Light scattering from black silicon surfaces and its benefits for encapsulated solar cells

Black silicon (b-Si) has been widely investigated as a potential replacement for more traditional antireflective schemes for silicon solar cells, such as random pyramids, due to its reduced broadband reflectance and improved light-trapping properties. Wavelength and angle resolved scattering (WARS) reflectance measurements provide the means of analysing the amount of light scattered from a textured surface, which can be of interest when considering the amount of light trapped through total internal reflectance (TIR) at various interfaces in an encapsulated photovoltaic module. Here we present and analyse results from WARS measurements on b-Si surfaces fabricated using metal assisted chemical etching (MACE). Large angle scattering is observed for the entire spectrum, increasingly so for shorter incident wavelengths and increasing height of texture features. This is predicted to result in 35–40% of the reflected light being trapped by TIR at the glass-air interface and redirected back onto the sample, when the sample is encapsulated in standard PV module materials. This leads to a calculated additional boost of up to 0.45% in the photogenerated current of an encapsulated black silicon solar cell. This exceeds the calculated 0.21% boost due to TIR predicted for an encapsulated solar cell employing the industry-standard random pyramid texture with a thin film antireflective coating.