Structure and Morphologic Influence of WO₃ Nanoparticles on the Electrochromic Performance of Dual‐Phase a‐WO₃/WO₃ Inkjet Printed Films

Abstract

The optimization of tungsten trioxide (WO3) nanoparticles produced via hydrothermal synthesis for application in electrochromic (EC) devices is reported. The structure and morphology of the nanoparticles are controlled by changing the acidity of the aqueous solvent added to the sol‐gel precursor (peroxopolytungstic acid) during synthesis. Orthorhombic hydrated WO3 nanorods or monoclinic WO3 nanoslabs are obtained when HCl is added, while synthesis only in aqueous medium results in a mixture of both types of polymorphs. Dual‐phase thin films are processed by inkjet printing deposition of the nanoparticles in flexible polyethylene terephthalate substrate with indium tin oxide coating (ITO PET) followed by the deposition of the precursor solution. When compared with purely amorphous tungsten oxide films, the dual phase ones present higher optical densities and improved capacity, and cyclability stability. The best results, obtained for orthorhombic hydrated nanoparticles (ortho‐WO3·0.33H2O), are due to its high surface area and improved conductivity. Additionally, the ex situ X‐ray diffraction (XRD) lithiation studies show evidence of a higher distortion of the monoclinic when compared with the orthorhombic crystallographic structure, which contribute to the inferior EC performance. These results validate the use of inkjet printing deposition with low processing temperatures for EC dual‐phase thin films containing optimized nanoparticles which are compatible with low‐cost substrates.

Simplified All‐Solid‐State WO3 Based Electrochromic Devices on Single Substrate: Toward Large Area, Low Voltage, High Contrast, and Fast Switching Dynamics

“…[35][36][37] Recent reports of Azam et al, [35] showed for EC device based on 2D WO 3 nanosheets an optical modulation of 62.57% during +3 V (bleached state) and −3 V (colored state) and a color-switching response-time of 6.97 s for bleaching and 10.74 s for coloration, whereas Huo et al, [36] observed for devices based on hexagonal/amorphous WO 3 core/shell nanorod arrays an optical modulation of 67.7%, and response times of 15 s for coloring and 21 s for bleaching (±3 V), outperforming performances of ECDs based on pure hexagonal WO 3 nanorods. [35][36][37] Recent reports of Azam et al, [35] showed for EC device based on 2D WO 3 nanosheets an optical modulation of 62.57% during +3 V (bleached state) and −3 V (colored state) and a color-switching response-time of 6.97 s for bleaching and 10.74 s for coloration, whereas Huo et al, [36] observed for devices based on hexagonal/amorphous WO 3 core/shell nanorod arrays an optical modulation of 67.7%, and response times of 15 s for coloring and 21 s for bleaching (±3 V), outperforming performances of ECDs based on pure hexagonal WO 3 nanorods.…”

Disentangling the intricate atomic short-range order and electronic properties in amorphous transition metal oxides

“…However, due to the difficulty in determining local disorder, there is still no well-established electronic localization mechanisms for aTMOs. Unveiling atomic short-range order is thus crucial to understand optical and electronic processes in aTMOs and would also be of vital importance in nanoparticle systems where the high-surface-to-bulk ratio results in lower crystallinity arising from structural reconstruction and surface disorder 8, 9 .…”

Synthesis and Electrochromic Characterization of Graphene/V2O5/MoO3Nanocomposite Films

“…Furthermore, we evaluated the stability of the films by the capacity loss, which was calculated the charge densities difference between the first CV cycle and the following cycles. 34 And the charge densities were the summation of Qc and Qa. As shown in Figure 5, the capacity of GVM film and VM film decrease slightly compared with GV film and V film, respectively, which leads to a better cyclic stability of these films.…”