Ion gels comprising ABA triblock copolymers and ionic liquids have received much attention as functional materials in numerous applications, especially as gate dielectrics in organic transistors. Here we have expanded the functionality of ion gels by demonstrating low-voltage, flexible electrochemiluminescent (ECL) devices using patterned ion gels containing redox-active luminophores. The ECL devices consisted only of a 30 μm thick emissive gel and two electrodes and were fabricated on indium tin oxide-coated substrates (e.g., polyester) simply by solution-casting the ECL gel and brush-painting a top Ag electrode. The triblock copolymer employed in the gel was polystyrene-block-poly(methyl methacrylate)-block-polystyrene, where the solvophobic polystyrene end blocks associate into micellar cross-links in the versatile ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]). An ECL gel containing ~6.25 wt % Ru(bpy)3Cl2 (relative to [EMI][TFSI]) as the luminophore turned on at an AC peak-to-peak voltage as low as 2.6 V (i.e., -1.3 to +1.3 V) and showed a relatively rapid response (sub-ms). The wavelength of maximum emission was 610 nm (red-orange). With the use of an iridium(III) complex, Ir(diFppy)2(bpy)PF6 [diFppy = 2-(2',4'-difluorophenyl)pyridine; bpy = 2,2'-bipyridyl], the emitting color was tuned to a maximum wavelength of 540 nm (green). Moreover, when a blended luminophore system containing a 60:40 mixture of Ru(bpy)3(2+) and Ir(diFppy)2(bpy)(+) was used in the emissive layer, the luminance of red-orange-colored light was enhanced by a factor of 2, which is explained by the generation of the additional excited state Ru(bpy)3(2+)* by a coreactant pathway with Ir(diFppy)2(bpy)(+)* in addition to the usual annihilation pathway. This is the first time that enhanced ECL has been achieved in ion gels (or ionic liquids) using a coreactant. Overall, the results indicate that ECL ion gels are attractive multifunctional materials for printed electronics.

Ion gels composed of a copolymer and a room temperature ionic liquid are versatile solid-state electrolytes with excellent features including high ionic conductivity, nonvolatility, easily tunable mechanical properties, good flexibility and solution processability. Ion gels can be functionalized by incorporating redox-active species such as electrochemiluminescent (ECL) luminophores or electrochromic (EC) dyes. Here, we enhance the functionality of EC gels for realizing multicolored EC devices (ECDs), either by controlling the chemical equilibrium between a monomer and dimer of a colored EC species, or by modifying the molecular structures of the EC species. All devices in this work are conveniently fabricated by a "cut-and-stick" strategy, and require very low power for maintaining the colored state [i.e., 90 μW/cm(2) (113 μA/cm(2) at -0.8 V) for blue, 4 μW/cm(2) (10 μA/cm(2) at -0.4 V) for green, and 32 μW/cm(2) (79 μA/cm(2) at -0.4 V) for red ECD]. We also successfully demonstrate a patterned, multicolored, flexible ECD on plastic. Overall, these results suggest that gel-based ECDs have significant potential as low power displays in printed electronics powered by thin-film batteries.

The functionality of ion gels can be enhanced by incorporating different types of redox-active species. Here, we have expanded the functionality of ion gels composed of polystyrene-block-poly(methyl methacrylate)-block-polystyrene and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide to include electrochromism by adding an electrochromic (EC) redox molecule, methyl viologen. Ferrocene was also added to the EC gel as an anodic species. The EC gel was inserted between two indium−tin oxide-coated glass slides (or plastic sheets) to make a simple two-terminal electrochromic device (ECD). The ECD changed color upon application of 0.7 V. The coloration efficiency (η) was 105 cm 2 /C, and the ECD exhibited good operational stability over 24 h even in air. Because the EC gel is processed from common solvents (acetone) at room temperature, it can be coated onto plastic straightforwardly, and we demonstrated a patterned flexible ECD. Overall, the results demonstrate that sub-1 V, flexible ECDs based on EC ion gels can be prepared by simple solution processing, and thus, they are potentially attractive components for printed electronics.

The primary technology of next‐generation wearable electronics pursues the development of highly deformable and stable systems. Here, nonvolatile, highly transparent, and ultrastretchable ionic conductors based on polymeric gelators [poly(methyl methacrylate‐ran‐butyl acrylate), PMMA‐r‐PBA] and ionic liquids (IL) are proposed. A crucial strategy in the molecular design of polymer gelators is copolymerization of PMMA and IL‐insoluble low glass transition temperature (Tg) polymers that can be deformed and effectively dissipate applied strains. Highly stretchable (elongation limit ≈850%), mechanically robust (elastic modulus ≈3.1 × 105 Pa), and deformation durable (recovery ratio ≈96.1% after 500 stretching/releasing cycles) gels are obtained by judiciously adjusting the molecular characteristics of polymer gelators and gel composition. An extremely simple “ionic” strain sensory platform is fabricated by directly connecting the stretchable gel and a digital multimeter, exhibiting high sensitivity (gauge factor ≈2.73), stable operation (>13 000 cycles), and nonvolatility (>10 d in air). Moreover, the skin‐type strain sensor, referred to as ionoskin, is demonstrated. The gels are attached to a part of the body (e.g., finger, elbow, knee, or ankle) and various human movements are successfully monitored. The ionoskin renders the opportunity to achieve wearable ubiquitous electronics such as healthcare devices and smart textile systems.

Voltage-tunable multicolor electrochromic devices (ECDs) are fabricated based on flexible ion gels consisting of copolymers and ionic liquids as an electrolyte layer. Dimethyl ferrocene (dmFc) is incorporated into the gel, which serves as an anodic species. In this study, two electrochromic (EC) materials, monoheptyl viologen (MHV) and diheptyl viologen (DHV), are employed and show significantly different EC behavior despite the similar chemical structure. Both MHV- and DHV-containing ECDs are slightly yellowish in the bleached state, whereas the colored states are magenta and blue, respectively. All devices have good coloration efficiency of 87.5 cm/C (magenta) and 91.3 cm/C (blue). In addition, the required power of ∼248 μW/cm (magenta) and ∼72 μW/cm (blue) to maintain the colored state put the ion gel-based ECDs in a class of ultralow power consumption displays. On the basis of the distinct difference in the coloration voltage range between MHV and DHV, and the rubbery character of the gel, flexible ECDs showing multiple colors are demonstrated. These results imply that voltage-tunable multicolor ECDs based on the gel are attractive to functional electrochemical displays.

Dual-function electrochromic supercapacitors (ECSs) that indicate their real-time charge capacity in color are fabricated using tungsten trioxide (WO 3 ) and Lidoped ion gels containing hydroquinone (HQ). The ECSs can simultaneously serve as either electrochromic devices or supercapacitors. The coloration/bleaching and charging/ discharging characteristics are investigated between 0 and −1.5 V. At the optimal HQ concentration, large transmittance contrast (∼91%), high coloration efficiency (∼61.9 cm 2 /C), high areal capacitance (∼13.6 mF/cm 2 ), and good charging/discharging cyclic stability are achieved. Flexible ECSs are fabricated on plastic substrates by exploiting the elastic characteristics of the gel electrolytes, and they exhibit good bending durability. Moreover, practical feasibility is evaluated by demonstrating the use of the ECSs as an energy storage device and a power source.

Herein, high-performance, reliable electrochromic supercapacitors (ECSs) are proposed based on tungsten trioxide (WO3) and nickel oxide (NiO) films. To maximize device performance and stability, the stoichiometric balance between anode and cathode materials is controlled by carefully adjusting the thickness of the anodic NiO film while fixing the thickness of WO3 to ∼660 nm. Then, a small amount (≤10 mol %) of metal (e.g., copper) is doped into the NiO film, improving the electrical conductivity and electrochemical activity. At a Cu doping level of 7 mol %, the resulting ECS exhibited the highest performance, including a high areal capacitance (∼14.9 mF/cm2), excellent coulombic efficiency (∼99%), wide operating temperature range (0–80 °C), reliable operation with high charging/discharging cyclic stability (>10,000 cycles), and good self-discharging durability. Simultaneously, the change in transmittance of the device is well synchronized with the galvanostatic charging/discharging curve by which the real-time energy storage status is visually indicated. Furthermore, the practical feasibility of the device is successfully demonstrated. These results imply that the ECS fabricated in this work is a promising potential energy storage platform and an attractive component for future electronics.

We synthesized, via anionic coupling reaction, poly(3-dodecylthiophene)-block-poly(methyl methacrylate) copolymers (P3DDT-b-PMMA) having narrow molecular weight distribution and several block compositions. P3DDT was chosen because of moderate rod/rod interaction compared with a weak interaction of poly(3-(2′-ethyl)hexylthiophene) (P3EHT) or a strong interaction of poly(3hexylthiophene) (P3HT). The moderate rod/rod interaction of P3DDT enables us to investigate final morphologies affected by crystallization arising from the rod/rod interaction of P3DDT or the microphase separation between P3DDT and PMMA blocks. When the weight fraction (w P3DDT ) of P3DDT block of P3DDT-b-PMMAs was smaller than ∼0.6, various microdomains such as body-centered-cubic spheres, hexagonally packed cylinders, and lamellae were observed similar to those reported in conventional coil−coil type block copolymers. Interestingly, these microdomains were maintained even after P3DDT blocks were crystallized, indicating that P3DDT crystals were successfully confined within P3DDT microdomains. On the other hand, when w P3DDT was high (e.g., w P3DDT ∼ 0.76), the rod/rod interaction became dominant over microphase separation between two blocks. As a result, only fibril structure was found after the crystallization of P3DDT block.