Flexible Molecular Electrochromic Devices Run by Low‐Cost Commercial Cells

Abstract The present era has seen tremendous demands for low‐cost electrochromic materials for visible‐region multicolor display technology, paper‐based, flexible, and wearable electronic devices, smart windows, and optoelectronic applications. Towards this goal, the authors report large‐scale, high‐yield and robust polyelectrochromic devices fabricated on rigid to flexible ITO substrates comprising novel anthracene containing viologen, (1,1″‐bis(anthracen‐9‐ylmethyl)‐[4,4″‐bipyridine]‐1,1'‐diium bromide, abbreviated as AnV²⁺), and polythiophene (P3HT). Interestingly, the devices show three states of reversible visible color in response to the applied bias, sub‐second to second switching time (0.7 s/1.6 s), high coloration efficiency (484 cm²/C), and longer cycling stability up to 9,000 s (3,000 switching cycles). Introduction of the anthracene moieties to viologen inhibits the formation of an undesired dimer of cation radicals in response to the applied bias, otherwise the device's color‐switching would be hampered when the bias polarity is reversed. The fabricated electrochromic devices are tested with commercially available low‐cost cells to perform—a unique approach toward practical applications. The computational study facilitates the understanding of experimental results. Alternating current (AC)‐based electrical impedance spectroscopy reveals that P3HT facilitates enhanced charge transfer to AnV²⁺. This work shows CMOS compatibility and can pave the way for developing cost‐effective flexible and wearable electrochromic devices.