Redox-Active Macrocycles for Organic Rechargeable Batteries.

Organic rechargeable batteries, composed of redox-active molecules, are emerging as candidates for the next generation of energy storage materials because of their large specific capacities, cost effectiveness, and the abundance of organic precursors, when compared with conventional lithium-ion batteries. Although redox-active molecules often display multiple redox states, precise control of a molecule's redox potential, leading to a single output voltage in a battery, remains a fundamental challenge in this popular field of research. By combining macrocyclic chemistry with density functional theory calculations (DFT), we have identified a structural motif that more effectively delocalizes electrons during lithiation events in battery operations-namely, through-space electron delocalization in triangular macrocyclic molecules that exhibit a single well-defined voltage profile-compared to the discrete multiple voltage plateaus observed for a homologous macrocyclic dimer and an acyclic derivative of pyromellitic diimide (PMDI). The triangular macrocycle, incorporating three PMDI units in close proximity to one another, exhibits a single output voltage at 2.33 V, compared with two peaks at (i) 2.2 and 1.95-1.60 V for reduction and (ii) 1.60-1.95 and 2.37 V for oxidation of the acyclic PMDI derivative. By investigating the two cyclic derivatives with different conformational dispositions of their PMDI units and the acyclic PMDI derivative, we identified noticeable changes in interactions between the PMDI units in the two cyclic derivatives under reducing conditions, as determined by differential pulse voltammetry, solution-state spectroelectrochemistry, and variable-temperature UV-Vis spectra. The numbers and relative geometries of the PMDI units are found to alter the voltage profile of the active materials significantly during galvanostatic measurements, resulting in a desirable single plateau for the triangular macrocycle. The present investigation reveals that understanding and controlling the relative conformational dispositions of redox-active units in macrocycles are key to achieving high energy density and long cycle-life electrodes for organic rechargeable batteries.

PEDOT:PSS "Wires" Printed on Textile for Wearable Electronics.

Herein, the fabrication of all-organic conductive wires is demonstrated by utilizing patterning techniques such as inkjet printing and sponge stencil to apply poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) onto nonwoven polyethylene terephthalate (PET) fabric. The coating of the conducting polymer is only present on the surface of the substrate (penetration depth ∼ 200 µm) to retain the functionality and wearability of the textile. The wires fabricated by different patterning techniques provide a wide range of resistance, i.e., tens of kΩ/□ to less than 2 Ω/□ that allows the resistance to be tailored to a specific application. The sheet resistance is measured to be as low as 1.6 Ω/□, and the breakdown current is as high as 0.37 A for a 1 mm wide line. The specific breakdown current exceeds the previously reported values of macroscopic carbon nanotube based materials. Simple circuits composed of the printed wires are demonstrated, and resistance of the circuit from the measurement agrees with the calculated value based on Kirchhoff's rules. Additionally, the printed PEDOT:PSS wires show less than 6.2% change in sheet resistance after three washing and drying cycles using detergent.

Color-tuning neutrality for flexible electrochromics via a single-layer dual conjugated polymer approach.

A method to color-tune electrochromic devices through the use of theoretical calculations is demonstrated to achieve neutrality using only three monomers that form two distinct copolymers. These devices exhibit photopic contrasts up to ca. 38%, high neutrality, color uniformity, and switch speeds of less than 1 s. In addition, this method is used to fabricate a large-area flexible electrochromic device of 75 cm(2) , exceeding the size of small displays.

Neutral color tuning of polymer electrochromic devices using an organic dye.

Herein, we present a facile, one-step method to color tune electrochromic devices (ECDs) that switch between two neutral colors via in situ electrochemical polymerization of electroactive monomers in the presence of a small molecule organic yellow dye using all commercially available materials. These devices exhibited photopic contrasts of ca. 30% without background correction when assembled on flexible PET-ITO substrates. In addition, devices exhibited switching speeds as low as 1 second, color uniformity, and stability. Large defect free ECDs of 100 cm(2) were fabricated exceeding the active switch area required for goggles, lenses, and small display applications.

Acrylated poly(3,4-propylenedioxythiophene) for enhancement of lifetime and optical properties for single-layer electrochromic devices.

We utilized our in situ method for the one-step assembly of single-layer electrochromic devices (ECDs) with a 3,4-propylenedioxythiophene (ProDOT) acrylate derivative, and long-term stability was achieved. By coupling the electroactive monomer to the cross-linkable polymer matrix, preparation of the electrochromic ProDOT polymer can occur followed by UV cross-linking. Thus, we achieve immobilization of the unreacted monomer, which prevents any degradative processes from occurring at the counter electrode. This approach eliminated spot formation in the device and increased stability to over 10 000 cycles when compared to 500 cycles with conventional ProDOT devices wherein the monomer is not immobilized. The acrylated electrochromic polymer exhibits similar electrochromic properties as conventional ProDOT devices, such as photopic contrast (48% compared to 46%) and switch speed (both 2 s). This method can be applied to any one-layer electrochromic system where improved stability is desired.

Solid-state high-throughput screening for color tuning of electrochromic polymers.

Diffusion of two monomers and their oxidative copolymerization inside a solid-state gel electrolyte is utilized as a method to match the monomer feed ratio to a color resulting from a conjugated copolymer having a single absorption in the visible region. Here, a combination of two monomers is used to generate a solid-state electrochromic device of any color, except black and green, in the colored state with all other colors going to transmissive sky blue in the bleached state.