NANOCRYSTALLINE TiO2 ELRCTRODES FOR DYE-SENSITIZED SOLAR CELLS
 
Emil Indrea1, Simina Dreve1, Dan T. Silipas1,  Virginia Danciu2, Veronica Cosoveanu2, Nascu Horea-Iustin3 

1National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca,  ROMANIA, 
2Babes-Bolyai University, Faculty of Chemistry and Chemical Engineering, Arany Janos Str., 11, Cluj-Napoca, ROMANIA
3Technical University of Cluj-Napoca, ROMANIA
eindrea@s3.itim-cj.ro, vdanciu@chem.ubbcluj.ro, nascuh@yahoo.com

Solar cells on dye-sensitized nanocrystalline films of TiO2 are low-cost alternatives to conventional solid-state devices [1]. The photovoltaic system is based on the sensitization of nanocrystalline semiconductor oxide films by transition metal charge transfer sensitizers. Nanocrystalline semiconductor films are constituted by a network of mesoscopic TiO2 particles witch are interconnected to allow for electronic conduction to take place. The pores between the particles are filled with a liquid conductor, such as a redox electrolyte. The fundamental processes involved in any photovoltaic conversion process are absorption of sunlight, the generation of electric charge by light and the collection of charge carriers to produce electricity [2]. Because of their ultra low density, high homogeneity and high surface area, TiO2 aerogels are attractive for their applications in solar energy conversion, photocatalysis [3]. 
In the present work our attention was focused on the obtaining dye-sensitized solar cells that incorporate two substrates at least one of which has been coated with a transparent conducting oxide (TCO), referred to as the primary electrode and the other, the counter electrode, coated with TCO or a non-corrosive metal such as titanium upon which is coated a very thin layer of platinum. A porous layer of a semiconductor such as TiO2 is deposited on the conductive surface of the TCO. The nanoporous TiO2 film was deposited onto a sheet of ITO conducting glass (sheet resistance ~ 30 cm-2).  A colloidal TiO2 suspension was obtained by grinding 2 g of  TiO2 powder in 2 mL of distilled H2O and 0.2 mL of acetylacetone, in a mortar with a pestle, for about 30 min. Finally 8.0 mL of distilled water and 0.1 mL Triton X-100 were slowly added with continuous mixind for 10 min. Several drops of above TiO2 suspension were spreaded onto the surface using a glass rod. The electrode were dried in air and fired at 3500C for 60 min under ambient atmosphere. 
Several complementary investigation techniques like BET, SEM, SAXS, Raman and XRD were used to follow the influence of the reactants molar ratio and thermal treatment on the TiO2 aerogel structures.

References
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2.	“New Approaches for Energy Conversion at Dye Sensitized Electrodes.”, Bergeron, B.V.; Meyer, G.J. in Photovoltaics for the 21st Century II, McConnell, R. D.; Kapur, V. K. (Eds.), The Electrochem. Soc. INC., Pennington, NJpp 173-183, 2001.
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