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A hybrid system in which the counter electrode is exchanged with a redox couple dissolved in the electrolyte is an alternative to a “sandwich” type electrochromic (EC) device. We have developed a solid redox (tetramethylthiourea/tetramethylformaminium disulfide dication TMTU/[TMFDS]2+) electrolyte based on organically modified silane matrix. The EC device employing a solid electrolyte colors homogeneously, visible transmittance (Tvis) changes from 60% to 5%, at −1.5 V within less than 5 min when 240 nm cubic WO3 layer is employed. The results show that solidification of the electrolyte does not affect coloring kinetic, but the reduction of [TMFDS]2+ to TMTU at the Pt electrode significantly slows bleaching and reduces the self-bleaching of the device. Moreover, the EC device employing solid electrolyte colors homogeneously and is colorless in the bleached state (C, a and b values are below 10).

The transmittance of a photochromic (PC) window is reduced in sunlight but returns to its original value in the dark similar to photo-sensitive sun glasses. A 30 cm × 30 cm double glazed window containing a PC multi-layer coating on a single glass pane has been developed. A single PC glass pane can be used to build a window with a low heat transfer coefficient, e.g. double or triple glazed unit, using existing technology. To develop the PC glass with a multi-layered coating that combines chromogenic and photoactive materials we employed sol-gel chemistry approaches and up-scaled the synthesis. Double glazed windows have been assembled using PC glass with two different layer configurations. The transmittance (Tvis) was reduced from 76% to 35% under outdoor solar radiation (750 W/m2) within 15 min.

We report on the development of WO3 layers with increased symmetry induced by the incorporation of titanium into a crystalline WO3 matrix. The atomic ratio between W and Ti was varied stepwise from 100:1 to 100:20 with pure WO3 layers, made using peroxo sol–gel synthesis, as a reference. Layers were then formed by dip-coating from the corresponding sols. IR spectroscopy and XRD analysis of layers and powders heat-treated at 450 °C proved that the presence of titanium ions induces ordering and increases the symmetry of WO6 octahedra in the WO3 crystalline matrix leading to the transformation of the cell symmetry from monoclinic through tetragonal up to the cubic. Cyclic voltammetry confirmed that this increased symmetry leads to an up-shift in redox potential, which favors the coloration of the layers in photochromic devices. According to our knowledge, this is the first report of colorless cubic WO3 layers, which have potential applications in optoelectronic devices and sensors.

The performance of dye-sensitized solar cells, based on pure and binary ionic liquid electrolyte with different iodine concentrations, have been evaluated under 1 sun illumination and different cells temperature between 5 and 55 °C. At lower temperatures a short-circuit current ( J SC ) may be limited by the diffusion of tri-iodide. In this situation J SC increases with increasing temperature, while at higher temperatures the J SC decreases due to more pronounced recombinations. We find a maximum for J SC at intermediate temperatures. This maximum shifts to lower temperatures by increasing iodine concentration. At a certain temperature different iodine concentration is optimal for different ionic liquids employed in the electrolyte. The open circuit voltage monotonically decreases with temperature while the conversion efficiency is basically dominated by temperature dependence of J SC .

A novel titanium oxide paste based on Pechini sol–gel method and nanocrystalline titanium oxide powder have been successfully developed. Titanium oxide layers possess high inner surface area assuring high dye loading and well-connected nanocrystalline grains assuring good electron transport within the layer. The dye-sensitized layers have been used to assemble dye-sensitized solar cells with acetonitrile- and ionic liquid-based electrolyte. Overall conversion efficiencies of dye-sensitized solar cells (DSSCs) determined under standard test conditions (100 mW/cm 2 , 25 °C and AM 1.5 G) are 10.2% for acetonitrile and 7.3% for ionic liquid-based electrolyte.