An efficient way to substantially increase the surface area coverage of photovoltaic (PV) modules, while maintaining the existent electricity infrastructure, is to integrate such modules into the roofs and facades of buildings. Aside from the practical technical requirements, such as high power conversion efficiency (PCE), low cost, and long lifetime, photovoltaic modules for building applications also necessitate an aesthetically attractive design, which can be achieved by finetuning their color according to the specific architectural needs of the building [1,2].

For some PV technologies, intrinsic coloration with a limited selection of colors can be attained by selecting absorbing materials with specific spectral absorption behavior [3,4]. To achieve a broader range of colors typically requires the addition of colored encapsulants, printed glass covers or interlayers in front of the PV module. Most commonly, pigments or chemical colorants are employed to accomplish such coloration, but they tend to absorb a significant portion of the solar spectrum, drastically reducing the PCE of the resulting PV module. A promising alternative to overcome such issues is to take advantage of the interference effects between non-absorbing dielectric materials with contrasting refractive indexes to design PV modules with vivid structural colors and low optical losses [5,6].

Periodic distributed Bragg reflectors (DBRs) have been considered in some previous works to realize structural coloration in PV modules [7,8], but they typically fail to reproduce some colors, especially reds, owing to the appearance of higher-order interference peaks in the reflectance spectra. To reach a broader color gamut thus requires breaking up the periodicity inherent to DBRs in a controlled way, such that the optical response of the PV module is tuned to achieve the desired coloration. In the present work, a numerical approach combining the electromagnetic description of light propagation together with the use of optimization algorithms is considered to optimize the configuration of a dielectric multilayer structure deposited directly on top of a polymer foil interlayer that is placed in between the substrate and the PV cell, targeting different structural colors for the PV module. As it will be demonstrated, the non-trivial aperiodic structures obtained from this method cover a broader color gamut than the simpler DBRs, and are key to achieve different red hues, including the ones of commonly used raw construction materials, such as clay or brick. As a proof-of-concept, a mini-module with a selected color is assembled by depositing an aperiodic multilayer structure with a numerically optimized configuration on top of a polymeric foil, using a roll-to-roll physical vapor deposition method. This allows not only to validate the numerical predictions regarding the structural color achieved, but also to demonstrate the low photovoltaic loss associated with this sort of multilayers and the scalability of the processes used to fabricate such colored modules.