Angle-dependent reflectance of isotextured silicon

Multicrystalline silicon (mc-Si) is the workhorse of photovoltaics with a market share above 60%, being acidic textured (isotextured) silicon the standard. For optical simulations, the spherical caps model is widely applied, but it was reported that is does not correctly describe the angular dependence of reflection. In this work, our first objective is to verify this. Secondly, we want to obtain an improved model for optics of isotextured mc-Si wafers and solar cells able to describe the light trapping properties of cells and modules correctly. We investigate the reflectance of isotextured silicon by varying the angle of incidence of the light between 8° and 80°. We perform measurements of nine isotextured samples, obtaining reflectance curves with a similar shape, but they differ by up to 60%abs from previously published data. The first simulations are performed using the spherical caps model, which is shown to be inaccurate to describe the angle-dependent reflectance of isotextured silicon. In the second set of simulations we vary the texture morphology, reducing the deviations of the simulation from the measurement from 8% to 1.2% for incident angles smaller than 60°. We conclude that alternative morphologies are worth doing further research.