Transparent displays have emerged as a class of cutting-edge electronics. Here, we propose user-customized, design-it-yourself (DIY) transparent displays based on electrochromic (EC) ion gels including viologens. To achieve multiple colors and enhance the functionality of EC displays (ECDs), the incorporation of several EC chromophores is inevitable. However, the issue related to the discrepancy of coloration voltages is inherent due to the different electrochemical characteristics of each material, causing unbalance of the color contrast. To overcome this problem without significantly affecting the performance of ECDs, we suggest a simple but effective strategy by adjusting the oxidation activity of electrolyte-soluble anodic species (i.e., ferrocene (Fc) derivatives) by modifying pendant groups. We systematically investigated the effects of the employed Fc derivatives on the EC behaviors of ECDs in terms of the coloration voltage, maximum transmittance contrast, device dynamics, coloration efficiency, and operational stability. We determine the conditions for implementing red-green-blue (RGB) colors with comparable intensities at similar voltages. Last, we draw images using RGB EC inks for conceptual demonstration of the DIY transparent displays. The fabricated ECDs exhibit transparent bleached states and user-customized images in the colored states. Overall, this result implies that the extremely simple DIY ECDs, which do not require conventional lithography or printing, have great potential as future transparent displays that can be easily customized.

Ion gels consisting of room-temperature ionic liquids and polymer gelators are considered attractive solid-state electrolyte platforms for functional electrochemical applications due to their tunable electrochemical/mechanical properties, nonvolatility even in a vacuum, and compatibility with various solution processes. Accordingly, a number of studies have been reported on improving the functionality of ion gels and their use in diverse applications. In this Perspective, we highlight recent representative advances in the development of functional gels based on judiciously designed copolymer gelators or prepared by incorporating redox species. In addition, we introduce versatile applicability of ion gels in a variety of applications including electrochemical displays, smart sensory systems, and energy generation/storage systems.

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Electrochromic (EC) energy storage devices represent a cutting‐edge technology visually indicating stored energy status in real time through color change. Herein, extremely simple single‐layer electrochromic supercapacitors (SL‐ECSs) based on energy storage EC ion gels are proposed. The operation of SL‐ECSs follows Fick's law because of the diffusive nature of mass transport of all redox species. Therefore, the diffusion dynamics are tuned by tailoring fundamental parameters, the diffusion coefficient, and concentration gradient, and the availability of energy storage is maximized by reducing residual charges that cannot be extracted during the normal discharge process. In terms of the two critical metrics of ECSs, areal capacitance (Careal) and transmittance contrast between charged and discharged states (ΔT), the performance of SL‐ECSs (Careal ≈ 43.0 mF cm–2 and ΔT ≈ 96.8%) is favorably compared with previously reported ECSs. The capacitance retention remains at >80% even after continuous charge/discharge cyclic operations for 3000 min without specific encapsulation. Moreover, the practical multi‐functionality of the SL‐ECS is successfully demonstrated as a power source and applied force monitoring platform. It is expected that the SL‐ECS will be a simple but versatile component of high‐performance, ultra‐small functional electronics.

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