Large, Switchable Electrochromism in the Visible Through Far-Infrared in Conducting Polymer Devices

Abstract

Advanced materials with large and dynamic variation in thermal properties, sought for urgent defense and space applications, have heretofore been elusive. Conducting polymers (CPs) have shown some intrinsic variation of mid‐ to far‐infrared (IR) signature in this respect, but the practical utilization of this has remained elusive. We report herein the first significant IR electrochromism in any material, to our knowledge, in the 0.4 through 45 μm region. This is seen in practical CP devices in the form of thin (<0.5 mm), flexible, entirely solid‐state, variable area (1 cm2 to 1 m2) flat panels. Typical properties include: very high reflectance variation; switching times <2 s; cyclabilities of 105 cycles; emittance variation from 0.32 to 0.79; solar absorptance variation from 0.39 to 0.79; operating temperatures of –35 to +85 °C; durability against γ‐radiation to 7.6 Mrad, vacuum to 10–6 torr, and simulated solar wind (e.g., 6.5 × 1016 e/cm2 @ 10 keV).

An MD Study of the Applicability of the Walden Rule and the Nernst–Einstein Model for Ionic Liquids

“…The slow switching speeds and difficult processing techniques of inorganic compounds such as tungsten oxide (WO 3 ) for infrared applications16 can be improved by using conjugated polymers, although relatively few investigations have explored the electrochromic properties of conjugated polymers in the mid or far infrared. Furthermore, the applications pursued thus far have been reflection mode devices for application such as emissivity modulators 11, 15, 17, 18. We chose to investigate P3HT as a transmission‐based mid‐infrared electrochromic material because it is a relatively stable conducting polymer that is easily processed with properties that have been extensively investigated for applications ranging from solar cells to transistors 19–21.…”

Matched‐dual‐polymer electrochromic lenses, using new cathodically coloring conducting polymers, with exceptional performance and incorporated into automated sunglasses

“…One simple means of increasing the switching speed (and the evenness of the switching) is to apply an overvoltage to the system. For example, in the poly(aniline) IR electrochromics described by Chandrasekhar et al where the recommended applied voltage for stable switching within the redox stability limits is +/−1.1 V, the applied voltage may be increased to, for example, +/−2.0 V or +/−3.0 V or even +/−4.0 V. However, one would invariably risk irreversible damage to the electrochromic system, with perhaps only a marginal increase in the switching speed (reduction in switching time). Then, after a few such switches, the electrochromic device would essentially stop functioning.…”

“…Here, it is seen that, for polymer films having nearly identical equivalent charge during deposition, the voltammogram for the copolymer device is more well defined and has significantly higher currents than that for the P(Cl‐Bz‐ProDOT)‐only device. This implies that more of the polymer in the former case is electroactive and switching. These CVs show that the copolymer is a better match for the aromatic amine than poly(Cl‐Bz‐ProDOT) alone.…”

“…(Reflectance‐mode, i.e., mirror‐like, visible‐region electrochromics based on CPs have been in commercial use for some time now, for example, as implemented in automobile rearview mirrors by Gentex, among other very limited uses . In further contrast, reflectance‐mode, IR‐region electrochromics based on CPs, for military camouflage, spacecraft thermal control, and related applications, have been marketed for some years now …”

Substituent and heteroatom effects on the electrochromic properties of similar systems

“…Electrochromism is defined as a visible color change under external applied potentials, which is one of the most important properties of conjugated polymers and thanks to easy synthesis and tunable intrinsic properties (i.e., electrical and optical), a lot of distinct and saturated colors like blue,1–3 green,3–7 and black8–10 were reported in the neutral state. These features make them promising candidates for displays,11 smart windows,12, 13 electrochromic devices,14–16 mirrors,17, 18 and camouflage materials 19–21. Among organic electrochromic polymers, polythiophenes and their alkylenedioxythiophene derivatives22 have attracted considerable interest because of their multicolor changes in the same structure, long cycle life, high optical contrast ratio, film forming properties as well as fast switching time, and low operation voltage, when compared to inorganic materials and other polymers.…”