We propose a two-layer anti-reflective coating (ARC) that will have omni-directional properties. This coating will guide the light that is incident from oblique angles and orient it to become perpendicular to the solar cell surface. The top-most part of the coating will have a graded index of refraction, starting from an index of 1 at the air interface and gradually increasing to an index of about 1.5 at the interface between the two coating layers. This top layer will be made out of cheap polymer that can be deposited by dip-coating, and the graded index will be achieved by texturing the polymer to have up-right pyramids. As the light travels through this layer, it will bend to become perpendicular to the surface of constant index regardless of initial angle of incidence. The bottom layer of our proposed coating will consist of a standard silicon nitride (SiN) thin film layer that will act as an interference ARC between the polymer and the silicon surface of the solar cell to minimize reflections between each layer. We believe this approach offers cost and weight advantages over not only current mechanical solar directing systems, but also other similar graded ARCs based on silicon oxide.
Keywords: Anti-Reflective Coating, Anti-Reflective Coating, Tracking, Photovoltaic
