Bulk passivation in silicon ribbons: a lifetime study for an enhanced high efficiency process

The effectiveness of hydrogenation either by deposition plus firing of a PECVD SiN layer in a conventional belt furnace or by remote H-plasma was compared quantitatively using spatially resolved lifetime measurements for EFG and string ribbon. Additionally the effect of a preceding phosphorous gettering on the hydrogenation and the presence of a screen printed rear side aluminum during firing was analyzed. Wafer areas with the presence of a rear side aluminum show additional lifetime improvements for both hydrogenation methods probably due to a gettering effect. With preceding P-gettering hydrogenation by SiN deposition plus firing is superior to remote H-plasma. A synergetic effect of a rear side aluminum as described elsewhere is not obtained. First high efficiency EFG solar cells using a PECVD SiN fired in a conventional belt furnace were processed with efficiencies in the 17-18% range.