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Front Side Optimization on Boron- and Gallium-Doped Cz-Si PERC Solar Cells Exceeding 22% Conversion Efficiency

: Lohmüller, E.; Greulich, J.; Saint-Cast, P.; Lohmüller, S.; Schmidt, S.; Belledin, U.; Fellmeth, T.; Mack, S.; Emanuel, G.; Krieg, K.; Zimmer, M.; Kunert, R.; Zobel, F.; Linse, M.; Horzel, J.; Meßmer, M.; Wolf, A.; Preu, R.


Pearsall, Nicola (ed.):
37th European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC 2020 : 07-11 September 2020, Online Conference
München: WIP, 2020
ISBN: 3-936338-73-6
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <37, 2020, Online>
Conference Paper
Fraunhofer ISE ()
Photovoltaik; boron; Cz-Si; diffusion; front side optimization; gallium; PERC; screen printing; Silicium-Photovoltaik; Charakterisierung von Prozess- und Silicium-Materialien; Dotierung und Diffusion; Oberflächen: Konditionierung; Passivierung; Lichteinfang; Metallisierung und Strukturierung; Pilotherstellung von industrienahen Si-Solarzellen

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.