Synthesis of ordered bowl-like polyaniline film with enhanced electrochromic performances

A bowl-like polyaniline (PANI) film is synthesized by the combination of electrodeposition and monolayer colloidal crystal template (MCCT). The resulting film exhibits an ordered hexagonal close-packed bowl-like arrangement that is made up of macrobowls with a diameter of 450 nm. The unique bowl-like structure endows PANI film with enhanced electrochromic performances due to its increased accessible intercalation sites originating from larger surface areas and shortened diffusion distances of ions resulting from macroporous structure. It is found that the bowl-like PANI film possesses faster switching responses (1.45 s for coloration and 0.62 s for bleaching), larger optical transmittance modulation (52.1% at 740 nm) and higher coloration efficiency (118.2 cm²C⁻¹) than the dense PANI film prepared without the MCCT. Moreover, the bowl-like film also exhibits IR electrochromic performances in the wavelength range from 2.5–25 μm, which depicts a reflectance modulation ∼ 36.5% at 10 μm. This work provides a promising strategy for constructing other bowl-like polymer electrochromic films.