Modifying Precursor Solutions to Obtain Screen-Printable Inks for Tungsten Oxides Electrochromic Film Preparation

Abstract

Tungsten trioxide (WO3) is used to prepare the important electrochromic layer of the electrochromic device as a wide bandgap semiconductor material. In this study, WO3 electrochromic film was successfully prepared by screen printing. To modify the thixotropy and wettability of the ink, polyvinyl alcohol (PVA) and 2-perfluoroalkyl ethanol (FSO) were added in the ammonium meta-tungstate (AMT) solution. We found that the PVA additive could improve the dynamic viscosity of the solution and modify the uniformity of the film. 2-Perfluoroalkyl ethanol (FSO) could lower the surface tension and increase the wettability of the AMT solution on the substrate. By observing the morphology of the printed films, the ink formulas for screen printing were selected. We found the annealing process could help remove PVA. Through characterization of electrochromic performance, it was found that the best performing device had 42.57% modulation and 93.25 cm2·C−1 coloration efficiency (CE) for 600 nm light. This study showed great potential in the preparation of WO3 electrochromic devices by a low-cost screen-printing method.