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

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.