Controllable and large-scale fabrication of flexible ITO-free electrochromic devices by crackle pattern technology

Electrochromic devices (ECDs) presenting reversible color variation are considered as the most promising alternative to traditional smart windows. However, the fabrication of large-scale ECDs with high flexibility and stability is still challenging. In this work, we present a crackle pattern technology for controllable and large-scale fabrication of rectangular Ag network films for indium tin oxide-free (ITO-free) flexible ECDs. This rectangular Ag film exhibits superior mechanical robustness and controllable optoelectronic performance (2.0 Ω sq−1 at 91% transmittance). In the application of WO3 based ECD, the rectangular film presents an ultrafast switching time (0.25/0.18 s for bleaching/coloring) and is thus applicable in flexible displays. Moreover, this device demonstrates a large optical modulation of 76% at 630 nm and sustains 78.9% of its initial modulation even after 20 000 cycles, which is close to the commercial standard for rigid ECDs. The obtained rectangular Ag films are successfully assembled into a flexible all-solid-state ECD (21 × 13 cm2), which can be utilized in smart windows, glasses and other fields that require bending or cutting.