Scalable, Milliwatt-Level, Switchable Electrochromic Resonator for Full-Color Generation

Abstract

Display is an inseparable device for visually conveying information in today's daily life. Although the conventional color-filter-based light emitting devices have made great progress by the world's leading companies, there is still the important problem of power consumption. Alternatively, reflective displays and/or electronic paper utilize ambient light as a light source, thus, it does not consume energy for light emission, resulting in drastically reduced power consumption. Behind these advantages, electronic paper shows the black and white operation method, which has been treated as a limitation for colorful image production. In recent years, state-of-the-art coloration technologies have been introduced including thin-film cavity, plasmonics, and metasurface . These systems have been combined with functional materials such as liquid crystals, phase change materials, or electrochromic polymers to successfully turn on and off these reflective surfaces. Nevertheless, due to the individual RGB sub-pixel configuration, each color can only occupy up to 1/3 of the total gamut, which not only reduces chromaticity but also requires a lot of incident light. Here, we present full-color electrically tunable reflective display (ETRD) with the milliwatt-level power-consumption. The RGB implementation allowed us to present effective displays with a single reflective pixel with multiple colors (monopixels) instead of relying on adjacent pixels with fixed colors. By introducing planar resonant structure, the scalable and full-colored reflective display is presented over wafer lever. Based on the structural design to have sensitive chromatic responsivity, the refractive-index-engineered/porous meta-medium has been introduced on metal film for the resonance promoting, which shows a great chromatic sensitivity to electrochromic materials. For the active modulation, we used polyaniline (PANI), which show great complex refractive index modulation level, resulting in distinct color modulation over RGB range. In this process, we successfully coated the PANI layer on meta-medium with great uniformity, enabling scalable fabrication. Furthermore, the monopixel configuration is adopted as a display unit pixel for prohibiting degradation of chromaticity. In particular, the protonation reaction of PANI enables the fast/low-voltage operation (from - 0.2 to 0.8V) with comparable switching time (~34 ms). Also, the minimized voltage levels lowered the power consumption as milliwatt-level (≈ 1 mW cm−2). In addition, we designed the pixelated reflective display module, which possesses the addressing ability. Finally, the full-color range switchable device shows a great lifetime over 200 cycles without degradation. In conclusion, we presented an electrically tunable reflective display based on electrochromic material for low power consumption and dynamic colorations. The electrically tunable reflective display with planar configuration provides a wide range of color generation in the reflection mode. We also designed the pixelated display module, which is capable of addressing ability. The investigated ETRD can indeed serve as the highly chromatic display with low-energy consumption striving toward wide color purity as electronic papers or affordable display.