A pH and voltage dual-adjustment of electrochromic material achieves multicolor change based on alizarin red and Dawson-type polyoxometalate

Abstract

A multicolor electrochromic material based on polyoxometalate and a dye with pH and voltage dual-adjustment was studied. The material (PEI/[PEI/P₂W₁₈/PEI/AR]₃₀/PEI (P₂W₁₈-AR) film) was prepared by a simple layer-by-layer method and tested in several solutions of different pH (pH 2.00, pH 4.00, and pH 6.00), referred to as F1, F2, and F3, respectively. By applying different voltages, the color of the film could change from yellow to blue-green (F1), pink-orange to blue-violet (F2), and dark pink to violet (F3), while maintaining good electrochromic performance and stability. Among them, F1 showed the best optical contrast up to 39.71%, and the optical contrast retention rate of F3 was 90.71% after 1000 cycles. Simultaneously, the fabricated electrochromic devices also showed color adjustments. This film was controlled by pH and voltage, providing a new method for the preparation of multicolor electrochromic composite materials.