Structural coloration for photovoltaics via sub-monolayer disordered Mie resonators

Abstract

Building-integrated photovoltaics (BIPV) are currently hindered by the esthetic trade-off between power conversion efficiency and visual appeal. Conventional colorization methods generally fall into two categories: organic absorption-based dyes, which suffer from high parasitic losses and limited durability, and interference-driven multilayer thin films stacks, which exhibit undesirable iridescence. In this work, we demonstrate highly stable, largely angle-independent color PV modules utilizing a disordered sub-monolayer of dielectric silicon nanoparticles (Si NPs). By leveraging localized Mie resonances within high-index Si nanospheres (100–200 nm in diameter), the angle-dependence of the reflected color is strongly reduced. These Si NPs are encapsulated in a protective polymer shell to prevent clustering, thereby maintaining sharp scattering peaks and color saturation. The nanostructures were deposited via slot-die coating, providing a scalable fabrication route for large-area modules (∼50 cm2 PV devices demonstrated here). Numerical simulations support the experimentally observed spectrally selective reflectance driven by such Si NPs photonic glasses. We achieve a relatively broad CIE 1976 color gamut, including saturated blue, green, and yellowish hues, by varying the size and surface density of Si NPs while maintaining less than 10%–20% relative photocurrent PV loss. This offers a versatile design palette for high-efficiency, esthetically pleasing urban BIPV energy harvesting.