Insights into cut-edges of SHJ solar cells by EL and LBIC characterization

Bokalič, Matevž (author), Kikelj, Miha (author), Lipovšek, Benjamin (author), Harrison, Samuel (author), Topič, Marko (author)

Further improvement of shingled cut-cell PV modules requires precise characterization of cut cell edges in order to evaluate, understand and improve cutting process and subsequent re-passivation quality. We use light beam induced current (LBIC) and electroluminescence (EL) measurements to characterize different wafer-based solar cell cutting techniques applied to bifacial silicon heterojunction (SHJ) solar cells: laser ablation and cleaving from the front (L&Cf) and the back (L&Cb) side, thermal laser separation (TLS), and cleaving only. We characterize cut edges from both, the front and the back side of the cell and compare them to the natural (uncut) edge. We present the results in terms of normalized response profiles over different edge types and correlate LBIC and EL profile steepness with edge-zone recombination rate. Measured LBIC profiles are much steeper than EL profiles due to forced charge carrier extraction and lower carrier concentration. By decreasing current injection, EL profiles become steeper and approach LBIC profiles in the limit case. LBIC profiles are also steeper when illuminated from the back, because the minority charge carriers are thereby mostly generated near the main junction and immediately extracted from the bulk. Front and back EL profiles do not show this distinction, because here, in both cases, there are much more charge carriers present in the bulk and radiative recombinations are distributed more homogeneously across the whole depth of the bulk. Due to higher carrier concentration, EL is better correlated with normal operation conditions than LBIC. TLS, cleave only and L&Cf provide overall the steepest profiles, but since TLS and cleave only offers better re- passivation potential, they are the preferred options. L&Cb shows the worst result as laser ablation introduces recombination centres very close to and also in the main junction region. Cleaved only separation provides the best results observed by EL, however 45° rotated ingot is required for this technique. The natural edge profiles exhibit the least steep profiles measured with front and back LBIC, however this is not due to recombination processes but rather due to TCO masking near the edge.

• Language: English
• Keywords: electroluminescence, EL, light beam induced current, LBIC, silicon heterojunction, SHJ, silicon solar cells, edge recombination
• Typology: 1.08 - Published Scientific Conference Contribution
• Organization: FE - Faculty of Electrical Engineering
• Publication status: Published
• Publication version: Author Accepted Manuscript
• Year: 2022
• Number of pages: Str. 63-66
• PID: 20.500.12556/RUL-144025
• UDC: 621.383.51
• DOI: 10.4229/WCPEC-82022-1BO.4.6
• COBISS.SI-ID: 135870467
• Publication date in RUL: 26.01.2023

Record is a part of a monograph

• Title: 8th World Conference on Photovoltaic Energy Conversion : proceedings of the international conference
• Editors: A. Scognamiglio
• Place of publishing: München
• Publisher: WIP
• ISBN: 3-936338-86-8
• COBISS.SI-ID: 135828995

Secondary language

• Language: Slovenian
• Keywords: elektroluminiscenca, LBIC, heterospojne sončne celice, sončne celice, rekombinacije na robu

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P2-0415
• Name: Fotovoltaika in elektronika

• Funder: EC - European Commission
• Funding programme: H2020
• Project number: 857793
• Name: High-performance low-cost modules with excellent environmental profiles for a competitive EU PV manufacturing industry
• Acronym: HighLite