High-performance all-solid-state electrochromic devices driven by ultrafast H+ transfer

As an energy-efficient technology, electrochromic devices (ECDs) represent a promising solution for smart windows in buildings and vehicles. However, conventional all-solid-state ECDs suffer from sluggish ion diffusion. Here, we propose a high-performance all-solid-state ECD enabled by a rapid H + transfer pathway. A solid-state polyaniline (PANI) interface serves as an efficient H + reservoir, replacing Li + ions to drive electrochromism in Prussian blue (PB). By integrating a sodium-ion-conducting solid polymer electrolyte (SPE) above PANI, H + ions are selectively pumped into PB via an ion exchange mechanism. The PANI network also stabilizes PB's framework by preventing anion/solvent intercalation. The optimized ECDs exhibit exceptional performance: fast switching speeds (1.2 s coloration, 3.0 s bleaching), high optical modulation (72.5% at 600 nm), and robust cycling stability (>5,000 cycles with <10% decay). Furthermore, large-area flexible ECDs (20 × 30 cm 2 , ∼0.4 mm thickness) are demonstrated, highlighting their potential as replaceable smart films for energy-efficient buildings and vehicles.