Reversibly controlled infrared transparency of conjugated polymer films incorporated into a compact electrochemical cell structure

We demonstrate a reversible control of the mid-infrared (mid-IR) transparency of conjugated polymer films in a compact electrochemical cell structure with planar IR-transparent electrodes. The mid-IR absorbance of up to more than 1.0 is observed when a 1.0 AM thick polythiophene layer is electrochemically doped with an ionic liquid under variable bias voltage. Furthermore, the doping and dedoping processes can be repeated with reproductive absorbance spectra, in contrast to the conventional one-way chemical doping. Our device structure works for actively variable attenuation filters in the mid-IR region and can also be extended potentially to the terahertz region. (C) 2022 Optica Publishing Group

Automated summary

In this study, we demonstrate the reversible control of mid-infrared transparency in conjugated polymer films using a compact electrochemical cell structure with planar IR-transparent electrodes. By electrochemically doping a 1.0 AM thick polythiophene layer with an ionic liquid under variable bias voltage, we observe mid-IR absorbance of more than 1.0. Unlike conventional one-way chemical doping, our doping and dedoping processes can be repeated with reproducible absorbance spectra. This device structure has potential applications as actively variable attenuation filters in the mid-IR region, and can potentially be extended to the terahertz region.