A Solution‐Processible Perylene Diimide Polymer for High‐performance Electrochromism

Abstract Solution‐processable electrochromic materials are promising to fabricate thin film with low manufacturing cost production and allow a variety of applications in smart windows and optical displays. In this work, a positively‐charged tetrachlorinated perylene diimide (PDI‐CHO) with two aldehyde functional groups has been designed as a new building block, to prepare redox‐active polymer PDI‐BTH. Benefiting from the charged backbone, the obtained polymer shows good solubility in polar DMSO solvent, allowing cost‐effective fabrication of high‐quality thin film with controllable thickness by simple drop‐casting method. The obtained film exhibited multi‐electrochromic behavior including red, gray, and blue colors as a result of the two‐step redox process. It Is further demonstrated that this polymer film exhibits fast switching times (1.2 s), remarkably high coloration efficiency (1093 cm ² C ⁻¹ ), great optical contrast (60% at 650 nm), and good cycle stability (90% optical retention over 125 cycles). It is believed that the presented molecular design would also be adaptable to a wide range of aromatic dimides with tunable optoelectronic properties.