TOPCon Solar Cells Made of n-Type and p-Type Epitaxially Grown Silicon Wafers

Abstract

In the growing silicon photovoltaic module production, the crystalline silicon (c-Si) wafers represent the most energy-intensive process steps. Epitaxially grown c-Si wafers (EpiWafers) detached from reusable substrates allow a significant reduction of this energy consumption. In this work, we studied the suitability of these EpiWafers with tunnel oxide passivating contact (TOPCon) solar cells—the mainstream technology—with a special focus on high temperature stability in the range of 1000°C, as required for the boron emitter diffusion. Small area TOPCon solar cells made of n-type EpiWafers achieved an efficiency of up to 23.4%, which represents the highest value reported yet for EpiWafers exposed to high temperatures. A detailed electronic quality analysis of n-type and p-type EpiWafers does not indicate a degradation after the high temperature steps. The efficiency potential is demonstrated with TOPCon solar cells fabricated on epitaxially grown reference wafers, which achieved efficiencies of up to 24.4% and 24.7% for n-type and p-type wafer polarity, respectively. These results closely match those of solar cells fabricated in parallel on high-quality FZ wafers, showcasing the excellent material quality and high temperature stability of epitaxially grown wafers. Thus, these results demonstrate the suitability of EpiWafers for high efficiency TOPCon solar cells with low CO₂ footprint.