Multilayer thin film design for neutral-colored opaque photovoltaics

Considering the less appealing aesthetics of traditional photovoltaics (PV) panels, the colorization process is a crucial step towards their broader application in building-integrated photovoltaics (BIPV) systems, thus facilitating carbon peak and neutrality. For achieving colored PVs in a full-color gamut including neutral colors like grey and white, this research proposes a design method for multilayer dielectric thin films based on a pre-configured structure. The optimized design ensures that most reflected light is concentrated on the regions easily perceptible to human eyes, enabling colored PVs to achieve high power conversion efficiency (PCE) and perceptual lightness (L⁎) simultaneously. With a color difference to the objective color coordinates smaller than 3, the designed colored PVs corresponding to RAL 9006, RAL 7035, and RAL 9003 can achieve 89.20 %, 78.69 %, and 64.78 % of the power generation compared to the reference module. The PCEs of the neutral-colored PVs are even higher than those in the normal case where a constant reflectivity in the VIS region is set. For further improvements, the maximum color difference derived from thickness errors is reduced from 33.01 to 8.57 with the absolute PCE sacrifice of 1.56 %. The mitigation of angular dependence also leads to a 2.46 % drop in PCE when the maximum color difference caused by tilted incidence is only 4.07. The proposed optimization method provides a theoretical guide for designing multilayer thin film filters applied on high-efficiency colored PVs, which will contribute to the future advancement of BIPV technology.