Improving the electrochromic properties of the composite films for electrochromic device

Electrochromism is defined as change of the optical property under potential applied. Among the organic electrochromic materials, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is considered as one of the most valuable conductive polymers due to its excellent transmittance in the visible light range, high mechanical flexibility, and easy processing and existing in large quantity as commercial ink. To enhanced the conductivity and the electrochromic properties of the PEDOT:PSS, we recently developed a new method based on the addition of black carbon (BC) leading to PEDOT:PSS + BC composites. Herein, highly conductive and transparent composite thin film–based PEDOT:PSS + BC were facilely fabricated using dip-coating deposition. Thin films made from composite inks exhibit good durability, fast switching time, high transmittance modulations (ΔT ≈ 91% at 550 nm), and high coloration efficiency (CE ≈ 45 cm2 C−1). Finally, symmetric composite electrochromic devices combining two electrochromic composite film based PEDOT:PSS + BC, via a lithium-based electrolyte membrane plastified with PMMA, show good stability, nice reversibility, and simultaneously reversible color change from dark blue to transparent.