Tailoring Disorder and Quality of Photonic Glass Templates for Structural Coloration by Particle Charge Interactions

Multi-scale structural characterization of ceramic-based photonic glasses for structural colors

Structural colors arise from selective light interaction with (nano)structures, which give them advantages over pigmented colors such as resistance to fading and possibility to be fabricated out of traditional low-cost and non-toxic materials. Since the color arises from the photonic (nano)structures, different structural features can impact their photonic response and thus, their color. Therefore, the detailed characterization of their structural features is crucial for further improvement of structural colors. In this work, we present a detailed multi-scale structural characterization of ceramic-based photonic glasses by using a combination of high-resolution ptychographic X-ray computed tomography and small angle X-ray scattering. Our results uncover the structure-processing-properties' relationships of such nanoparticles-based photonic glasses and point out to the need of a review of the structural features used in simulation models concomitantly with the need for further investigations by experimentalists, where we point out exactly which structural features need to be improved.

Achieving High-Temperature Stable Structural Color through Nanostructuring in Polymer-Derived Ceramics

Structural colors offer a myriad of advantages over conventional pigment-based colors, which often rely on toxic chemical substances that are prone to UV degradation. To take advantage of these benefits in demanding environments, there is growing interest in producing structural colors from ceramics. Polymer-derived ceramics (PDCs) emerge as a compelling choice, presenting two distinct advantages: their enhanced shape ability in their polymeric state associated with impressive temperature resistance once converted to ceramics. This study pioneers the fabrication of noniridescent structural colors from silicon oxycarbide (SiOC) PDC, enabled by the nanostructuring of an inverse photonic glass within the PDC material. This design, a functionally graded material with an inverse photonic glass (FGM-PhG) structure, leverages the innate light-absorbing properties of SiOC, yielding a vivid structural color that maintains its saturation even in white surroundings. This study elucidates the process-structure-properties relationship for the obtained structural colors by investigating each layer of the functionally graded material (FGM) in a stepwise coating deposition process. To further emphasize the exceptional processing flexibility of PDCs, the three-step process is later transferred to an additive manufacturing approach. Finally, the FGM-PhG structural colors are demonstrated to have remarkable thermal stability up to 1000 °C for 100 h, possibly making them the most thermally stable ceramic structural colors to date.

Tuning disorder in structurally colored bioinspired photonic glasses

Colloidal crystals, such as opals, display bright and iridescent colors when assembled from submicron particles. While the brightness and purity of iridescent colors are well suited for ornaments, signaling, and anticounterfeiting, their angle dependence limits the range of their applications. In contrast, colloidal glasses display angle-independent structural color that is tunable by the size and local arrangement of particles. However, the angle-independent color of colloidal photonic glasses usually yields pastel colors that are not vivid due to the disorder in the particle assembly. Here, we report an electrophoretic assembly platform for tuning the level of disorder in the particle system from a colloidal crystal to a colloidal glass. Altering the electric field in our electrophoretic platform allows for deliberate control of the assembly kinetics and thus the level of order in the particle assembly. With the help of microscopy, X-ray scattering, and optical characterization, we show that the photonic properties of the assembled films can be tuned with the applied electric field. Our analyses reveal that angle-independent color with optimum color brightness can be achieved in typical colloidal suspensions when the range of order is at ∼3.2 particle diameters, which is expected at a moderate electric field of ∼15 V mm-1.

Mechanism of structural colors in binary mixtures of nanoparticle-based supraballs

Inspired by structural colors in avian species, various synthetic strategies have been developed to produce noniridescent, saturated colors using nanoparticle assemblies. Nanoparticle mixtures varying in particle chemistry and size have additional emergent properties that affect the color produced. For complex multicomponent systems, understanding the assembled structure and a robust optical modeling tool can empower scientists to identify structure-color relationships and fabricate designer materials with tailored color. Here, we demonstrate how we can reconstruct the assembled structure from small-angle scattering measurements using the computational reverse-engineering analysis for scattering experiments method and use the reconstructed structure in finite-difference time-domain calculations to predict color. We successfully, quantitatively predict experimentally observed color in mixtures containing strongly absorbing nanoparticles and demonstrate the influence of a single layer of segregated nanoparticles on color produced. The versatile computational approach that we present is useful for engineering synthetic materials with desired colors without laborious trial-and-error experiments.

High-Efficiency, Mass-Producible, and Colored Solar Photovoltaics Enabled by Self-Assembled Photonic Glass

Building-integrated photovoltaics is a crucial technology for developing zero-energy buildings and sustainable cities, while great efforts are required to make photovoltaic (PV) panels aesthetically pleasing. This places an urgent demand on PV colorization technology that has a low impact on power conversion efficiency (PCE) and is simultaneously mass-producible at a low cost. To address this challenge, this study contributes a colorization strategy for solar PVs based on short-range correlated dielectric microspheres, i.e., photonic glass. Through theoretical studies, first we demonstrate that the photonic glass self-assembled by high-index microspheres could enable both colored solar cells and modules, with easily variable colors and negligible parasitic absorption. By a fast spray coating process of colloidal monodisperse ZnS microspheres, we show the photonic glass layer could be easily deposited on silicon solar cells, enabling them to have structural colors. Through varying microsphere sizes, solar cells with different colors are achieved, showing low PCE loss compared to normal black cells. These colored solar cells are also encapsulated with a general lamination process to produce PV modules with various colors and patterns at a stunning PCE approaching 21%. Moreover, the long-term stability is subsequently verified by aging tests including an outdoor exposure for 10 days and a damp-heat test for 1000 h, and the mass producibility is demonstrated by presenting a colored PV panel with an output power over 108 W. These results confirm photonic glass as a promising strategy for colored PVs possessing high efficiency and practical applicability.