Highly efficient photocathodes for dye-sensitized tandem solar cells

Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices. High-efficiency DSCs typically operate as photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconduc...

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Bibliographic Details
Published in:Nature materials 2010-01, Vol.9 (1), p.31-35
Main Authors: Bäuerle, P, Bach, U, Nattestad, A, Mozer, A. J, Fischer, M. K. R, Cheng, Y.-B, Mishra, A
Format: Article
Language:English
Subjects:
Biomaterials
Chemistry and Materials Science
Condensed Matter Physics
Construction
Differential scanning calorimetry
Dyes
Electrodes
Energy conversion
Injection
letter
Materials Science
Nanotechnology
Optical and Electronic Materials
Photocathodes
Photovoltaic cells
Semiconductors
Silicon
Solar cells
Thin films
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Summary:Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices. High-efficiency DSCs typically operate as photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconductors. Dye-sensitized photocathodes (p-DSCs) operate in an inverse mode, where dye-excitation is followed by rapid electron transfer from a p-type semiconductor to the dye (dye-sensitized hole injection). Such p-DSCs and n-DSCs can be combined to construct tandem solar cells (pn-DSCs) with a theoretical efficiency limitation well beyond that of single-junction DSCs (ref. 4). Nevertheless, the efficiencies of such tandem pn-DSCs have so far been hampered by the poor performance of the available p-DSCs (refs 3, 5-15). Here we show for the first time that p-DSCs can convert absorbed photons to electrons with yields of up to 96%, resulting in a sevenfold increase in energy conversion efficiency compared with previously reported photocathodes. The donor-acceptor dyes, studied as photocathodic sensitizers, comprise a variable-length oligothiophene bridge, which provides control over the spatial separation of the photogenerated charge carriers. As a result, charge recombination is decelerated by several orders of magnitude and tandem pn-DSCs can be constructed that exceed the efficiency of their individual components.
ISSN:1476-1122
1476-4660
DOI:10.1038/nmat2588