Thermal oxidation as a key technology for high efficiency screen printed industrial silicon solar cells

In this paper various options to integrate thermal oxidation into industrial cell production are presented, maintaining large parts of the standard cell fabrication process. Both the use of thin (15 nm) and thick (200 nm) wet thermally grown oxides are successfully implemented into pilot production at the Fraunhofer production research platform PV-TEC [1]. Solar cells are fabricated with both type of processes. On large area (149mm²) Cz-Si substrates 18% efficiency have been achieved. Furthermore a cost calculation including process and equipment improvements is carried out for the thermal oxidation process and it is shown that the cost for such a process can be well below 10€ct per wafer for thick and below 5 €ct per wafer for a thin oxide, thus meeting industrial requirements for cost effective production.