Influence of electrolyte cations on electron transport and electron transfer in dye-sensitized solar cells

Wang, Hongxia & Peter, Laurence M. (2012) Influence of electrolyte cations on electron transport and electron transfer in dye-sensitized solar cells. The Journal of Physical Chemistry C, 116(19), pp. 10468-10475.

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The influence of different electrolyte cations ((Li+, Na+, Mg2+, tetrabutyl ammonium (TBA+)) on the TiO2 conduction band energy (Ec) the effective electron lifetime (τn), and the effective electron diffusion coefficient (Dn) in dye-sensitized solar cells (DSCs) was studied quantitatively. The separation between Ec and the redox Fermi level, EF,redox, was found to decrease as the charge/radius ratio of the cations increased. Ec in the Mg2+ electrolyte was found to be 170 meV lower than that in the Na+ electrolyte and 400 meV lower than that in the TBA+ electrolyte. Comparison of Dn and τn in the different electrolytes was carried out by using the trapped electron concentration as a measure of the energy difference between Ec and the quasi-Fermi level, nEF, under different illumination levels. Plots of Dn as a function of the trapped electron density, nt, were found to be relatively insensitive to the electrolyte cation, indicating that the density and energetic distribution of electron traps in TiO2 are similar in all of the electrolytes studied. By contrast, plots of τn versus nt for the different cations showed that the rate of electron back reaction is more than an order of magnitude faster in the TBA+ electrolyte compared with the Na+ and Li+ electrolytes. The electron diffusion lengths in the different electrolytes followed the sequence of Na+ > Li+ > Mg2+ > TBA+. The trends observed in the AM 1.5 current–voltage characteristics of the DSCs are rationalized on the basis of the conduction band shifts and changes in electron lifetime.

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ID Code: 58201
Item Type: Journal Article
Refereed: Yes
Keywords: dye-sensitized, electron lifetime, electron diffusion length, solar cells
DOI: 10.1021/jp211807w
ISSN: 1932-7455
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Physical Chemistry not elsewhere classified (030699)
Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > MATERIALS ENGINEERING (091200) > Materials Engineering not elsewhere classified (091299)
Copyright Owner: Copyright 2012 American Chemical Society
Deposited On: 14 Mar 2013 23:56
Last Modified: 18 Mar 2013 16:39

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