Molecular engineering of colorless triphenylamine-based polymers for multicolor electrochromism and energy storage

Four V-shaped monomers (MMTPA, MFTPA, FMTPA, FFTPA) consisting of two triphenylamine units located on the 4,5-positions of the imidazole-based π-spacers were prepared by one-pot condensation reaction, and further deposited on ITO substrates by electrochemical polymerizations for electrochromism and energy storage. The present polymers (PMMTPA, PMFTPA, PFMTPA, PFFTPA) exhibited efficient multicolor colorless-to-orange-to-blue electrochromism, involving large optical contrast over 60 %, short response time less than 3 s, high coloration efficiency over 190 mC·cm−2, as well as good switching stability. Additionally, all these triphenylamine-based polymer thin films exhibited high area ratio capacitance over 6 mF cm−2 at the current density of 0.1 mA cm−2. The electrochromic energy storage devices based on these polymers were fabricated and could light the LED bulb with visualizing the energy storage state, which guaranteed their potential applications in energy saving smart windows.