Reducing the Angular Colour Dependence of Building Integrated Photovoltaic Modules Based on Optical Interference Coatings

This work focuses on optical interference coatings applied on the back side of the front glass to achieve the colouration of crystalline silicon-based photovoltaic (PV) modules. Such interference coatings can be designed to obtain desired aesthetic properties combined with a relatively low loss in power conversion efficiency, which makes this colouring technology attractive for building integrated photovoltaics. The visual appearance and power conversion efficiency are influenced by the coating design parameters such as the number of layers, design wavelength, layer thicknesses and refractive indices, and the glass surface's texture. One drawback of using optical interference coatings is that the colour changes with the observation angle. In order to reduce the angular colour dependence, we have fabricated and analyzed PV mini-module prototypes with both different glass textures and different coating design parameters. A simulation model was adopted to investigate relevant coating designs and predict their performance, with the aim of achieving low angular colour dependence and high-power conversion efficiency.