Structure evolution of electrochromic devices from ‘face-to-face’ to ‘shoulder-by-shoulder’†
A traditional electrochromic device contains at least five functional layers; the electrochromic film exactly faces the counter electrode and matches it in size and color. This face-to-face structure is cumbersome for device flexibility and integration; thus, it is difficult for these devices to meet sophisticated application needs. Concurrently, a lateral electrochromic structure in which the electrochromic film and the counter electrode are arranged in a shoulder-by-shoulder manner was proved to be a superior choice for many specific applications. However, systematic exploration of the shoulder-by-shoulder EC structure is lacking. Herein, a WO3 vs. WO3 electrochromic system was constructed to systematically discuss the EC characteristics and superior applications of the shoulder-by-shoulder structure. Surprisingly, when one EC unit in the shoulder-by-shoulder system was first colored at a certain transmittance, a much faster response time and a lower driving voltage than those of the traditional face-to-face structure were achieved. Additionally, this configuration endowed the counter electrode with great freedom in terms of material, shape and placement position, and it showed great superiority in vast applications. These results provide insight into the structure evolution of electrochromic devices.