All-Solid-State Proton-Based Tandem Structure Achieving Ultrafast Switching Electrochromic Windows
Abstract All-solid-state electrochromic devices (ECDs) for smart-window applications currently suffer from limited ion diffusion speed, which lead to slow coloration and bleaching processes. Here, we design an all-solid-state tandem structure with protons as diffusing species achieving an ultrafast switching ECD. We use WO3 as the electrochromic material, while poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) as the solid-state proton source to enable fast switching. This structure by itself exhibits low optical modulation (i.e., difference of on/off transmittance). We further introduce a solid polymeric electrolyte layer on top of PEDOT:PSS to form a tandem structure, which provides Na+ ions to PEDOT:PSS and pump protons there to the WO3 layer through ion exchange. Our new all-solid-state ECD features high optical modulation (>92% at 650 nm), fast response (coloration to 90% in 0.7 s and bleaching to 65% in 0.9 s and 90% in 7.1 s) and excellent stability (<10% degradation after 3000 cycles). Large-area (30×40 cm2) as well as flexible devices are fabricated to demonstrate the great potential for scaling up.
