Tailoring NIR/IR-Light Absorbing Conjugated Polymers for Mechanically and Environmentally Robust Electrochromic Devices

Project: Research project

Project Details

Description

Conjugated polymers allow for the facile tuning of key properties for electrochromic (EC) devices, including the electronic, optical, and physical, e.g. mechanical and processability, through the incorporation of various functional groups and substituents. Despite this enhanced tunability, many conjugated polymers used for EC applications maintain their primary absorption within the visible region (e.g. 400-780 nm). Although switching at these wavelengths is useful for various applications, e.g. smart windows and displays, switching in the NIR/IR (e.g. 780-2500 nm) could allow for utility in optical communication devices and thermal energy control in buildings or aircrafts. While there are reports of conjugated polymers with switching in the NIR/IR, many of these materials have not been evaluated for their mechanical stability or integrated into flexible EC devices containing a dynamic optical filter where multiple polymers with varying absorption properties are incorporated into a single device.
Recently, we have disclosed the fabrication of porous conjugated polymer thin-films for use in organic thin-film transistors (OTFTs), gas sensors, and organic electrochemical transistors (OECTs) using a breath-figure patterning process. This process was further optimized for the fabrication of porous, conjugated polymer films with a uniform honeycomb structure that are mechanically and electrochemically robust when incorporated into OECTs using a flexible substrate. The functionalized diketopyrrolopyrole (DPP) and bithiophene copolymers used in the aforementioned OECT devices possess absorption near the NIR region. The optical properties of these polymers could potentially be further tuned through structural modification to allow for the fabrication of EC devices with NIR/IR switching that are also mechanically and electrochemically robust. Herein, we propose the design, synthesis, and the fabrication of breath-figure derived honeycomb structured conjugated polymers for EC device applications.
By computationally screening polymer structures of interest to focus our synthetic efforts, we plan to target DPP and indolo-napthyridine-6,13-dione (IND) containing conjugated polymers with NIR/IR absorption. Polymers containing these comonomers were selected due to their previous use in flexible electronics or their desirable absorption and charge transport properties based off of literature precedent. We propose that the breath-figure derived honeycomb structures containing these polymers would allow for the fabrication of flexible EC devices without compromising operational stability, and that this method of fabrication could allow for the layering of different EC polymers with varying optical properties to generate a dynamic optical switch. We also propose that the honeycomb structure would allow for the continuous penetration of the electrolyte within the EC device into the conjugated polymer film to allow for uninhibited operation even when subjected to extreme mechanical stress or when multiple layers of conjugated polymer films are present. Thorough testing of the mechanical properties and environmental stability would allow for further structural
StatusActive
Effective start/end date10/1/219/30/23

Funding

  • Office of the Director of National Intelligence (Marks AGMT 9/21/22)

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