Energy saving electrochromic windows were achieved by controlling the interfacial charge transfer using low-HOMO level (EHOMO < −5 eV) π-conjugated polymers (CPs) as bistable electrochromic films and an ionic liquid as the electrolyte layer. It provided a long bistability (>90 min) at the voltage-off state with a high coloration efficiency (879 cm2 C−1).

An electrochemically stable and bistable switchable mirror is achieved for the first time by introducing a thiol-modified ITO electrode to stabilize the metallic film and ionic liquids as an anion-blocking layer, to achieve a long memory effect.

Highly transparent TiO 2 nanoparticles are explored as a non-electrochromic (non-EC) charge-balancing layer for a high color contrast, bistable electrochromic window (ECW). The TiO 2 nanoparticle (TNP) layer increases the potential at the EC polymer electrode, thereby lowering the working voltage of the ECW. This leads to lower the power consumption of ECWs without loss in the high color contrast (ΔT > 72%) and to remarkably improve the cyclability (ΔT change <1% over 3000 cycles), mainly due to the low overvoltage (<0.1 V) on the electrochromic polymer layer. Furthermore, the ECWs including the non-EC TNP layer show long-term bistability (>2.7 h, 40% increase) and UV stability (ΔT change <1%) to provide a low-power automatic ECW. This finding shows that the charge balanced ECP window has the potential to be used for an energy saving ECW with low-power consumption and will be widely applied in various ECWs as well as electrochemical devices with multiple functions.

A fl uorescent naphthalimide-tetrazine dyad (NITZ) was examined for electrofl uorochromism. The reversible electrochemistry of the tetrazine was accompanied by the fl uorescence change through a quasi-complete energy transfer in an electrochemical cell prepared by the mixture of polymer electrolyte and naphthalimide-tetrazine dyad. Owing to the energy transfer within the dyad (naphthalimide and tetrazine), the fl uorescence effi ciency of NITZ was much enhanced and the effective fl uorophore concentration in this system was much less than other tetrazine based electrofl uorochromic device (EFD). Thus the yellow fl uorescence of NITZ was switched on and off remarkably even with small quantity of NITZ (1 wt.%) in an EFD upon application of step potentials for different redox state. Furthermore, multicolor fl uorescence switching was achieved by blending a naphthalimide to the electrofl uorochromic layer, to show white-blue-dark state of fl uorescence. Since the tetrazine and naphthalimide units have their emission quenched at different potentials, the emission color could be tuned by quenching emission at selected wavelengths, reversibly, under low working potentials.for electrofl uorochromic cell opens a new method to control fl uorescence color.

A π-conjugated polymer of propylenedioxythiophene-phenylene (ProDOT-Ph) with a chiral alkyl substituent on the propylene bridge of ProDOT was prepared to explore reversible multiswitching chiral conjugated polymers (CCPs) capable of electrochromic, electrofluorochromic, and chirality switching. The chiral assembly of the yellow colored poly(ProDOT-Ph)s (YPCr) was optimized by annealing the YPCr films at 120 °C. From the thermally annealed YPCr films, we demonstrated the electrical switching of chirality, color, and fluorescence in a single device, for the first time, which was precisely controlled electrochemically to achieve highly efficient and reversible switching of chiral assembly at a low working potential. The YPCr films showed electrochromism with a high coloration efficiency of 690 cm 2 C −1 by changing color between yellow and blue. The film also exhibited fluorescence switching with a quantum yield change from 3.8 to 0.21 during the reversible electrochemical switching. The chirality of the YPCr, which showed a negative bisignate Cotton effect, was switched reversibly with 97% change in the anisotropy factor (g abs ). The multiswitching properties were correlated to the electrochemical switching in chiral assembly of conjugated polymers according to the electrochemical doping/dedoping process. To the best of our knowledge, the change in Cotton effect during the switching is the highest reported value of a chirality tunable polymer without any chiral inducer. In addition, the YPCr showed a sustainable memory effect for both chirality and coloration.