Ultraflexible, stretchable and fast-switching electrochromic devices with enhanced cycling stability

Ultraflexible electronics have received extensive attention due to their favorable properties, such as superior mechanical robustness, light weight and good compatibility with large-area roll-to-roll fabrication. Here we present a flexible sandwiched tungsten trioxide/silver nanotrough network/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) multi-layer transparent conducting electrode with prominent conductivity (sheet resistance as low as 1.08 Ω sq^-1) and transparency (85%). In particular, the flexible transparent electrode exhibits excellent mechanical robustness upon bending and stretching. This hybrid electrode can be further adhered tightly to a layer of WO₃ to form an electrochromic device, which simultaneously displays a rapid switching time (0.75 s/1.82 s for bleaching/coloring) and high cyclic performance (86% retention of the initial optical contrast after cycling for 30 000 s). In addition, our electrode can also be fabricated on various flexible substrates, such as polyethylene cling wrap, polydimethylsiloxane and Ecoflex, with sustained electrochromic properties after bending, twisting, stretching and even strong kneading. Our work provides new opportunities for the next generation of flexible and wearable electronics applied on various flexible substrates.