Colorless to black electrochromic devices using subtractive color mixing of two electrochromes: A conjugated polymer with a small organic molecule

Herein, we present a facile method for color-tuning an electrochromic device that switched between two neutral colors through simple color mixing of a conjugated polymer, poly(2,2-dimethyl-3,4-propylenedioxythiophene) and an electrochromic small molecule aromatic diester, diethyl-4,4′-biphenyldicarboxylate. The resulting device had a photopic contrast of ca. 57% across the visible spectrum. In addition, the device exhibited color uniformity and stability over 2,000 switches. Using these mixed coloring materials, a large area electrochromic device of 140 cm2 was fabricated, exceeding the size of ophthalmic lenses and small displays.