Triphenylamine-based multielectrochromic material and its neutral green electrochromic devices

A star-shaped monomer tris[4-(3,4-ethylenedioxythiophene)phenyl]amine (TEPA) was successfully synthesized and electrochemically polymerized to obtain a multielectrochromic polymer (PTEPA). The electroactive yellowish green color film converted to green, blue and steel blue in turn upon applied stepwise oxidations from −0.4 to 0.95 V. The UV–vis spectra showed that the dedoped polymer film has two absorption bands located at 448 and 686 nm, respectively, and the optical band gap was calculated to be 1.3 eV. Maximum contrast (ΔT%) and response time of the PTEPA film were measured as 26.84% and 0.94 s at 448 nm, 17.03% and 1.11 s at 686 nm, respectively. An electrochromic device (ECD) based on PTEPA and poly(3,4-ethylenedioxythiophene) (PEDOT) was also constructed and characterized. This ECD was found to have a neutral green state, good switching times, reasonable contrast, satisfactory optical memories and redox stability.