Unprecedented facile approach of multiple amino-substituted triphenylamine derivatives for electrochromic devices with extremely high coloration efficiency and unexpected redox stability

Generally, the amino group is considered highly reactive and unstable. Thus, the amino derivatives would be entirely consumed by polymerization or end-capping to preserve the material stability in most research or application fields. Herein, we demonstrated that triphenylamine (TPA) with multiple para-amino substituents could reduce oxidation potential and provide extra oxidation sites while retaining their reversibility. Four para-amino-substituted TPA derivatives (TPA-1N, TPA-2N, TPA-3N, and TPA-ADM) designed and prepared in this study exhibited excellent stability under the electrochemical redox procedure, revealing more than 88% reversibility in the continuous cyclic voltammetry process up to 10,000 cycles. Among all the electrochromic devices, TPA-3N/HV performs the highest coloration efficiency (631 cm2/C), coloration speed (46.4 % s−1), and superior stability, manifesting a reversibility of 99% or 98% after 1000 cycles (switching) or 10 h (maintaining at coloring state), respectively.