Multicolor electrochromic films based on 2,2’:5′,2″-trithiophene and indole-6-carboxylic acid

The copolymer P(TT -co- ICA) was prepared with different ratio of 2,2’:5′,2″-trithiophene (TT) and indole-6-carboxylic acid (ICA) via the potentiostatic method. The film structure was characterized by using field emission scanning electron microscopy (FE-SEM), ultraviolet-visible (UV-vis) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The electrochemical and electrochromic properties were investigated through chromametry, cyclic voltammetry (CV), and spectroelectrochemical techniques. The P(TT -co- ICA) achieves a color difference (ΔE) of 85.19, substantially higher than the 12.30 observed for the PICA. The optical bandgap of P(TT -co- ICA) (2.43-2.49 eV) is lower than that of PICA (2.52 eV). P(TT -co- ICA) exhibited excellent color modulation capability, displaying reversible transitions between orange-yellow, gray-green, and blue-gray at different applied potentials. Furthermore, P(TT -co- ICA) demonstrates superior optical contrast (35.6–56.8%), high coloration efficiency (127–252 cm 2 /C), and satisfactory cycling stability (53–78% retention). These findings indicate that the incorporation of the TT monomer effectively enhances both the color difference and electrochromic performance of the P(TT -co- ICA) , establishing it as a promising candidate material for electrochromic applications.