Enhancing Viologen's Electrochromism by Incorporating Thiophene: A Step Toward All-Organic Flexible Device

An all-organic electrochromic device seems to be a possibility with ethyl viologen (EV) and poly-3-hexylthiophene (P3HT), both being organic materials, showing complementary electrochromic pair for color switching. The EV-P3HT layer, sandwiched between ITO-coated glass substrates shows switching between maroon and blue with an applied bias of 1.4 V. Mechanism of the color switching has been examined using UV-Vis and Raman spectroscopies. The fabricated device shows optical modulation of 80%, switching time of 1 s while maintaining cycle life for a period of more than 600 s. The paradigm reported here inches toward realizing a flexible all-organic electrochromic device.