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Efficient Electron Injection from Acyloin-Anchored Semisquarylium Dyes into Colloidal TiO2 Films for Organic Dye-Sensitized Solar Cells
journal contribution
posted on 2014-04-03, 00:00 authored by Andreas F. Bartelt, Robert Schütz, Christian Strothkämper, Joachim Schaff, Stephan Janzen, Paja Reisch, Ivo Kastl, Manuel Ziwritsch, Rainer Eichberger, Gerda Fuhrmann, David Danner, Lars-Peter Scheller, Gabriele NellesSemisquarylium
dyes use a novel acyloin anchor group to strongly
bind to TiO2 semiconductors. Efficient acyloin anchor mediated
electron injection into nanocrystalline TiO2 is demonstrated,
allowing highly efficient dye-sensitized solar cells with IPCEs >
80%. The acyloin anchor can thus be viewed as a true alternative to
the standard carboxylic acid anchor group. The opto-electronic and
electron injection properties of the most basic semisquarylium dye
SY404 are compared to the modified semisquarylium
dye DD1 and the carboxylic acid anchored indoline dye
D131 using a combination of ultrafast and photoemission
spectroscopy. For SY404, ultrafast injection times of
∼50 fs are found despite a small energetic driving force between
dye excited states and TiO2 conduction band minimum. This
is possible due to the strong electronic coupling of the semisquarylium
dyes to the TiO2 surface mediated by the acyloin anchor.
For a better overlap with the solar spectrum, the semisquarylium dyes
are modified by substitution with a larger donor moiety (DD1). While for DD1 the overall absorption increases, the
injection process slightly slows down; however, it still proves fast
enough for very efficient injection. Compared to the carboxylic acid
anchored indoline dye D131, the SY404 dye
injects more than seven times faster despite a ∼150 meV smaller
driving force.
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indoline dye D 131semisquarylium dye SY 404TiO 2 surfaceelectron injection propertiescarboxylic acidnanocrystalline TiO 2novel acyloin anchor groupTiO 2 semiconductorsEfficient acyloin anchorcarboxylic acid anchor groupsemisquarylium dyessemisquarylium dye DD 1Efficient Electron Injectionacyloin anchorTiO 2 conduction bandSY 404 dyeColloidal TiO 2 FilmsIPCE
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