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Title:
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Charge Transport and Recombination in a Nanoscale Interpenetrating Network of n-Type and p-Type Semiconductors: Transient Photocurrent and Photovoltage Studies of TiO2/Dye/CuSCN Photovoltaic Cells
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Author(s):
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Published by:
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Publication date:
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ECN
Solar Energy
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1-3-2004
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ECN report number:
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Document type:
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ECN-RX--04-034
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Article (scientific)
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Number of pages:
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9
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Published in: Journal of Physical Chemistry B (American Chemical Society), , 2004, Vol.108 (14), p.4342-4350.
Abstract:
Solid-state dye-sensitized photovoltaic cells have been fabricated with
TiO
2 as the electron conductor and CuSCN as the hole conductor.
These cells involve the nanoscale mixing of crystalline n-type and p-type
semiconductors in films that are more than 100 times thicker than the
individual n- and p-type domains. Charge transport and field distribution
in this kind of material are as yet unexplored. We have used photocurrent
and photovoltage transients, combined with variation in the layer thickness,
to examine the limiting factors in charge transport and recombination.
Charge transport (t1/2
~200 Ìs) is found to
be similar to that in dye-sensitized electrolyte cells. Recombination
at Voc (t1/2 150 Ìs) is 10 times faster than in electrolyte
cells, and recombination at short circuit (t1/2
450 Ìs) is 100 times faster. In the solid-state
cells, the similarity of the charge transport and recombination rates
results in a low fill factor, and photocurrent losses, both important
limiting factors of the efficiency. A simple model is given, and suggestions
are made for improvements in efficiency.
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