NSTI Nanotech 2009

Evaluation of I-V characteristics of ordered mesoporous TiO2 electrode for dye sensitized solar cells

A. Vats, R. Shende, J. Puszynski
South Dakota School of Mines & Technology, US

Keywords: dye sensitized solar cells, sol-gel, ordered mesoporous, TiO2, supercritical CO2

Abstract:

The present studies are focused on two major areas a) synthesis of ordered mesoporous TiO2 thin film electrodes and tuning pore size of the mesoporous thin film electrodes using chemical modification techniques for DSSC applications, and b) IV evaluation of these novel electrodes. Currently, DSSC’s utilizes 5-20 μm size films of TiO2 nanocrystals, which provides sufficient anchoring sites for dye sensitizers and yields reasonably well energy conversion. The current state of the art DSSC is reported to have an overall efficiency of 11% and there is a big thrust towards increasing the overall efficiency of these photo-electrochemical devices in DSSC community. In this direction, one goal has been to tune the porosity in the acceptor layer (TiO2 electrode). The nature of charge transport in these electrolyte permeated porous acceptor electrodes is ambipolar, mass transport limitation due to irregular morphology of TiO2 nanocrystalytes and distribution of pore size in the film. In this work, we present the synthesis of ordered mesoporous electrodes using two distinct approaches. The prevailing processes will be further modified to tune the pore diameter in the range of 6-50 nm in the ordered electrode film by using suitable chemical modifying agents. The Figure-1a shows the order porosity in TiO2 thin films on silicon substrate synthesized using surfactant template assisted sol-gel technique, whereas Figure-1b & 1c show the thin films synthesized using the supercritical CO2 assisted infusion of Ti – alkoxide precursor into 100 nm thick solid block co-polymer template containing acid catalyst. The SEM micrographs in figure-1b show uniform size TiO2 particles arranged in a partially ordered manner. In Figure-1c, it can be observed that the TiO2 particles are porous having interparticle pore size of approx 2 ~ 4 nm. We anticipate that by using certain non-polar organic modifiers pore swelling can be achieved. We will present synthesis of ordered TiO2 electrodes and their characterization, fabrication of DSSC devices and evaluation of their IV characteristics.
 
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