Novel flexible photochromic device with unprecedented fast-bleaching kinetic via platinum decoration on WO3 layer

Abstract

Photochromic devices (PC) are considered as ideal candidates for integrated building applications because of their ability to control light and heat transfer into/out of building inner spaces without any external power supply. However, several issues restrict their practical application, including long-term stability concerns due to the volatile nature of the commonly used liquid electrolyte, the high replacement/installation cost associated with their rigid device architecture, and an extremely slow bleaching speed during reversion to their original state due to the lack of an external stimulus such as electricity. The present study aimed to resolve these bottlenecks. Firstly, we exploited a highly stable and conductive polymer-gel electrolyte based on UV-curable trivalent acrylate instead of using organic liquid-based electrolytes. Secondly, we explored a low-temperature UV-curing procedure to deposit the chromogenic WO3 and TiO2 layers, suitable for fabricating a flexible PC device. Finally, a catalytic amount of Pt nanoparticles was successfully incorporated on the surface of the WO3 layer using an identical UV-curing route, which was found to significantly enhances the bleaching speed of the resulting PC device. Thanks to the combined positive effects, the fabricated PC device displayed a deep contrast in coloration (approximately 60 %), unprecedented bleaching kinetic with 90 % recovery of its original transmittance value within 45 min in the dark condition, and prolonged long-term operation for over 1000 coloration-bleaching cycles. These results open way to making efficient PCs for not only smart windows but also for other bendable or wearable applications.