The black silicon (b-Si) solar cells suffer from increased surface recombination rates due to the larger surface area resulting in poor spectral response especially at short wavelengths. This effect is often more detrimental for the final device operation than the gain from the reduced reflectance. In addition, b-Si suffers from aging phenomena; the huge internal surface of the needles tends to be progressively oxidized or contaminated by impurities when in contact with air. The low stability of structural and optical properties over time is crucial for solar cells.  The optical properties and performance parameters of b-Si solar cells coated with silicon dioxide (SiO2) thermal films have been investigated.  Figure shows the reflectance of conventional (polished surface) and bi-Si solar cells samples with and without passivation SiO2 films. Table shows the performance parameters (such as open circuit voltage - Voc, short-circuit current - Isc, fill factor - FF, and conversion efficiency - μ) of b-Si solar cells with and without passivation SiO2 film.  The SiO2 film does not only have low surface state density at Si-SiO2 interfaces but also reduces the surface doping concentration via thermal oxidation processing leading to the lower Auger recombination. The combination of b-Si and thermal SiO2 film demonstrates promising results. The thermal oxidation: i) retains low reflectivity of the b-Si surface; ii) does not degrade performance parameters; iii) provides better surface-passivation quality and iv) has a protective function and stabilizes the properties of the b-Si surface at the time.