The tunable optoelectronic performances of EDOT-benzene-based hybrid electrochromic polymers with different methoxy groups

Abstract

As an electron donor group, alkoxy was very effective in improving the optoelectronic properties of conjugated polymers. To investigate the impact of incorporating alkoxy groups on the electrochromic characteristics of hybrid electrochromic polymers, in the course of this study, three methoxylated monomers, namely EOMeE, E2OMeE, and EMeE, were readily synthesized via the Stille coupling reaction. The fabrication of the respective methoxylated polymers, specifically P(EOMeE) and P(E2OMeE), was accomplished utilizing the electrochemical deposition method. Subsequently, a comprehensive investigation was conducted to analyze their molecular configurations, optical characteristics, electrochemical behavior, and electrochromic attributes. Notably, aside from EMeE, which is challenging to electro-polymerize into stable films, the other two methoxylated monomers exhibit low initial oxidation potentials ranging from 0.55 to 0.6 V. This feature is highly advantageous for fabricating high-quality electrochromic polymers at reduced potentials. With the increase of methoxy substitution numbers, the ultraviolet and fluorescence of the monomer have a certain degree of red shift trend, accompanied by the decrease of fluorescence quantum yield. As prepared methoxylated polymer also possesses excellent redox activity and outstanding redox stability. It is marked by reliably high and steady variations in transmittance throughout the near-infrared range, in conjunction with excellent optical stability and a beneficial memory effect. Concurrently, the addition of methoxy groups markedly decreases the response time of the hybrid methoxylated polymers to below 1 s and preserves a high coloration efficiency of over 164.52 cm² C⁻¹ across the full wavelength range. These findings suggest that the synthesized methoxylated hybrid polymers are highly promising for use in electrochromic devices.