Targeted enhancement of electrochromic memory in Fe(II) based metallo-supramolecular polymer using molybdenum disulfide quantum dots

Bistable electrochromic (EC) display with long EC memory has been a much-anticipated goal owing to its zero-energy consumption when maintaining the colored or bleached state when used in smart windows. However, it is very challenging to engineer the structure of the materials to accomplish a long EC memory along with high optical contrast, durability, switching fastness, and coloration efficiency which are of significance for fabricating the electrochromic devices with essentially power efficiency. Herein, we have judiciously incorporated the charge trapping MoS 2 quantum dots (QDs) to prepare an electrochromic nanocomposite (polyFe-QD-10) of an Fe 2+ -based metallo-supramolecular EC polymer (polyFe) for the targeted enhancement of EC memory than the pristine polyFe polymer. The polyFe-QD-10 based electrochromic device (ECD) exhibits more cycle durability as it produced no loss in ΔT after the measurement of 100 cycle, while pristine polyFe-based ECD produced 14% loss in similar 100 cycle. The prototype ECD with polyFe-QD-10 film is also demonstrated with fast switching time (3.3 s for bleaching and 0.78 s for coloring), and good coloration efficiency (242.2 cm 2 C −1 ). Remarkably, the ECD based on polyFe-QD-10 composite displays higher EC memory in open circuit condition as it takes 32 min for 90% reappearance of the original purple color after complete bleaching, while the pristine polyFe based ECD regains 90% of the transmittance of the color state only in 15 min. The strategy reported here presents the polyFe-MoS 2 QD composite thin film an encouraging candidate for developing power efficient electrochromic information displays and smart windows. • MoS 2 quantum dots (QDs) enhance the electrochromic (EC) memory of Fe-based polymer. • Charge trapping property of MoS 2 QD improves the EC memory of nanocomposite device. • The solid-state device shows fast and durable electrochromism with high coloration efficiency. • A facile and robust strategy to enhance electrochromic memory as well as power efficiency.