Conjugated polymer multilayer by in situ electrochemical polymerization for black-to-transmissive eletrochromism

Abstract

A range of novel multilayer films were fabricated onto ITO-coated glass through the multilayer electrochemical polymerization (MEP) technology using three EDOT-based electrochromic polymers (P1, P2 and P3) with additive primary colors red, green and blue (RGB) respectively in the neutral state, and high transmissivity in the oxidized state. As expected, a highly desired black-to-transmissive electrochromic switching with low driving voltages (<1 V) was observed for the resulting multilayer films through straightforward color mixing of polymers P1, P2 and P3. Significantly, the fabricated multilayer films, such as “P1/P2/P3 Multilayer”, possessed the outstanding electrochromic performances, including high optical contrast (exceeding 40%), fast switching speed (coloration time and bleaching time of less than 1.5 s), and lasting cyclic stability (optical contrast retains 89% after 500 steps), which make them hold great potential in practical applications of electrochromic devices, like switchable displays, energy-saving windows, electronic papers and so on. Finally, this work provides a simple and efficient approach towards black-to-transmissive electrochromism, and indicates that it is viable and facile to achieve fine-tuning in colors of electrochromic polymers in virtue of MEP method