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Plasma etched PERC and buried base contact solar cells

: Schaefer, S.; Preu, R.; Lüdemann, R.; Glunz, S.W.

Scheer, H. ; European Commission:
Sixteenth European Photovoltaic Solar Energy Conference 2000 : Proceedings of the international conference held in Glasgow, United Kingdom, 1 - 5 May 2000
London: James & James, 2000
ISBN: 1-902916-18-2
European Photovoltaic Solar Energy Conference <16, 2000, Glasgow>
Conference Paper
Fraunhofer ISE ()

Two types of solar cells are presented that are based to a significant extent on plasma processes. The first type is the passivated emitter and rear cell (PERC) with silicon nitride passivation of the rear side. SiNx is known to provide excellent surface recombination velocities of about 5 cm/s. However, SiNx is barely etchable wet chemically, therefore we have developed damage-free plasma etch processes in order to open the contact holes in the SiNx. These SiNx passivated and plasma etched PERC cells achieve maximum open-circuit voltages of 655 mV and maximum efficiencies of 20.3%. The second cell type leads to the buried base rear contact cell. It is single-side contacted with self-aligned base metallisation in plasma etched grooves. Due to deliberate under-etching of the mask metal is only deposited on the base of the groove in the succeeding evaporation step. Redundant metal is removed by lift-off, no additional metal etch step for contact separation is necessary. Thus, only one mask is needed for the base area and the metal contact definition. An efficiency of 16.3% has been obtained so far.