Implementation of high-performance electrochromic device based on all-solution-fabricated Prussian blue and tungsten trioxide thin film

Electrochromic devices (ECDs) rely on interfacial charge-transfer and ion transport. They generally suffer from a decline in their operational performance, which is caused by irreversible redox reactions, ion accumulation, or overpotential at the solution/electrode interface. Herein, we implement high-performance ECDs with excellent optical modulation (45.9%), fast switching speed (3 s), high coloring efficiency (98.1 cm(2)/C), and excellent long-term performance (>1000 cycles) under the bias of 0.7 V through in-depth optimization of device components and modulation of its driving characteristics. Three requirements for device structure and operation were considered to implement high-performance ECDs; i) uniformity and robustness of the electrochromic (EC) film in the working electrode (WE), ii) high surface area and fast redox properties of the complementary electrode, iii) total offsetting of the charge applied in the device during the coloring/bleaching process. Various electrodeposition methods such as galvanostatic, potentiostatic, pulsed potential, and triple pulse potential application were exploited to fabricate the active layers, and the active layers produced under optimized conditions through individual studies on the most stable film stability, electrochemical behavior, EC and ion storage characteristics were assembled in the devices. Under all optimized conditions, we constructed high-performance ECDs composed of electrodeposited Prussian blue (PB) as an EC layer and tungsten trioxide (WO3) as a complementary layer, respectively. In particular, the offset of the charge applied to the device between the coloring and bleaching processes drastically improved the long-term stability of EC performance under low operating bias. The results provide a useful basis for enhancing the performance of ECDs and can be widely applied to various ECDs. (c) 2020 Elsevier Ltd. All rights reserved.