The increasing efforts devoted to fabricating electrochromic (EC) devices have motivated a lot of studies to develop new EC materials. Herein, we introduce two poly(phenothiazine)-type redox active polymer films as new EC materials. Poly(methylene blue) (PMB) and poly(thionine) (PTH) films were electrochemically deposited onto the transparent fluorine-doped tin oxide (FTO) electrode modified with multi-walled carbon nanotubes (MWCNTs), which are named as FTO/MWCNTs/PMB and FTO/MWCNTs/PTH, respectively. The as-prepared polymer films were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR), cyclic voltammetry (CV), and spectroelectrochemical techniques. Both polymer films exhibited EC behavior at approximately 600 nm. PMB and PTH films are blue and pale purple, respectively, in the oxidized state and change their color to colorless, if reduced at − 0.6 V. In particular, FTO/MWCNTs/PMB showed a satisfactory ΔT (24%) at 600 nm. The obtained results demonstrate that PMB and PTH, as derivatives of phenothiazine dyes, can be introduced as novel EC materials.
