“Colorless to other colors” electrochromic polymer materials: structural design strategies and current development status

Abstract

Electrochromic materials have attracted extensive attention due to their ability to achieve rapid and reversible regulation of optical properties under low-voltage driving. Endowed with advantages such as high energy conversion efficiency, low energy consumption, and excellent functional expandability, they have been successfully applied in intelligent fields including architectural smart windows, electric vehicles, and space shuttles. Among them, polymer-based electrochromic materials have become a key research and development focus because of their rich color-changing varieties, fast color switching, and feasibility of roll-to-roll processing. According to their color-changing characteristics, polymer-based electrochromic materials are mainly classified into two categories: “colored to other colors (including colorless)” and “colorless to other colors”. These two types of materials not only show distinct contrasts in color-changing features but also form a perfect complementary relationship in practical applications. The “colorless to other colors” electrochromic polymers, as new types of materials that have developed rapidly in the past 20 years, possess significant scientific research interest and practical application value. However, up to now, there has been a lack of detailed analysis and reports on the design, development, and research progress of such materials. Therefore, this review will sort out and introduce the development status of these materials from the perspective of the structure–property relationship between material structure and electrochromic characteristics, summarize the strategies for designing and developing such polymer materials, and discuss the future development trends of these materials.