High performance black-to-transmissive electrochromic device with panchromatic absorption based on TiO2-supported viologen and triphenylamine derivatives

• A novel black-to-transmissive electrochromic device bearing viologen and triphenylamine derivatives was achieved.
• Absorption-complementary viologen and triplenylamine derivatives were designed and synthesized.
• Device combining the two materials realized panchromatic absorption over entire visible region.
• Device exhibited high optical contrast and excellent stability.

A novel black-to-transmissive electrochromic device based on TiO2-supported viologen and triphenylamine derivatives was designed and constructed via the absorption-complementary approach. In the device, cathodically coloring electrochromic material 1,4-bis[((N-phosphono-2-ethyl)-4,4′-bipyridinium)-methyl]-benzene tetrachloride acted as working electrode and novel anodically coloring electrochromic material (4-((4-(dimethylamino)-phenyl)(4-methoxyphenyl)-amino)-benzyl) phosphonic acid acted as counter electrode. The assembled electrochromic device achieved panchromatic absorption over entire visible spectrum with almost zero transmittance in colored state. The optical contrast (ΔT) of the device realized in this work was comparable to the highest value (60%) among all reported black-to-transmissive ECDs. Furthermore, excellent cycling stability was achieved, which maintained almost 80% of the initial ΔT value at 570 nm after continuous 100,000 switchings. These outstanding comprehensive electrochromic performances potentially make this device a promising candidate for electrochromic device applications.

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