Full-Colored, Large-Area, Electrically Reconfigurable Photonic Resonator with Low-Power Consumption

Abstract

Display technology plays an essential role in effectively delivering visual information in contemporary daily life. Reflective display, which uses external ambient light as a source, can operate without a backlight panel electronic paper, enabling low energy consumption. In the past few years, there have been various approaches implemented to improve the performance of electronic paper (e-paper), particularly in terms of switching time and on/off ratio. As a result, leading electronics companies (e.g., Amazon Kindle) have introduced e-papers with enhanced capabilities. While e-papers serve as excellent display devices, they have certain limitations, such as the necessity of high operating voltages and monochromatic image operation, restricting colorful output. Recently, a new strategy has emerged focusing on the active modulation of plasmonic structural colors based on nanostructured photonic systems. This progress successfully demonstrates the switchable structural colors based on the optically active materials, including phase change materials and conducting polymers, which modulate its complex refractive index by external energy. Especially, conducting polymer, which controls the optical property by an electrochemical redox reaction, has attracted great attention due to its low power consumption. However, the limited complex refractive index and minimal variation levels impede strong interaction between light and matter on plasmonic structures, leading to a diminished ability to express vibrant colors.

In this study, we present the milliwatt-level controllable electrochromic thin-film resonator capable of full-color generation based on polyaniline (PANI). To overcome the low complex refractive index variation level of PANI (Δn ~ 0.6), we designed a highly resonant planar photonic structure based on a refractive index engineered layer on the metal film, resulting in diverse coloration over an entire visible wavelength range. In particular, the electrochemical redox reaction is enabled by the exchange of proton, which controls the doping level of PANI, leading to the fast/efficient modulation of optical properties. The protonation process is achieved in the narrow voltage range from -0.2 V to 0.8 V. The voltage level significantly contributes to low power consumption (~1.32 mW cm-2), which is 20 times lower than commercial displays such as OLED, and even half the power consumption of e-paper. In addition, the active resonant structure based on PANI demonstrates stable reversibility without any degradation over 200 cycles. Moreover, this device achieves a fast-switching time (~34 ms), and also, shows operation capability compared to a commercial video rate of 30 Hz. In conclusion, we present an electrochemically switchable reflective display based on PANI, enabling remarkably efficient and dynamic coloration. We also suggested a passive matrix display module; thus, the pixel-by-pixel control of potential enables diverse pattern generation. We believe that our suggested platform will be utilized as a promising display application including smart windows, electronic wallpapers, attachable displays, and many types of electronics based on its ultra-thin scale, large color space, and low power consumption.