-6
Paper DOI:	10.4229/EUPVSEC20202020-2CV.1.9
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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The interconnection of cut cells is a way to improve cell to module efficiency ratio. While this approach minimizes series resistance losses and improves module area utilization, it introduces recombination losses due to imperfect cuts. We propose two additional methods to characterize edge recombination based on multi-wavelength light beam induced current (LBIC) measurements and current-dependent spatially resolved electroluminescence (EL). We test the methods on interdigitated back contact silicon solar cells, which were cut in our laboratory using a not yet optimized procedure with laser ablation and mechanical cleaving. The proposed LBIC based measurement offers an easy interpretation as its result can be directly linked to the local external quantum efficiency, while the proposed EL method can be used as an alternative to the established PL methods without the need of a light source. The results show a clear distinction between cut and uncut edges, which was observed with both methods. The influence of edge recombination is still evident 2 mm away from the cell edge in the EL measurements, and 1 mm and 0.5 mm in the LBIC measurements at 1060 and 642 nm, respectively. For the uncut edge the influence is smaller. Based on the LBIC measurements, the EQE loss at the cut edge is estimated to be 9% for a 1 mm and 0.5 mm wide area along the edge for 1060 and 642 nm, respectively. We also observed a non-intuitive EL behaviour, since the EL signal obtained with high current bias decreases faster towards the edge than the EL signal obtained with low bias current. Similarly, a difference between normalized LBIC profiles is observed at different wavelengths. For the uncut edge, the LBIC signal has a slightly steeper response at 1060 nm than at 642 nm.