Highly oriented lamellar polyaniline with short-range disorder for enhanced electrochromic performance

Conjugated organic polymers (COP) are fundamental for the future development of electrochromic devices. Despite the progress of composite materials, the electrochromic performance of pristine COP is still limited by dense three-dimensional (3D) structure. This work reports the fabrication of high optical contrast polyaniline (PANI) films with fast switching speed by electrochemical polymerization. Benefitting from the stereo-structure and size of p-toluenesulfonic acid (pTSA), highly oriented lamellar polyaniline with nanoscale large inter-layer spacing and a disordered in-plane structure is obtained. These structural factors simultaneously improve ion diffusion capability and optimise reaction area, resulting in a high optical contrast of above 70% at a wavelength of 720 nm, a fast response time (0.8 s for coloring and 4.2 s for bleaching), and remarkable coloration efficiency (328.5 cm2 C−1). In addition, the pTSA-PANI quasi-solid-state electrochromic device displayed good electrochromic performance with optical contrast of 82%, suggesting an inherent suitability for use in electrochromic fields. Furthermore, the synthetic method developed here represents a new and simple technique to modulate photoelectronic properties.