Fast Switching Triphenylamine-Based Electrochromic Polymers with Fluorene Core: Electrochemical Synthesis and Optoelectronic Properties

Most of the triarylamine-based electrochromic polymers are achieved through arylamine-based oxidative coupling reactions where the electrochromic properties of the polymer could only be realized after fabrication of the film on optically transparent electrodes. Electrochemical polymerization, on the other hand, is an in situ polymerization method which offers synthesis of the polymer and fabrication of the films on the electrode surface simultaneously. In this study two new triphenylamine monomers (TPAFLA and TPAFLS) having fluorene core were synthesized and successfully electrochemically polymerized. The electrogenerated polymer films exhibited strong color changes (P(TPAFLA):yellow, orange, green, deep blue, P(TPAFLS): pale yellow, pale blue) and rapid switching responses (P(TPAFLA):1.61 s at 362 nm, P(TPAFLS):0.69 s at 390 nm) and high coloration efficiency (P(TPAFLA):114 cm²C⁻¹, P(TPAFLS):192 cm²C⁻¹) compared to other triphenylamine derivatives. Furthermore, electrochemical copolymerization of TPAFLA with 3,4-ethylenedioxythiophene (EDOT) was successfully achieved for the first time and the copolymer revealed significantly lowered band gap with remarkably enlarged color palette (violet, yellow, green, light blue and blue).