Near-infrared and multicolor electrochromic device based on polyaniline derivative

Electroactive conducting copolymers of aniline (ANI) and diphenylamine (DPA) are prepared on indium tin oxide (ITO) surface from 1 mol/L H ₂SO₄ aqueous solution with different feed ratios of ANI to DPA by using a potentiostatic method. FTIR spectra and SEM measurements are used to confirm the formation of copolymers. Due to the combination of the N,N-diphenyl benzidine and aniline units in the molecular chain, the copolymer films exhibit improved electrochemical and electrochromic properties, compared to PANI and PDPA. The copolymer [marked as P(ANI9-co-DPA1)] film prepared at a ratio of 9:1 (ANI/DPA) exhibits novel transmittance modulation both in visible and near-infrared (NIR) region between -0.8 V and 0.8 V (52% and 67% respectively) and fast response time (3.6 s for coloration and 2.3 s for bleaching at 600 nm). An electrochromic device (ECD) based on P(ANI9-co-DPA1) and PEDOT:PSS is also fabricated and shows a multicolor electrochromic performance, with a good optical contrast (29% in visible region and 40% in NIR region), acceptable response time (8.3 s for coloration and 7.5 s for bleaching at 600 nm) and long-term stability. Clear color changes from transparent (-0.8 V), bright green (0 V), seagreen (0.4 V) to dark slate gray (0.8 V) are demonstrated.