A Propylpyridinyl Triazine Salt for Dual‐Band Electrochromic Devices with Accelerated Response by Sulfonyl Group

Abstract

The chromophore 2,4,6‐tri(pyridyl‐4‐(3‐sulphonatopropyl))‐1,3,5‐triazine (TPST) was used in hydrogel electrochromic devices (ECDs). The hydrogel consists of TPST, K3[Fe(CN)6]/K4[Fe(CN)6] (K3) or 1,1’‐ferrocenedimethanol (FM), and sodium carboxymethyl cellulose. The devices showed dual‐band properties, K3‐TPST exhibiting absorption in NIR region at low voltage, while absorption of ECDs blue‐shifting at −2.8 V. ECDs changed from transparent to olive green to black with a coloration efficiency of >126.74 cm2/C at 850 nm and high cycling stability. The optical contrast of FM‐TPST ECD remains 79.3 % of the first cycle contrast after 2100 cycles. TPST can change its color from transparent to black at a high voltage of −2.2 V, with relatively short switching times (FM‐TPST, 5.3 s, and K3[Fe(CN)6]/K4[Fe(CN)6]‐TPST, 3.8 s). The response was accelerated up to 5 times by introducing a sulfonyl group with comparison to our previous work. The devices using TPST with sulfonyl moiety provide a new way for the fast‐response energy‐saving smart windows.