Electrochromic devices incorporating biohybrid electrolytes doped with a lithium salt, an ionic liquid or a mixture of both

The sol-gel method was employed in the synthesis of di-urethane cross-linked poly(ϵ-caprolactone) (PCL(530))/siloxane biohybrid ormolytes incorporating either a mixture of lithium triflate (LiCF₃SO₃) and the ionic liquid (IL) 1-ethyl-3-methyl imidazolium tetrafluoroborate ([Emim]BF₄), or solely with [Emim]BF₄ or LiCF₃SO₃. The ormolyte doped with [Emim]BF₄ is thermally more stable and exhibits higher ionic conductivity (4 × 10⁻⁴ and 2 × 10⁻³ S cm⁻¹ at 36 and 98 °C, respectively) than those containing the LiCF₃SO₃/[Emim]BF₄ mixture or just LiCF₃SO₃. The three ormolytes were employed in the production of glass/ITO/ormolyte/WO₃/ITO/glass electrochromic devices (ECDs) designated as ECD@Y with Y = Li-[Emim]BF₄, [Emim]BF₄ and Li. The three ECDs displayed fast switching speed (ca. 30 s). ECD@Li-[Emim]BF₄ exhibited an electrochromic contrast of 18.4% and an optical density change of 0.11 in the visible region, the coloration efficiency attained at 555 nm was 152 and 80.2 cm²C⁻¹ in the “on” and “off” states, respectively, and the open circuit memory was 48 hours. In the “on” state the CIE 1931 color space coordinates were x = 0.29 and y = 0.30, corresponding to blue color.