부산대학교 도서관

Viologen-based electrochromic materials have been frequently reported, with a wide visible range of reversible colors. According to the theory of subtractive color mixing, achromatic black color can be produced by blending the primary chromatic components in proper proportions. However, a single-component black viologen is still rare due to the limited conjugation length required for entire visible light absorption. In this study, we have synthesized an asymmetric viologen that produces a true black color. Furthermore, to fabricate electrochromic fabric devices (ECFDs), the layer-by-layer structure is applied to a polyester fabric substrate, and the conductive electrode is prepared by spray-coating silver nanowire and PEDOT:PSS. The ECFDs exhibit outstanding absorption behaviors with green-to-black gradient color switchings, extending into the near-infrared region. Superb electrochromic behaviors include a low voltage requirement of -2 V, a significant optical contrast of 54.1% at 608 nm, a high coloration efficiency of 192.8 cm2/C, and long-term switching stability for up to 4,000 seconds, with switching times of less than 20 seconds. Additionally, these ECFDs are durable when bent and are resistant to water. Furthermore, the exceptional heat-absorption capability of the resulting black ECFDs is also assessed. The findings illustrate the successful development and potential of color-changing fabric devices, opening up efficient heat-absorbing e-textile applications.