Journal article

Improved Photon-to-Current Conversion Efficiency with a Nanoporous p-Type NiO Electrode by the Use of a Sensitizer-Acceptor Dyad

A perylene imide sensitizer and a covalently-linked perylene imide-naphthalene diimide dyad were prepd. and characterized by absorption and emission spectroscopies, electrochem., and spectroelectrochem. These compds. were chemisorbed on nanoporous Ni oxide electrodes and then studied by femtosecond transient absorption spectroscopy in the presence of a redox active electrolyte (I3-/I-). In both compds., upon excitation of the perylene imide unit, an electron is efficiently ejected from the valence band of NiO to the dye with an av. time const. of ∼0.5 ps. In the case of the dyad, the excess electron is shifted further onto the naphthalene diimide unit, creating a new charge sepd. state. The latter exhibits a substantial retardation of the charge recombination between the hole and the reduced mol. compared with the perylene imide sensitizer. The photo-action spectra of a sandwich dye-sensitized solar cell (DSSC) composed of NiO films and these new dyes were recorded, and the absorbed-photon to current conversion efficiency (APCE) was 3 times higher with the dyad than with the perylene imide dye. The max. APCE of ∼45% is the highest value reported for a DSSC based on a nanostructured metal oxide p-type semiconductor.


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