Duleepa, P.K.D. and Pitigala, P. and Senevirathna, Indika. M. K. and Perera, Susira . V. P. and Tennakone, Kirthi (2006) Dye-multilayer semiconductor nanostructures. Comptes Rendus Chimie, 9 (5-6). 605-610 .
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Broadening of the spectral response of dye-sensitized semiconductor devices is one of the major issues confronting practical application of dye-sensitization. It is the main factor limiting the energy conversion efficiencies of dye-sensitized solar cells. Synthesis of dyes with broader spectral response has been attempted as a possible strategy. The other method is to adopt more than one pigment. However, the straightforward ways of doing this has been unsuccessful owing to the quenching and the insulating effect of thick dye layers composed of many components. Again, if several dyes are homogeneously dispersed over the nanocrystalline surface at sub-monolayer coverage of each dye, the problem of quenching and insulation may be avoided. Here we face another constraint. In order to achieve full absorption at the peak wavelength of each dye, the film thickness needs to increase, the limit for which is the diffusion length of carriers in the nanocrystalline matrix. We have found some ways of circumventing the above difficulties and construct model solar cells sensitized with more than one pigment. A solar cell of the configuration n-TiO2/D1–D2/p-CuSCN was constructed, where D1 = an ionic dye bonded to the TiO2 surface and D2 = ionic dye of opposite charge, electrostatically bonded to D1. In another cell, two dyes D1 and D2 are used form the heterostructure n-TiO2/D1/ S/ D2/p-CuSCN, where S is an ultra-thin barrier of a high band gap semiconductor. Each of the above double dye-systems showed efficiencies above the equivalent single dye systems. These methods can also be extended to liquids cells. A better suppression of electron-hole recombination was found to be an additional advantage of multiple dye systems. The mechanisms of operation of these devices via electron or energy transfer or electron tunneling will be discussed.
|Subjects:||Physical Science > Nanophysics|
Physical Science > Nano objects
Material Science > Nanochemistry
Material Science > Nanostructured materials
|Divisions:||Faculty of Engineering, Science and Mathematics > School of Physics|
Faculty of Engineering, Science and Mathematics > School of Chemistry
|Deposited On:||28 Oct 2009 05:21|
|Last Modified:||28 Oct 2009 05:21|
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