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

Abstract

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.

High Anti-Reflection Large-Scale Cup-Shaped Nano-Pillar Arrays via Thin Film Anodic Aluminum Oxide Replication

“…There are two important aspects regarding the optical performance of a high-quality quantum efficiency optoelectronic device; one is the AR property from a surface, and the other one is the capture ability for the entered light. Both of these two aspects have been extensively studied in the field of nanostructured solar cells, especially for thin film solar cells [ 13 , 52 , 53 , 54 ], and have usually been called the light-trapping properties. In order to study the light trapping performance of the CSNP, a silicon-based thin film solar cell model has been built as shown in Figure 5 a, in which the symmetrical two adjacent triangular lattices serve as the smallest simulation area [ 23 ].…”

Reflection Coefficient Calculation of a Structure Including a Porous Silicon Layer with Transfer Matrix Method and FDTD

“…FDTD method can be used for solving electromagnetic problems involving arbitrary geometries with no approximations other than curved structures modelled with a stair step approximation which cause errors [20,21]. Also, FDTD method needs great computation power and time but it can simulate electromagnetic waves interaction with actual geometries more accurately [8].…”

“…All methods predict the broadband reflection of tapered nanostructures with periods smaller than the wavelengths of light of interest and lengths that are at least a large portion of the wavelengths. In [8], reflection spectra are obtained for designed nanostructure geometries on amorphous silicon thin-film solar cells, using a Ray Tracing modelling approach. This coating reduced reflectance in the wavelength of 300-800 nm range by an average of 2.665% and 11.36% at 0• and 80• incident light, respectively.…”

A New Texturing Approach of a Polyimide Shielding Cover for Enhanced Light Propagation in Photovoltaic Devices

“…These average height values of the granules, calculated from the cross-section profile from Figure 10D,H, are quite small (up to 200 nm), with respect to the wavelength of light (400-700 nm). In this context, mainly the well-dispersed grain-like nanopatterns discovered on CBDA-pBAPS can create a refractive index gradient between air and the adjuvant layer in the PV structure, favoring the reduction in the light reflection [46]. In terms of the fractal complexity of the shape, both parameters derived from the fractal analysis (Table 2) of the small particles.…”