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Hydroxyl functionalization improves the surface passivation of nanostructured silicon solar cells degraded by epitaxial regrowth

: Song, J.-W.; Nam, Y.-H.; Park, M.-J.; Shin, S.-M.; Wehrspohn, R.B.; Lee, J.-H.


RSC Advances 5 (2015), Nr.49, S.39177-39181
ISSN: 2046-2069
Fraunhofer IWM ( IMWS) ()

Metal-assisted chemical etching is useful and cost-efficient for nanostructuring the surface of crystalline silicon solar cells. We have found that the nanoscale epitaxy of silicon occurs, upon subsequent annealing, at the Al2O3/Si interface amorphized by metal-assisted etching. Since this epitaxial growth penetrates into the pre-formed Al2O3 film, the bonding nature at the newly formed interfaces (by the regrown epitaxy) is deteriorated, resulting in a poor performance of Al2O3 passivation. Compared to the conventional hydrogen (H-) passivation, hydroxyl functionalization by oxygen plasma treatment was more effective as the wafer became thinner. For ultrathin (50 μm) wafers, 30% depression in surface recombination velocity led to the improvement of 15.6% in the short circuit current. The effectiveness of hydroxyl passivation validated by ultrathin wafers would be beneficial for further reducing the wafer cost of nanostructured silicon solar cells.