A contribution to climate protection - Electrochromic windows fabricated with the sol-gel technology

[no abstract available

A contribution to climate protection - electrochromic windows fabricated with the sol-gel technology

[no abstract available

Electrochromism of NiO-TiO2 sol gel layers

Films of NiO-TiO2 with Ni concentration of 100, 90, 87, 83, 75, 66, 50 and 33 mol% have been obtained via the sol-gel route by dip coating technique and sintered in air between 250 and 500°C using ethanolic sols of nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O) and titanium n-propoxide (Ti(O-CH(CH3)2)4) precursors. Xerogels obtained by drying the sols have been studied up to 900°C by thermal analysis (DTA/TG) coupled to mass and IR spectroscopy. The crystalline structure and morphology of the layers in the as deposited, bleached and colored states were determined by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy Their electrochromic properties have been studied in 1 M KOH aqueous electrolyte as a function of the layer composition, thickness and sintering temperature. Deep brown colour with reversible transmittance changes have been obtained using cycling voltammetry and chronoamperometry processes. The best composition to get stable sols, a high reversible transmittance change and fast switching times (<10 s) was obtained with double NiO-TiO2 layers 160 nm thick having 75% Ni molar concentration, and sintered between 300 and 350°C. The mechanism of coloration and morphology transformation of the layer during cycling are discussed in terms of an activation and degradation period. The results are in agreement with the accepted Bode model

Grey, brown and blue coloring sol-gel electrochromic devices

Pure and doped niobium oxide (Nb2O5) layers are electrochromic (EC) materials which change their colour by insertion of Li+ ions from transparent to brown, grey or blue depending on the crystallinity of the layer. EC-devices with the configuration K-glass / EC-layer / composite electrolyte / Ion-storage (IS) layer / K-glass, were produced using different Nb2O5 EC-layers, a (CeO2)x(TiO2)1-x (x=0.45) IS-layer and an inorganic-organic composite electrolyte to which a small amount of water (up to 3 wt%) was added. The grey coloring all-solid-state sol-gel devices fabricated with Nb2O5:Mo coatings show a high reversible colouration (DeltaOD = 0.3) and a longterm stability of more than 55000 switching cycles. Large area EC-devices (30 cm x 40 cm) show a transmittance change between 60% and 25% at 550 nm after galvanostatic colouration and bleaching for 3 min and a colouration efficiency of 27 cm²/C. The results obtained with blue and brown colouring Nb2O5 EC-layers and a comparison with blue coloring WO3 layers are also presented

Large area production of optical coatings and devices by the sol-gel process

[no abstract available

Transparent conductive oxides for coating applications

Transparent, conductive oxides (TCOs) applied as coatings find multiple applications in various areas such as flat panel display setups, as electrodes in touch-screen panels, electrochromic devices, solar cells and in architectural applications for example as IR reflectors. The favored material in the class of TCOs is still ITO - Sn-doped In2O3 - due to its unique combination of high transparency and electrical conductivity. Though already very good, the potential of the ITO coatings with regard to their conductivity leaves some space for future improvements. Also ITO as a material has some serious drawbacks, such as limited availability and high costs. this work presents some stratgies to overcome these obstacles. One way to enhance the conductivities of alternative materials is to use carbon nanotubes as a dopant. This strategy was tested for ATO (Antimony-doped Tin Oxide), Titan dioxide and AZO (Aluminium-doped Zinc oxide). The results for these materials are presented. In coatings of ITO on glass or polymeric foils usually silica-based binders are used. They have the disadvantage to reduce the contact between the highly conducting grains and thus reduce overall conductivity in the composite. The matrix between the nanoparticles can be improved by several measures. Experiments with relevance in this direction are discussed. A third strategy aims at the reduction of costs in the process of ITO fabrication. Here one way to go is to use an electrochemical synthesis method. Results of the line of development are presented. Other strategies comprise the suitable processing of materials with a lower intrinsic conductivity or the search for materials with high intrinsic conductivity close to that of ITO. Exmples are presented and discussed