Modeling of thin-film interference filters on structured substrates: microfacet-based BSDF versus ray tracing.

We compare two model approaches for the ray optical description of PV modules with coloring based on an interference layer system on the inside of the cover glass. The light scattering is described by a microfacet-based bidirectional scattering distribution function (BSDF) model on the one hand and ray tracing on the other hand. We show that the microfacet-based BSDF model is largely sufficient for the structures used in the context of the MorphoColor application. A structure inversion shows a significant influence only for extreme angles and very steep structures showing correlated heights and surface normal orientations. Regarding an angle-independent color appearance, the model-based comparison of possible module configurations shows a clear advantage of a structured layer system compared to planar interference layers in combination with a scattering structure on the front side of the glass.