Ultrahigh cycling stability and wide infrared modulation of electrochromic devices based on electrodeposited triphenylamine cross-linked polyaniline derivatives

Reflective electrochromic devices (RECDs) based on polyaniline (PANI) have garnered significant attention due to their broad-band modulation capabilities. However, the inherent unstable molecular structure of PANI remains a major challenge, affecting both its cycling stability and modulation range. To address this issue, triphenylamine and m -phenylenediamine were introduced to prepare cross-linked PANI (CPANI) electrochromic thin films via a straightforward electrodeposition process in this paper. The thermal-infrared emissivity modulation range of the CPANI-based RECD (C-RECD) achieved great improvement in the atmospheric windows of 3-5 and 8-14 μm, with a maximum emissivity modulation range of 0.5 and 0.7, respectively. Remarkably, the C-RECD exhibits exceptional cycling stability, enduring up to 10 000 cycles, while maintaining a 70% average emissivity modulation range after cycling. The excellent modulation capability and cycling stability of the C-RECD break the record of the PANI-based RECDs. The theoretical calculations, in situ Raman spectroscopy, and emittance spectra were examined to gain insights into the crosslinking enhancement mechanism. Its distinctive cross-linked structure promotes electron delocalization within the PANI chain, which facilitates an increase in the number of polarons and hinders the formation of local quinoid over-oxidation units, thus effectively improving its emissivity modulation capability and cycling stability. The thermal-infrared images demonstrate the apparent temperature management effects at 7.2 °C and 13.3 °C when the C-RECD is integrated with human skin and a hot plate. This work provides promising opportunities for the production of long-term stable anti-reconnaissance and thermal management devices based on PANI-based RECDs. A flexible C-RECD based on a CPANI electrode is successfully fabricated, exhibiting wide-band electrochromic performance for visible-light color changes and infrared emissivity modulations, with ultrahigh cycling stability for 10 000 cycles.