Modelling technique and analysis of porous anti-reflective coatings for reducing wide angle reflectance of thin-film solar cells

Bio-inspired anti-reflective (AR) coatings with porous graded refractive index structures are known to considerably reduce the reflectance of light at optical interfaces, however, research is lacking for thin-film cell application. Ray Tracing software coupled with the Effective Medium Theory were used to simulate the reflectance of nanostructured coatings placed above a thin-film system. The most optimal coating was paraboloid-shaped, with 300 nm nipple heights and spacings of 15%. The non-zero refractive index 'step' aids light trapping and energy absorption. This coating reduced reflectance in the λ = 300–800 nm range by an average of 2.665% and 11.36% at 0∘ and 80∘ incident light, respectively, whilst increasing annual energy output by 4.39% and 5.39% for standard UK roof and vertical window tilts, respectively. Significant wide angle reflectance capabilities are demonstrated at specifically λ = 300 nm and 80∘ incident light, with a reflectance reduction of 19.192%. There are now many promising manufacturing techniques for these porous nanostructures, such as AR or wavelength filtering coatings for photovoltaics. Further understanding of the exact parameters needed to replicate these nanostructures must be explored to proceed.