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.
Highlights
Nowadays, electrochromism has had applications in many fields such as energysaving smart windows [1,2,3,4,5], batteries [6], sensors [7], next-generation displays and wearable electronics [8]
WO3 electrochromic film was successfully prepared by screen printing
The addition of Polyvinyl alcohol (PVA) improved the dynamic viscosity of the precursor solutions and modify the uniformity of the films
Summary
Electrochromism has had applications in many fields such as energysaving smart windows [1,2,3,4,5], batteries [6], sensors [7], next-generation displays and wearable electronics [8]. Does the raw material have high cost-performance, and WO3 film has excellent electrochromic properties such as high optical contrast and low energy consumption [9]. There are many methods to prepare electrochromic films such as magnetron sputtering [10,11,12], ion plating and sol-gel [13,14,15,16]. There have been studies on the electrochromic film preparation by the hydrothermal method [17,18]. As the mainstream industrial preparation method, magnetron sputtering requires complex equipment and process, which makes it hard to reduce the cost and further industrialize. To solve the cost problem, screen printing and inkjet printing have become the research emphasis of electrochromic film preparation because of their high cost-performance, simple process and low environmental requirements. It is commonly used to prepare film in thermoelectric devices [19,20], flexible transparent electrode [21,22], organic semiconductor device [23]
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