Electrochromic/Electrofluorochromic Devices based on Terpyridine-Attached Viologen Derivatives

Electrochromic/electrofluorochromic (EC/EFC) dual-functional materials with electrochemically switchable colors and fluorescence offer the possibility of developing reflection/emission dual-mode integrated displays in one device. However, unlike the easily adjustable multi-color EC properties, the EFC properties with tunable fluorescence intensity are relatively broad, while those with tunable color emission are rare. Herein, two terpyridine-attached viologen derivatives Tpy-Vio-1 and Tpy-Vio-2 are designed and synthesized for exploring the relationship between molecular structure and their EC/EFC properties. Due to the introduction of 4 '-phenyl-2,2 ':6 ',2 ''-terpyridine groups, Tpy-Vio-1 and Tpy-Vio-2 devices exhibited EFC characteristics in addition to EC properties. Tpy-Vio-1 and Tpy-Vio-2 devices displayed similar color and fluorescence changes after applying electric potentials. Nevertheless, compared to the Tpy-Vio-2 devices, the Tpy-Vio-1 devices possessed lower applied voltage (1.8 V), shorter response times (9.5 s for coloring and 8.5 s for bleaching), higher cyclic stability (480 cycles), and better coloration efficiency (95 cm2 C-1). This study believes that this work will provide effective guidance for the design and preparation of EC/EFC dual-functional materials. Two terpyridine-attached viologens Tpy-Vio-1 and Tpy-Vio-2 are synthesized for EC/EFC devices. Wherein, Tpy-Vio-1-based EC/EFC devices displayed the lower applied voltage of -1.8 V, shorter coloring time of 9.5 s, shorter bleaching time of 8.5 s, better cycling stability of 480 cycles, and higher coloration efficiency of 95 cm2 C-1, which will provide effective guidance for the development of EC/EFC materials. image