Colorful E-Paper Based on Inorganic Nanostructures

In recent years, reflective displays have gained a lot of attention due to their low power consumption and excellent visibility in sunlight. The market already offers viable options for reflective displays, mostly based on electrophoretic ink (E-ink). However, this technology has a number of limitations, including poor color quality. Therefore, black-and-white E-ink displays remain the most popular alternative [1].<br/>We have investigated the integration of structural coloration and electrochromic materials for new types of reflective displays in color. We fabricated highly reflective red, green, and blue metasurfaces, based on Fabry-Perót cavities and plasmonics. In order to display dynamic images, we implemented electrochromic materials as on/off shutters [2].<br/>To further improve the overall reflectivity, we aimed to reduce the number of subpixels needed to achieve a wide color gamut. Generally, this subdivision consists of three subpixels, normally red-green-blue. By fabricating a dynamic Fabry-Perót cavity, where one of the layers is made up of electrochromic WO3, we predicted to achieve full color with only two subpixels [3]. In this case, the electrochromic material tunes the resonance of the cavity, which in turn shows several colors depending on the degree of ion intercalation.<br/>Furthermore, commercial alternatives have a slow refresh rate, which makes them unsuitable for displaying videos. To overcome this problem, we have incorporated electrochromic polymers into engineered nanostructures with positive curvature. By optimizing electrolyte and electrode configuration, the switching speed could be improved to the extent needed to enable video display [4].<br/><br/><br/>1. Heikenfeld, J., et al., <i>Review Paper: A critical review of the present and future prospects for electronic paper.</i> Journal of the Society for Information Display, 2011. <b>19</b>(2): p. 129.<br/>2. Gugole, M., et al., <i>High-Contrast Switching of Plasmonic Structural Colors: Inorganic versus Organic Electrochromism.</i> ACS Photonics, 2020.<br/>3. Gugole, M., et al., <i>Electrochromic Inorganic Nanostructures with High Chromaticity and Superior Brightness.</i> Nano Letters, 2021. <b>21</b>(10): p. 4343-4350.<br/>4. Xiong, K., et al., <i>Video Speed Switching of Plasmonic Structural Colors with High Contrast and Superior Lifetime.</i> Advanced Materials, 2021. <b>33</b>(41): p. 2103217.