Dipyrrin complexes as dyes for dye-sensitised solar cells : a thesis submitted in partial fulfilment of the requirements for the degree of Masters in Science in Chemistry at Massey University, Palmerston North, New Zealand
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Date
2009
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Massey University
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Abstract
With increasing concerns of global warming and the impending exhaustion of fossil fuels
attention is being turned to renewable sources of energy. The sun supplies 3 x 1024 J per
year to the earth which is around 104 times more energy than what the human race
consumes. The world’s energy needs would be satisfied if a mere 0.1% of the planet’s
surface was covered with solar cells(< = 10%)1, causing the conversion of solar energy
(sunlight) into electricity to represent a very practical renewable source.
Past research into solar energy has produced a photovoltaic device, which when coupled
with highly coloured coordination compounds, enables this conversion. This device is
known as a dye-sensitised solar cell (DSSC). Further research has been conducted into the
properties of the dyes, and has shown that highly coloured coordination compounds are
able to convert solar energy into electrical energy with the highest efficiencies. The
dominant compounds in this area to date have been Grätzel’s ruthenium complexes and
porphyrins.
However, there exists a class of smaller compounds called dipyrrins, described most
simply as “half a porphyrin”, which possess many of the attractive qualities for DSSC
dyes. Although there are no examples of ruthenium-dipyrrin complexes in the literature,
the combination of advantageous properties from both components represent very
attractive synthetic targets with huge potential as dyes for DSSCs.
The objectives of this thesis were firstly to develop a series of dipyrrin complexes which
would be suitable as dyes for DSSCs; then to fully characterise the complexes and
investigate the spectroscopic properties of each complex; and finally to determine the
suitability of the complexes as dyes for DSSCs. These objectives were fully met, resulting
in a set of generic target compounds characterised via 1H NMR, 13C NMR, mass
spectrometry (ESI-MS), elemental analysis, and x-ray crystallography. From analyses of
the UV-visible, fluorescence, emission, and Raman spectra; and electrochemistry results;
the complexes were concluded to be suitable as dyes for DSSC’s. An additional bonus is
that the syntheses for these complexes are applicable to any dipyrrin, thus aiding future
studies into the use of dipyrrins as dyes for DSSC’s. This thesis summarises the findings
of the above outlined research project.
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Keywords
Dye-sensitised solar cells, Dipyrrin complexes, Photovoltaic devices, DSSC dyes