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

Graphical Smart windows : The sulfonyl group-bearing 2,4,6-tri(pyridyl-4-(3-sulphonatopropyl))-1,3,5-triazine (TPST) together with K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] or 1,1′-ferrocenedimethanol exhibits fast dual-band electrochromic performance, which is useful for electrochromic intelligent dynamic window. 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, K 3 [Fe(CN) 6 ]/K 4 [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 cm 2 /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 K 3 [Fe(CN) 6 ]/K 4 [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.