Programm Photovoltaik Ausgabe 2008 ... - Bundesamt für Energie BFE

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Obtaining long-term stability for DSCs at temperatures of 80~85°C had remained a major challenge for
over 10 years and has only recently been achieved. Stabilization of the interface by using selfassembly
of sensitizers in conjunction with amphiphilic coadsorbents has been particularly rewarding.
Stable operating performance under both prolonged thermal stress (at 60�C and 85°C) and AM 1.5
light soaking conditions has been possible. These devices retained 97.7% of their initial power conversion
efficiency after 1,000 hr ageing. An analysis on DSC stability shows that in principle, DSCs
can function in a stable manner for over 20 years, if the macro-engineering issues are rightly addressed
(9). This has recently been verified experimentally by an industrial partner. The stability of
parameters of a state-of-the art cell is presented in fig. 5.
In a further development a new concept, recently introduced, uses eutectic mixtures of molten salts as
redox electrolytes. Excellent stability and an unprecedented efficiency of 8.2% are noted under air
mass 1.5 global (AM 1.5G) illumination for a DSC, employing, along with the eutectic, a nanocrystalline
titania film and the amphiphilic heteroleptic ruthenium complex Z907Na as sensitizer. The results
are of great importance for progress towards large-scale outdoor applications of mesoscopic dyesensitized
solar cells.
In addition to the enhanced performance and reliability of individual DSC devices, their use as components
of a tandem system has already been mentioned. One device associated a DSC unit with a
spectral response cutoff near 700nm with a thin film solid state cell, in this case a I-III-(VI)2 cell such as
CuInSe2, so that the combined device has a sensitivity extended into the infrared about 1150nm
(Fig.6). With the cells in optical and electrical series there is an enhanced Voc of up to 2V, and a solar
spectral conversion efficiency of 15% when the fill factor reaches 0.74. Patent protection of the associated
intellectual property has bee obtained (10). A patent on a metal oxide film for use in a tandem
cell photoelectrolysis device was also obtained during 2007(11).
Fig. 6: Incident photon conversion efficiency of the tandem device comprising a DSC in optical series
with a thin film solid state cell with complementary optical absorption characteristics.
National Cooperation
The national cooperation involves participation in the Competence Centre for Energy and Mobility
(CCEM), initiatiated by the Council of the Swiss Federal Polytechniques (ETH-Rat) and managed by
the Paul Scherrer institute. The particular activity is within the cooperation on "Cost Effective Thin Film
Photovoltaics for Future Electricity Generation" directed by Dr. F. Nüesch (EMPA). The Swissregistered
company Greatcell Solar S.A. holds a licence to the intellectual property of the laboratory
on photovoltaics in association with Dyesol PLC, Australia. The work of the laboratory is also supported
by the Swiss National Fund for Scientific Research (SNF/FNS) as a contribution to its International
Materials Initiative.
A significant Swiss action to promote the dye-sensitised photovoltaics technology was the International
Dye Solar Cell Industrialisation Conference, 2007, held as part of the NanoEurope 2007 Fair
and Conference, 11 – 13 September 2007 at the Olma Conference Centre, St.Gallen. The key concept
structuring the Conference was defined by the Chairman, Prof. A. Luzzi, in his assertion that the
technology now stands "on the brink of industrialisation". The event was designed to provide a forum
for meeting and interaction of the world DSC community, to strengthen that community at large and
specifically to promote and accelerate the numerous DSC commercialisation programmes. There is
the implication that industrialisation has not yet been completed, but given the significantly increased
DSC development efforts worldwide, confidence in successful exploitation of the technology on an
industrial scale is now confirmed as realistic in the short term.
Dye-Sensitised Nanocrystalline Solar Cells, M. Grätzel, EPFL Seite 111 von 288