Several viologen electrochromic devices with different thicknesses on glass substrates were constructed, using a mixture of 4,4’-bipyridine and 1-bromoethane. The thickness of each device was fixed using a thermoplastic spacer. The devices were electrochemically tested with optical and impedance analysis. The range of the transmittance change is highly dependent on thickness. The electrical behavior of the material and the physical and chemical characteristics are derived from the proposed electrical equivalent circuit model. A simple Randles circuit including a Warburg diffusion impedance element, a charge transfer resistance and a double layer capacitive element is proposed for the fittings process. Variations on thickness of internal layer of devices lead to use a short or an open circuit Warburg element. A threshold potential, from which the device is colored, indicates the charge diffusion effects.

Aiming at clarifying the opto-electronic properties of ZnO based n-type Transparent Conducting Oxides, TCOs, properties of ZnO thin films are studied as a function of cationic doping. In addition to commonly reported, Al and Ga trivalent dopant, similar performances are reported for Si doping. In the visible region, ZnO:Si (3 %) thin film exhibit a transmittance higher than 80 % for a resistivity as low as 8x10-4 Ω.cm when grown at 100 °C under 1.0 Pa oxygen pressure. The influence of tetravalent cations as dopant is also investigated through Sn and Ge additions. It shows that not only the oxidation state plays a role but also the cation nature. Indeed, ZnO:Sn thin films are insulating whereas the ZnO:Ge thin films are conductive with resistivity values higher than the ones of ZnO:Si thin films.

Mg1-zCaz (0.03 < z < 0.17) alloy thin films covered with thin Pd are hydrogenated using 4% H2 in Ar under atmospheric pressure at room temperature. The optical indices, which are refractive indices and extinction coefficients, in the wavelength between 250 and 1700 nm of these hydrides were evaluated with spectroscopic ellipsometry. The evaluated refractive indices were about 2.0 for all hydrides, while the extinction coefficients showed the values less than 0.06 in the visible range for hydride with Ca composition of z ≤ 0.08 and the coefficients increased sharply to more than 0.3 with Ca composition z > 0.08.

Electrochromic (EC) devices are able to vary their throughput of visible light and solar energy by the application of a voltage. They are of much interest for “smart” windows in buildings and are able to create energy efficiency, occupant well being, and security. This paper gives a survey over oxide-based EC device technology and also presents some recent advances regarding EC thin films of mixed metal oxides, nanoparticle-containing electrolytes to join these films, and metal-based transparent electrical conductors needed to apply the voltage.

Cobalt hydroxide thin films with a thickness of 100 nm were deposited onto glass, Si and indium tin oxide (ITO)-coated glass substrates by reactively sputtering a Co target in H2O gas. The substrate temperature was varied from -20 to +200°C. The EC performance of the films was investigated in 0.1 M KOH aqueous solution. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy of the samples indicated that Co3O4 films were formed at substrate temperatures above 100°C, and amorphous CoOOH films were deposited in the range from 10 to -20°C. A large change in transmittance of approximately 26% and high EC coloration efficiency of 47 cm2/C were obtained at a wavelength of 600 nm for the CoOOH thin film deposited at -20°C. The good EC performance of the CoOOH films is attributed to the low film density and amorphous structure.