Presentation Details
| Microscopic Insights into the Mechanism of LECO-Enabled Fire-through Cu Contact Formation on n-TOPCon (yes) Sagnik Dasgupta1, Ruohan Zhong1, Harvey Gutthrey2, Mengkun Tian1, Vijaykumar Upadhyaya1, Venkata S.A.Mulkaluri1, Donald Intal3, Wook-Jin Choi1, Young-Woo Ok1, Pauls Stradins2, Abasifreke Ebong3, Ruvini Dharmadasa4, Thad Druffel4, Ajeet Rohatgi1. 1Georgia Institute of Technology, Atlanta, GA, USA.2National Laboratory of the Rockies, Golden, CO, USA.3University of North Carolina, Charlotte, NC, USA.4Bert Thin Films, Louisville, KY, USA |
Abstract
Copper is an attractive replacement for screen-printed Ag in industrial n-TOPCon, but its high diffusivity makes Cu-contacting a passivation/stability problem. Here, we link LECO-driven electrical improvements in rear fire-through Cu contacts to changes in Cu/n-TOPCon interfacial microstructure. Cells with rear Cu fired at 530 °C, transition from non-ohmic to low-resistance behavior after LECO, with contact resistivity reduced to 19.7 mΩ.cm2 and a champion efficiency of 24.3% (VOC = 732 mV). Cross-sectional STEM-HAADF/EDXS reveals faceted crystalline Cu-rich particles embedded in n-poly-Si, with higher density after LECO; plan-view SEM/EDXS shows denser crystallite clusters and a ~2.67× increase in background-subtracted Cu peak area. Lastly, we used STEM nanodiffraction to recognize that the formed crystallites are likely a compound copper silicide which mitigates copper diffusion. These observations are consistent with localized Joule heating during LECO that expands firing-formed contacted regions and promotes crystallite growth, enabling Ag-competitive performance without the passivation loss associated with higher firing temperatures.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.