Surface passivation of silicon solar cells using plasma-enhanced chemical-vapour-deposited SiN films and thin thermal SiO2/plasma SiN stacks

Two different techniques for the electronic surface passivation of silicon solar cells, the plasma-enhanced chemical vapour deposition of silicon nitr ide (SiN) and the fabrication of thin thermal silicon oxide/plasma SiN stac k structures, are investigated. It is demonstrated that, despite their low thermal budget, both techniques are capable of giving an outstanding surfac e passivation quality on the low-resistivity (similar to1 Ohm cm) p-Si base as well as on n(+)-diffused solar cell emitters with the oxide/nitride sta cks showing a much better thermal stability. Both techniques are then appli ed to fabricate front- and rear-passivated silicon solar cells. Open-circui t voltages in the vicinity of 670 mV are obtained with both passivation tec hniques on float-zone single-crystalline silicon wafers, demonstrating the outstanding surface passivation quality of the applied passivation schemes on real devices. All-SiN passivated multicrystalline silicon solar cells ac hieve an open-circuit voltage of 655 mV, which is amongst the highest open- circuit voltages attained on this kind of substrate material. The high open -circuit voltage of the multicrystalline silicon solar cells results not on ly from the excellent degree of surface passivation but also from the abili ty of the cell fabrication to maintain a relatively high bulk lifetime (>20 mus) due to the low thermal budget of the surface passivation process.