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Front Side Optimization on Boron- and Gallium-Doped Cz-Si PERC Solar Cells Exceeding 22% Conversion Efficiency
E. Lohmüller, J. Greulich, P. Saint-Cast, S. Lohmüller, S. Schmidt, U. Belledin, T. Fellmeth, S. Mack, G. Emanuel, K. Krieg, M. Zimmer, R. Kunert, F. Zobel, M. Linse, J. Horzel, M. Meßmer, A. Wolf, R. Preu
Diffusion, Screen Printing, Optimization, PERC, Cz-Si, Front-Side
Silicon Materials and Cells
Subtopic: High Temperature Route for Si Cells
Event: 37th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2DV.3.19
516 - 520
ISBN: 3-936338-73-6
Paper DOI: 10.4229/EUPVSEC20202020-2DV.3.19
0,00 EUR
Document(s): paper


This work reviews on our industrial-oriented passivated emitter and rear cell (PERC) baseline process for Czochralski-grown silicon (Cz-Si) wafers at the Fraunhofer ISE PV-TEC pilot-line. We perform several front side optimizations based on homogeneous emitter doping: finger width reduction of the screen-printed silver fingers, improved silver paste, and implementation of low-temperature thermal oxidation. This yields peak energy conversion efficiencies of 22.1% for boron-doped Cz-Si from LONGi and 22.2% for gallium-doped Cz-Si from Fraunhofer CSP. We show that gallium-doped Cz-Si wafers offer an industrially feasible option to further improve PERC-type but also other solar cell concepts on p-type Cz-Si. We also demonstrate the possibility to omit regeneration procedures that are needed to suppress the boron-oxygen-related light-induced degradation effects as known for conventional borondoped Cz-Si.