Lightweight, highly bendable and foldable electrochromic films based on all-solution-processed bilayer nanowire networks

Abstract

Mechanical and electrochemical stability issues of electrode materials have been long-standing obstacles restricting the development of highly flexible electrochromics. Herein, a lightweight, highly bendable and foldable electrochromic (EC) film is realized through the construction of mechanically and electrochemically stable bilayer nanowire networks (BNNs) on ultra-thin polyethylene terephthalate (PET) substrates. These BNNs composed of silver nanowires (AgNWs) and W₁₈O₄₉ nanowires (W₁₈O₄₉NWs) are prepared using a facile and continuous spray-coating method. An alginic acid/poly(dopamine) complex (Aa–PDA) and a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer are used as a binder and a charge balancing layer, respectively, to enhance the interfacial and structural stability of nanowires and prevent the electrochemical corrosion of AgNWs. These optimized and highly flexible EC films exhibit good optical contrast, high coloration efficiency (up to 118.1 cm² C⁻¹), highly enhanced electrochemical stability and excellent structural stability even after 500 bending or 100 folding cycles. Moreover, EC films per square centimeter weigh less than 2.3 mg. The spray-coating method is easily controlled and allowed for convenient patterning, which is important for real-life applications.