Inkjet Printing of Sol–Gel Synthesized Hydrated Tungsten Oxide Nanoparticles for Flexible Electrochromic Devices

Abstract

Tungsten oxide nanoparticles were synthesized via a sol-gel route using metallic tungsten as precursor, and were printed on a flexible electrode using inkjet printing in order to build solid-state electrochromic cells. Several spectroscopic techniques were used to characterize and compare tungsten oxide particles obtained from different origins. FTIR, Raman and X-ray diffraction spectroscopic measurements showed that the sol-gel synthesis described here produces nanoparticles mainly in an amorphous state with hexagonal crystalline domains and allowed the analysis of the hydration extent of those nanoparticles. The size was measured combining dynamic light scattering, sedimentation, and microscopic techniques (AFM), showing a consistent size of about 200 nm. The tungsten oxide nanoparticles were used to produce an ink formulation for application in inkjet printing. Solid-state electrochromic devices were assembled at room temperature, without sintering the tungsten oxide printed films, showing excellent contrast between on/off states. Electrochemical characterization of those films is described using cyclic voltammetry. The devices were then tested through spectroelectrochemistry by Visible/NIR absorption spectroscopy (400-2200 nm range), showing a dual spectroscopic response depending on the applied voltage. This phenomenon is attributed to the presence of two different crystalline states in accordance with results obtained from the spectroscopic characterization of the nanoparticles. The electrochromic cells had a good cycling stability showing high reversibility and a cyclability up to more than 50,000 cycles with a degradation of 25%.

Layer-by-Layer Assembly of PEDOT:PSS and WO3 Nanoparticles: Enhanced Electrochromic Coloration Efficiency and Mechanism Studies by Scanning Electrochemical Microscopy

“…The WO 3 NPs were prepared via hyrdrothermal process from metallic W powder, which could be dispersed in water without any additives [26,27]. The electrochromic thin films were obtained by LBL self-assembly.…”

Electrochromic thin films of sodium intercalated vanadium(V) oxide xerogels: Chemical bath deposition and characterization

“…The synthetic procedures at ambient conditions usually produce hydrated vanadium(V) oxides, V 2 O 5 ·nH 2 O, known as xerogels which adopt layered structures with V 2 O 5 layers and interstitial water molecules [1][2][3]. Vanadium(V) oxide xerogels like crystalline V 2 O 5 are typical intercalation compounds with multiple valence state of vanadium which enables redox-dependent properties [4][5][6].…”

Optical properties of hydrated tungsten trioxide 3WO3·H2O

“…There are many crystalline hydrated tungsten trioxide compounds having the general formula nWO 3 H 2 O. Due to the wide application in modern technology, their properties are studied intensively and results have been reported for nWO 3 H 2 O compounds with n = 0.5, 1, 1.25, 2 and 3 [2][3][4][5][6][7][8]. Efficiency of electrochromic (EC) thin-film devices depends on the thicknesses of EC materials [9] as well as on their structure, optical properties and chemical purity.…”