Large increases in photocurrents and solar conversion efficiencies by UV illumination of dye sensitized solar cells
Ultraviolet (UV) treatment of dye sensitized solar cells (DSSCs) containing tetra-n-butylammonium iodide electrolyte increases photocurrents dramatically. The effect remains after cessation of UV illumination. Depending upon the photosensitizing dye, the increase in photocurrent can be as much as 2 orders of magnitude. The photocurrent increase more than compensates for slight decreases in photovoltage and fill factor, resulting in overall solar conversion efficiency increases up to 45 ?? for some dyes. The primary effect of the UV treatment appears to be a positive shift in the conduction band of the nanocrystalline titanium dioxide, which promotes electron injection from the dye. The dyes and the solar cells are both found to be stable to this treatment. This effect offers the ability to tune the properties of the semiconductor to match the requirements of a specific dye, thus providing a versatile analytical tool for characterizing DSSCs while also enabling the use of new classes of sensitizing dyes. This letter describes the UV effect and summarizes the results of its application to a number of perylene-based sensitizers and two ruthenium bipyridyl sensitizers.
Supercritical carbon dioxide as a solvent for deposition of a tailored dye in dye sensitized solar cells
We report a new technique whereby dyes can be deposited onto metal oxide surfaces using supercritical carbon dioxide (scCO2) for use in solar cell applications. This process eliminates the need for hazardous organic solvents and waste solvents generated during the dyeing process. The solubility of a perylene anhydride dye in scCO2 is enhanced by the incorporation of fluorinated alkyl subsituents and the use of masked carboxylic binding groups. This allows fast deposition of the dye onto the TiO2 photoanode, resulting in efficient photovoltaic performance. The unreacted dye is then easily recovered in a solid form after the deposition process by venting the carbon dioxide.
Maniam, Subashani,Holmes, Andrew B.,Krstina, Julia,Leeke, Gary A.,Collis, Gavin E.
p. 3329 - 3332
(2012/02/01)
New perylenes for dye sensitization of TiO2
We describe a new generation of perylene photosensitizers based upon N-(2,5-di-tert-butylphenyl)perylene-3,4- dicarboximide. The new sensitizers have more favorable energetics for electron injection into TiO2 and better light absorption properties for solar conversion than previous sensitizers based upon perylene tetracarboxylic acid dianhydride. Syntheses, absorption properties, and electrochemical potentials for the new perylenes are reported. We compare the solar conversion efficiencies of the dyes in the dye sensitized solar cell (DSSC) and discuss trends in terms of energetics and structural differences that may affect the injection and recombination processes. These are the highest efficiencies yet reported for perylene sensitizers in the DSSC.
Ferrere, Suzanne,Gregg, Brian A.
p. 1155 - 1160
(2007/10/03)
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