UV-blocking luminescent hybrid electrolyte doped with [BMIm][Trif], lithium salt and carbon dots derived from Arundo donax leaves for electrochromic windows

• A flexible solid-state electrolyte based on di-ureasil xerogel was developed and doped with 1-butyl-3-methylimidazolium, lithium trifluoromethanesulfonate and Arundo donax leaf-derived carbon dots. • Structural and spectroscopic analyses confirmed successful dopant incorporation and revealed reorganization of hydrogen bonding networks toward more ordered aggregates. • CDs enhanced excitation-dependent photoluminescence, reaching a maximum quantum yield of 8%, with suppressed aggregation-induced quenching in the solid matrix. • Electrochromic device (ITO/WO₃/electrolyte/NiO/ITO) showed high-performance electrochromism and long-term stability: high contrast (ΔT = 37%), stable optical density (ΔOD ≈ 0.33), and improved coloration efficiency after 50 cycles. In this work, we propose novel electrolytes based on a low molecular weight poly(oxypropylene) (POP)/siloxane di-ureasil matrix (d-U’(400)) doped with lithium triflate (LiTrif), and/or the ionic liquid (IL) 1-butyl-3-methylimidazolium triflate ([BMIm]Trif), and/or carbon dots (CDs) derived from Arundo donax leaves. This multifunctional electrolyte was successfully incorporated in an integrated electrochromic device (ECD)/thermotropic device (TTD) system aiming for applications in smart windows for energy-efficient buildings. While the presence of the dopants did not compromise the amorphous nature and texture features of d-U’(400), it promoted a significant reorganization of the hydrogen bonded network. Specifically, a reduction in disordered urea/POP aggregates and an enhancement of more ordered urea/urea ordered aggregates were observed, an effect that was particularly pronounced upon introduction of the CDs and LiTrif. The resulting electrolytes demonstrated excitation-dependent photoluminescence properties similar to those of d-U’(400), with CDs showing reduced aggregation-induced quenching. The maximum photoluminescence absolute quantum yield (8 ± 1 %) was found for d-U’(400)-CD-IL-Li. The ECD component of the ECD/TTD system was tested. The electrochromic performance of the integrated ECD/TTD system was evaluated using a glass/ITO/a-WO₃/d-U’(400)-CD-IL-Li/c-NiO/ITO architecture (where ITO is indium tin oxide, a-WO 3 is amorphous tungsten oxide, and c-NiO is polycrystalline nickel oxide). The device demonstrated attractive performance: high switching efficiency (transmittance (T) variations of 36/21% at 550/1200 nm), high optical density modulation (0.33/0.38 at 550/1200 nm). High coloration efficiency was achieved at the 50 th cycle (−618.87/−713.01 cm 2 C −1 and +381.14/+439.12 cm 2 C −1 at 550/1200 nm for coloration and bleaching, respectively), together with remarkable electrochemical stability. The ECD offers two voltage-actuated modes: bright warm (+4.0 V, T = 68/36% at 550/1200 nm) and semi-bright cold (−3.0 V, T = 7/11% at 550/1200 nm). Overall, this work contributes to current efforts toward next-generation ECD by combining an organic–inorganic electrolyte with multifunctional additives, in line with recent advances and emerging design strategies for efficient, stable, and application-oriented electrochromic systems.