Record low surface recombination velocities on low-resistivity silicon solar cell substrates

In this paper, the lowest ever reported effective surface recombination velocities S_eff on typical p-type low-resistivity silicon solar cell substrates are presented. We obtain this surface passivation by means of remote plasma silicon nitride films fabricated at 375°C. On polished as well as on chemically textured silicon surfaces, the applied low-temperature passivation scheme is significantly superior to high-temperature passivation by state-of-the-art thermal oxides. On polished 1.5-Ωcm p-Si wafers, an extremely low S_eff value of 4 cm/s is obtained. Because of the enormous potential of these plasma silicon nitride films as passivation medium for the rear surface of silicon solar cells, we also investigate silicon nitride-passivated, Al grid-covered p-Si surfaces as used by us in bifacial solar cells. On such samples we measure spatially averaged S_eff values as low as 135 cm/s