Surface (Photo)Voltage Monitoring in Roll-to-Roll Deposition of Thin Film Silicon Solar Cells

The Kelvin probe is a non-contact, non-destructive vibrating capacitor device that measures the work function difference between a conducting sample and a vibrating tip. This contribution focuses on inline monitoring of the surface (photo) voltage of deposited silicon layers. We apply a custom-built in-situ Kelvin probe, operated in a roll-to-roll PECVD system, located immediately after the plasma zones to enable direct feedback to the controlling system of the plasma deposition. The surface photovoltage of nip thin film Si solar cells increases with increasing Voc. The results imply that inline, contactless measurements of the open circuit voltage are possible and that thus monitoring the doped layer quality during roll-to-roll production is feasible.