Plating on TOPCon as a Way to Reduce the Fabrication Costs of i-TOPCon Solar Cells
i-TOPCon solar cells commonly make use of a TOPCon/SiNx stack at the rear side. For screen-printed contacts, a certain TOPCon layer thickness in the range of 110 to 150 nm is usually required to prevent spiking of the contacts. In this publication, it is shown that laser contact opening can be used in a thickness range of 60 to 90 nm with a J0,met of around 50 fA/cm2 for a thickness of 90 nm. The J0,met of over 1000 fA/cm2 for the screen-printed references indicates that in this thickness range screen-printing is not a viable technology with state-of-the-art pastes. However, the reduction in the TOPCon thickness can give a significant advantage in the cost of ownership for the TOPCon deposition due to the reduced deposition time. The variation of the TOPCon thickness is investigated on solar cells as well proving again that screen-printing on less than 100 nm thick TOPCon layers should be avoided. On the other hand, laser contact opening in combination with plated contacts is shown to work well reaching an efficiency of 22 % limited by the front side emitter passivation and contact.