Mass-producible slit coating for large-area electrochromic devices

The recent trend of some countries opting to ban the sale of new gasoline and diesel vehicles has led to an increase in the use of electric vehicles and automated driving. In an automobile, windows are the largest source of heat energy between the interior and exterior of the vehicle. By modulating the window material, we can precisely control the amount of heat from sunlight that is allowed to enter the car, reduce the load on heating and cooling. Thus, suppress the energy loss associated with air conditioning by introducing technology to control heat energy in windows, which can also help reduce electricity costs. To this end, our research group has been developing complementary electrochromic devices (ECDs) using Prussian blue and tungsten oxide, which consist of nanoparticles dispersed in aqueous solvents to make inks. Spin coating is used for film deposition at the laboratory level; however, it has a major limitation in terms of uniformity. Therefore, in this study, we fabricated functional thin films by using these inks with slit coating, which is a commercial process. The results obtained confirm that slit coating can be used to deposit approximately 1-μm-thick films as fast as within 20 s and even on large G2 size substrates; further, the uniformity of the films measured based on chromaticity and haze is high. In addition, this effect improves the response time of the ECD. As a future direction, this can be applied to flexible ECD, etc.