Antireflection and surface passivation behaviour of SiO2/Si/SiO2 quantum wells on silicon

Quantum wells (QWs) consisting of Si and Si-related materials (such as SiO2) are of interest for solar cell work because they can possibly be used as a surface passivating antireflection (AR) coating or as the top cell in an all-silicon tandem solar cell. In this study, we fabricate SiO2/Si/SiO2 QW layers by RF magnetron sputtering and thermal oxidation. On high-resistivity (300 Ω cm) n-type silicon wafer substrates, the effective surface recombination velocity provided by our SiO2/Si/SiO2 QWs is around 4 cm/s for 13 Å Si thickness and 480 cm/s for 150 Å Si thickness. The parasitic optical absorption in the well-passivating QWs is negligible for terrestrial photovoltaic applications. However, they have very poor AR properties on Si wafers and hence would have to be covered by an additional reflection reducing dielectric film.