Large-Area Electrochromic Devices on Flexible Polymer Substrates with High Optical Contrast and Enhanced Cycling Stability

Large-area electrochromic devices (ECDs) based on a cathodically-coloring, side chain-modified poly(3,4-ethylene dioxythiophene) (PEDOT) derivative and anodically-coloring Prussian blue (PB) are assembled by a customized sheet-to-sheet (S2S) lamination process. The ECDs with two complementary switching "half-cells", based on flexible PET-ITO substrates, offer enhanced optical properties in terms of visible light transmission change (4-53%), contrast ratio (CR = 93.4) and color neutrality (L* = 77.9, a* = -5.9, b* = -0.6) in the bleached state. The cycling stability is monitored for up to 10 000 switching cycles (97% charge retention). The reported optical, electrochemical, and in operando (in situ) spectroelectrochemical data are obtained from small laboratory-scale ECDs (active area: 5 × 5 cm2). These results, the homogeneity of the large-area devices and the scalability of the S2S lamination process are confirmed by measurements on the large ECDs with an active area of 45 × 65 cm2. This large-area electrochromic film technology with high optical contrast and enhanced cycling stability offers an excellent perspective for further development and scale-up towards pilot production and the commercialization of flexible ECDs upon their unique materials and processing characteristics.