High performance in electrochromic amorphous WO_x film with long-term stability and tunable switching times via Al/Li-ions intercalation/deintercalation

Lithium ion (Li⁺) aggregation in the amorphous tungsten oxide (a-WO_x) film is the main cause of the electrochromic (EC) device failure. This has hindered a-WO_x films goes towards industrialization on behalf of the giant EC performance and long-term reliability. A novel kind of electrolytes consisted of Aluminum ions (Al³⁺) and Lithium ions (Li⁺) used for electrochromic sputtered a-WO_x films is presented. With the newly designed Al³⁺/Li⁺ co-existed electrolytes, the optical transmittance modulation can be largely enhanced compared with Li⁺, meanwhile, the problem of degradation after long-term cycling for a-WO_x induced by Li ions-trapping is able to be solved. Furthermore, the utilization of Al³⁺ brings slow switching kinetics at the ions extraction step to the films compared with Li⁺, which supplies a new method to modulate the bleaching rate by applying adjustable Al³⁺/Li⁺ ratio of electrolytes and a tunable and controllable switching time is easily achieved in this work. This Al³⁺/Li⁺ co-based electrolyte opens a new way to design and control the high contrast, long-lived cycling stability and changeable switching time EC devices based on a-WO_x films.