Optical-Cavity-Incorporated Colorful All-Solid-State Electrochromic Devices for Dual Anti-Counterfeiting.

The fusion of electrochromic technology with optical resonant cavities presents an intriguing innovation in the electrochromic field. However, this fusion is mainly achieved in liquid electrolyte-based or sol-gel electrolyte-based electrochromic devices, but not in all-solid-state electrochromic devices, which have broader industrial applications. Here, a new all-solid-state electrochromic device is demonstrated with a metal-dielectric-metal (MDM) resonant cavity, which can achieve strong thin-film interference effects through resonance, enabling the device to achieve unique structural colors that have rarely appeared in reported all-solid-state electrochromic devices, such as yellow green, purple, and light red. The color gamut of the device can be further expanded due to the adjustable optical constants of the electrochromic layer. What is more, this device exhibits remarkable cycling stability (maintaining 84% modulation capability after 7200 cycles), rapid switching time (coloration in 2.6 s and bleaching in 2.8 s), and excellent optical memory effect (only increasing by 13.8% after almost 36 000 s). In addition, this exquisite structural design has dual-responsive anti-counterfeiting effects based on voltage and angle, further demonstrating the powerful color modulation capability of this device.

Semiconductor SERS on Colourful Substrates with Fabry-Pérot Cavities.

Non-metallic materials have emerged as a new family of active substrates for surface-enhanced Raman scattering (SERS), with unique advantages over their metal counterparts. However, owing to their inefficient interaction with the incident wavelength, the Raman enhancement achieved with non-metallic materials is considerably lower with respect to the metallic ones. Herein, we propose colourful semiconductor-based SERS substrates for the first time by utilizing a Fabry-Pérot cavity, which realize a large freedom in manipulating light. Owing to the delicate adjustment of the absorption in terms of both frequency and intensity, resonant absorption can be achieved with a variety of non-metal SERS substrates, with the sensitivity further enhanced by ≈100 times. As a typical example, by introducing a Fabry-Pérot-type substrate fabricated with SiO2 /Si, a rather low detection limit of 10-16  M for the SARS-CoV-2S protein is achieved on SnS2 . This study provides a realistic strategy for increasing SERS sensitivity when semiconductors are employed as SERS substrates.

Electrochromic Metamaterials of Metal-Dielectric Stacks for Multicolor Displays with High Color Purity.

Inorganic electrochromic (EC) materials with vibrant multicolor change that are compatible with large-scale processing have been at the forefront of EC technology and are crucial in a wide range of applications, such as displays and camouflage. However, limited strategies are available to realize such inorganic materials, and challenges such as low color purity are yet to be overcome. Here, we demonstrate multilayered metal-dielectric metamaterials (MMDMs) as a new family of inorganics-based EC materials to achieve dynamic alternation among multicolors with high contrast and high color purity, which are structurally realized by significantly enhancing the confinement of the incident light in specific optical frequencies. This multilayer structure renders high reflectivity (75%), high quality factor (7.4), and a full width at half-maximum of 60 nm before coloration and presents a color gamut at least 40% wider than that of previously reported metamaterials after coloration, indicating good color quality.