All-dielectric Structural Color

Metasurface-based Coatings for Photovoltaic Devices

Anton Ovcharenko1,* and Lieven Penninck2,*

1 Department of Computational Physics, V. N. Karazin Kharkiv National University, 2PlanOpSim NV, 29 Boterbloemstraat, Melle 9090, Belgium
*anton.ovcharenko@karazin.ua, lieven.penninck@planopsim.com

Abstract:

We show that an all-dielectric structural color metasurface can be integrated atop photovoltaic devices to balance vibrant color generation with tolerable solar efficiency loss. Using RCWA simulations, we optimize nanostructure geometry, achieving narrow reflectance peaks. © 2025 The Author(s)

Introduction

Structural color arises from the interaction of light with periodic nanostructures rather than chemical pigments or dyes that rely on selective absorption of light. Light interaction with nanostructures via physical processes such as interference, diffraction, and scattering can give rise to vivid and often angle-dependent colors with very high resolution. This mechanism offers several advantages over conventional pigments, including enhanced durability, resistance to photobleaching, and the potential for dynamic color tuning through external stimuli. The integration of structural color devices with photovoltaic (PV) systems has garnered significant interest due to the potential for combining aesthetic customization with energy harvesting. [1, 2] It opens new possibilities for applications such as building-integrated photovoltaics, where visual appeal is often as important as energy efficiency. In order to maximize the benefits of structural color in PV devices, it is essential to optimize the color quality while minimizing the impact on solar cell performance.

In this study, we explore an all-dielectric structural color solution for this task. By running a series of RCWA
simulations, we generate a set of reflectance and transmittance spectra and search for the best match of ideal reflective color profile.

Methodology

We investigate a setup where a structural color metasurface is placed on top of a polycrystalline silicon [3] solar cell. The metasurface consists of an array of nanoposts made from the same material as the substrate. Additionally, between the two, there is a layer of sapphire (Al2O3), which is used to enhance color quality, as previously reported in Ref. [4]. The structure is embedded in polymethyl methacrylate (PMMA), which acts as an index matching layer to reduce reflection from the substrate. [4] See Fig. 1(a) for the schematic view.

To properly assess the performance of such a setup, we have conducted a comprehensive parameter sweep
study using the PlanOpSim software for numerical electromagnetic simulations. [5] We have varied the nanopostdiameter, height, and spacing, as well as the sapphire thickness. The simulations were performed for a range of wavelengths from 380 nm to 700 nm, corresponding to the visible spectrum. By varying the geometric parameters, a metasurface can be designed to reflect specific wavelengths of light, producing a desired color appearance while allowing the remaining spectrum to pass through to the solar cell. When optimizing for multiple colors simultaneously, so that they could together on a single device, it is important to find a post height and sapphire thickness combination that compromises on the efficiency for all the colors from the fabrication point of view. At the same time, the periods of the nanostructures can vary from one color to another.

Results

Figure 1(b) shows the results of this paper. We have set out to find an optimal parameter combination for the red, green and blue colors, as well as black, which could be used as a background with the best anti-reflective properties. The figure also compares the reflectance spectra to those of a simple silicon-PMMA interface. As ameasure of color quality, we used a mean squared error metric between the simulated spectra and the ideal ones, which, in our case, meant maximum reflectance between 630 and 650 nm for red, 510 and 530 for green, and 460 and 480 for blue, zero everywhere else. The geometric parameters of the optimal structures are shown in Table 1. To get a better sense of the influence of the metasurface on the amount of energy reflected and transmitted, we have calculated the fractions of reflected and transmitted power for each color:

where R0(λ) and T(λ) are the zeroth-order reflectance and total transmission spectra, respectively, and W(λ)
is the ASTM G173-03 solar irradiance spectrum. Computed values are shown in Table 1. One can immediately
notice that with selective reflectance features the overall reflectance drops, however, so does the transmission by
means of increased absorption and off-normal reflection. Further work should be done to explore better designs to mitigate these drawbacks.

Fig. 1. (a) Schematic view of the simulation setup. (b) Reflectance spectra for bare polycrystalline
silicon-PMMA interface, red, green, blue, and black colors. The lines are colored according to the
color they represent.

Table 1. Geometric parameters of the structural color metasurface.

References

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