Electrochromic/Electrofluorochromic Devices based on Terpyridine‐Attached Viologen Derivatives

Abstract 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.