Electrochromic devices and thin film transistors from a new family of ethylenedioxythiophene based conjugated polymers

Abstract

New electrochromic conjugated polymers and their corresponding devices based on EDOT (ethylenedioxythiophene) are described. The best of these polymers display response times on the order of 1s and high switchable contrast in the visible and near-infrared (Vis-NIR) spectral regions. Thin films (70 nm) of these new polymers displayed optical band gaps on the order of 1.73 eV (7a) < 2.19 eV (7b) < 2.23 eV (7c) < 2.31 eV (4) < 2.34 eV (2) as calculated from their extrapolation of the absorption edges. Polymers 4 and 7a show field effect hole mobilities of ca. 6.7 × 10⁻⁵ cm² V⁻¹s⁻¹ (on/off ratio 10⁴) and 2.5 × 10⁻⁵ cm² V⁻¹s⁻¹ (on/off ratio10³), respectively, related to their highly ordered inter-chain packing as confirmed by XRD analyses of polymer 4. Electrochromic characterizations show that polymers 7a–c exhibit significant absorption changes in the infrared at low voltage. The resulting solid-state devices offer promise for electrochromic shutters and filters in the IR, since their high charge transfer mobility and ion injection efficiency permits relatively rapid switching and good switchable contrast, while their robustness exceeds that of aqueous devices.