From Traditional to Novel Printed Electrochromic Devices: Material, Structure and Device

Effect of metal dopants on the electrochromic performance of hydrothermally-prepared tungsten oxide materials

Electrochromic (EC) glass has the potential to significantly improve energy efficiency in buildings by controlling the amount of light and heat that the building exchanges with its exterior. However, the development of EC materials is still hindered by key challenges such as slow switching time, low coloration efficiency, short cycling lifetime, and material degradation. Metal doping is a promising technique to enhance the performance of metal oxide-based EC materials, where adding a small amount of metal into the host material can lead to lattice distortion, a variation of oxygen vacancies, and a shorter ion transfer path during the insertion and de-insertion process. In this study, we investigated the effects of niobium, gadolinium, and erbium doping on tungsten oxide using a single-step solvothermal technique. Our results demonstrate that both insertion and de-insertion current density of a doped sample can be significantly enhanced by metal elements, with an improvement of about 5, 4 and 3.5 times for niobium, gadolinium and erbium doped tungsten oxide, respectively compared to a pure tungsten oxide sample. Moreover, the colouration efficiency increased by 16, 9 and 24% when doping with niobium, gadolinium and erbium, respectively. These findings suggest that metal doping is a promising technique for improving the performance of EC materials and can pave the way for the development of more efficient EC glass for building applications.

High-Performance and Stability Electrochromic Devices with a Water Isotopologue

In this report, an ammonium metatungstate (AMT) and ferrous chloride [Fe(II)Cl2] electrochromic liquid (ECL) was synthesized using a hydrothermal method, with D2O used as the solvent instead of H2O. The results show that the use of D2O can improve the stability and performance of ECLs. The hydrogen evolution process in electrochromic devices (ECDs) filled with ECL becomes more difficult, while the material exchange process becomes easier. The ECD exhibits a color modulation amplitude of 58%@680 nm at 2 V. After 500 cycles, the device's performance remains above 95% at a current density of 1.5 mA/cm2. Hydrogen bonds in D2O solutions are expected to exhibit stronger forces compared to those in regular H2O solutions. Therefore, we hypothesize that enhancing the strength of hydrogen bonds in H2O solutions is an effective approach for improving the performance and stability of electrochromic solutions.