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Passivation of optically black silicon by atomic layer deposited Al 2O3

: Otto, M.; Kroll, M.; Käsebier, T.; Ziegler, J.; Sprafke, A.N.; Wehrspohn, R.B.

Volltext ()

Energy Procedia 38 (2013), S.862-865
ISSN: 1876-6102
International Conference on Crystalline Silicon Photovoltaics (SiliconPV) <3, 2013, Hameln>
Zeitschriftenaufsatz, Konferenzbeitrag, Elektronische Publikation
Fraunhofer IWM ( IMWS) ()

Optically black silicon nanostructures show excellent anti-reflection and light trapping properties minimizing reflection losses to less than 1.6% between 300-1100 nm. Our light-trapping scheme enables an absorption enhancement factor of 10 at the band edge of silicon (1150 nm) as compared to a simulated perfect ARC, where the Yablonovitch limit corresponds to a factor of 15. Just recently it was shown that similar wet-chemically black etched silicon surfaces can be exploited to fabricate high efficiency solar cells [1]. Towards the integration of our structures into a solar cell device, the passivation performance of atomic layer deposited thin Al2O3 films is investigated on a variety of black etched structures. The coatings lead to measured surface recombination velocities of less than 13 cm/s on bifacially black structured as well as 12 cm/s on polished 1-5 cm p-type Si CZ wafers. Thinner layers promise to be even more effective. This technology will enable high effi ciencies on various solar cell concepts.