Conjugated electrochromic (EC) polymers for flexible EC devices (ECDs) generally lack a fully colorless bleached state. A strategy to overcome this drawback is the implementation of a new sidechain‐modified poly(3,4‐ethylene dioxythiophene) derivative that can be deposited in thin‐film form in a customized high‐throughput and large‐area roll‐to‐roll polymerization process. The sidechain modification provides enhanced EC properties in terms of visible light transmittance change, Δτ_v = 59% (ΔL* = 54.1), contrast ratio (CR = 15.8), coloration efficiency (η = 530 cm² C⁻¹), and color neutrality (L* = 83.8, a* = −4.3, b* = −4.1) in the bleached state. The intense blue‐colored polymer thin films exhibit high cycle stability (10 000 cycles) and fast response times. The design, synthesis, and polymerization of the modified 3,4‐ethylene dioxythiophene derivative are discussed along with a detailed optical, electrochemical, and spectroelectrochemical characterization of the resulting EC thin films. Finally, a flexible see‐through ECD with a visible light transmittance change of Δτ_v = 47% (ΔL* = 51.9) and a neutral‐colored bleached state is developed.

Magnesium fluoride sols for the wet chemical processing of porous MgF₂ antireflective coatings were prepared by the reaction of MgCl₂ with HF. The formation and crystallisation of MgF₂ nanoparticles were followed by ¹⁹F NMR spectroscopy, X-ray diffraction (XRD) and dynamic light scattering (DLS) in the liquid phase. The crystallization of the resulting films was monitored by XRD experiments. At temperatures exceeding 550 °C the film material and glass substrates undergo a chemical reaction, MgO is formed and SiF₄ evaporates as a volatile product. Microstructure and optical properties were characterized as a function of the annealing temperature. The mechanical stability of MgF₂ films was evaluated by the Crockmeter test using both felt and steel wool. It is shown that porous MgF₂ films prepared by this synthesis have a vast potential for the large-area processing of antireflective coatings.

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.

Magnesium doped thin films of CuCrO₂ and CuAl_0.5Cr_0.5O₂, both exhibiting delafossite structure, were synthesized via sol–gel processing. The influence of the dopant on the phase development during the subsequent 2-step annealing procedure was monitored by X-ray diffraction. Systematic variation of the dopant concentration between 2.5 and 15% revealed that the Mg inhibits crystallization and stabilizes spinel phases against thermal decomposition, whereby the amount of impurities in the delafossite films is increased. Nevertheless the p-type conductivity and surprisingly the transmittance of the CuCrO₂ films were improved by Mg doping by two orders of magnitude and 16%, respectively. On the contrary the performance of the CuAl_0.5Cr_0.5O₂ films hardly profits from Mg doping. The Seebeck-coefficients of this system even imply a decreasing charge carrier density with increasing dopant concentration, which can only be interpreted as an expulsion of the native defects acting as strong intrinsic doping. The band gap of both oxides remains constant, however.