Solution Processed Silver Nanoparticles in Dye-Sensitized Solar Cells

A plasmonic effect of silver nanoparticles (Ag NPs) in dye-sensitized solar cells (DSSCs) is studied. The solutions of silver nitrate in isopropanol, ethylene glycol, or in TiO2 sol were examined as possible precursors for Ag NPs formation. The solutions were dip-coated on the top of the porous TiO2 layer. The results of optical measurements confirmed the formation of Ag NPs throughout the porous TiO2 layer after the heat treatment of the layers above 100°C. Heat treatment at 220°C was found to be optimal regarding the formation of the Ag NPs. The porous TiO2 layers with Ag NPs have been evaluated also in DSSC by measuring current-voltage characteristics and the external quantum efficiency of the cells. In addition, the amount of adsorbed dye has been determined to prove the plasmonic effect in the cells. The I-V characterization of the DSSCs revealed an increase of the short circuit current in the presence of Ag NPs although the amount of the attached dye molecules decreased. These results confirm that the performance enhancement is related to the plasmonic effect. However, neither a thin sol-gel TiO2 layer nor poly(4-vinylpyridine) shells provide effective protection for the long term stability of the Ag NPs against the corrosion of I3-/I- based electrolyte

Inkjet printing of tungsten sol-gel ink

Tungsten (VI) oxide − WO3 is one of the widely studied inorganic semiconductors with outstanding chromogenic properties. Its unique optical and electrical properties enable application in energy efficient systems (e.g. smart windows), sensors, displays, storage units, electric and photo catalysts and solar cells. The WO3 layers are mostly made by expensive vacuum sputtering (PVD), chemical vapour deposition (CVD) and electro-deposition, but it is also possible to deposit layers from sol-gel solutions using dip-coating or spin-coating. On the other hand printing of the WO3 layers is unexplored area, although enabling flexibility of the substrates, patterning, multi-layer deposition and R2R mass production favouring low cost of the final devices. According to our knowledge this is the first report showing the feasibility of inkjet printing of tungsten sols

In-depth rheological characterization of tungsten sol-gel inks for inkjet printing

The inkjet printing of the functional materials prepared by the sol-gel route is gaining the attention for the production of the variety of the applications not limited to the printed boards, displays, smart labels, smart packaging, sensors and solar cells. However, due to the gelation process associated with the changes from Newtonian to non-Newtonian fluid the inkjet printing of the sol-gel inks is extremely complex. In this study we reveal in-depth rheological characterization of the WO$_3$ sols in which we simulate the conditions of the inkjet printing process at different temperature of the cartridge (20–60 °C) by analyzing the structural and rheological changes taking place during the gelation of the tungsten oxide (WO$_3$) ink. The results provide the information on the stability of the sol and a better insight on the effects of the temperature on the gelation time. Moreover, the information on the temperature and the time window at which the inkjet printing of the sol-gel inks could be performed without clogging were obtained. The WO$_3$ ink was stable in a beaker and exhibited Newtonian flow behavior at room temperature over 3 weeks, while the gelation time decreased exponentially with increasing temperature down to 0.55 h at 60 °C