Unlocking the Full Spectrum: A Paradigm Shift in Electrochromic Devices with High-Performance Black Conjugated Polymers

Abstract

Abstract The black-to-transparent electrochromism is hailed as the "Holy Grail" of organic optoelectronics. However, designing black electrochromic (EC) materials that fully absorb in the visible light region remains challenging. Electroactive materials that simultaneously possess excellent cyclic stability, fast switching times, and high coloration efficiency are extremely rare. In this work, copolymers capable of fully absorbing across the entire visible spectrum have been successfully designed through judicious selection of four types of monomers. We introduce two types of polar side chains, which synergistically improve the ionic conductivity of copolymer, thereby enhancing the performance of electrochromic devices(ECDs). ECDs exhibit unprecedentedlong-term cyclic stability, surpassing all previously reported high cyclic stability devices with over 126,786 cycles. Additionally, they achieve a coloration efficiency of 1273 cm²/C, which exceeds that of every high coloration efficiency ECDs present so far, along with fast coloring/bleaching times of 0.82 s/0.86 s. This study presents a new strategy for the design and synthesis of high-performance black electrochromic copolymers.