Research into dye sensitised solar cells has increased in recent years as the search for a viable low cost, renewable energy source continues. The synthesis and characterisation of an array of symmetrical and asymmetrical zinc and ruthenium centred phthalocyanines and naphthalocyanines are presented in this work. Certain compounds were designed so that they would possess a carboxylic acid group which could be utilised to chemisorb the compound to a titanium dioxide surface. The dye sensitised titania electrodes were studied as potential photoanodes in dye sensitised solar cells. The use of symmetrical and asymmetrical compounds in the solar cells enabled conclusions to be drawn about the effects on electron injection of the HOMO energy level and the number and position of binding groups. The highest incident photon-to-current conversion efficiency (IPCE) of 4 % and overall conversion efficiency (η) of 0.09 % were obtained when 2,3:9,10-(22,92-carboxyl)benzo(b,k)-15,18,22,25-tetrakis(octyl)phthalocyaninatozinc(II) (63) was utilised as a sensitiser. This response was concluded to be due to the molecule possessing two binding groups and phthalocyanine like energy levels. When the ruthenium centred and zinc centred compounds were compared as sensitisers in DSCs, an increase in photovoltage and photocurrent was observed with the use of the ruthenium centred compounds. This is due to the binding group being attached to the axial ligand and therefore being situated closer to the LUMO electron density which is found at the centre of the molecule. As the binding group is closer there is less hindrance to electron injection into the TiO2 conduction band. Aggregation studies were also conducted on the acid and ester substituted zinc naphthalocyanine with and without the use of additives. It was found that the ester existed primarily as a dimer whose formation is concentration dependent. The acid also existed as a dimer but produced a "fake" monomer peak due to the formation of J aggregates. It was found that upon dilution the angle of the J aggregates shifted so that they formed face-to-face aggregates. It was found that the peripherally binding additive cetyltrimethylammonium bromide (CTAB) prevented aggregation at a concentration 20 times that of the compound but upon dilution rearranged itself so that aggregation was no longer inhibited.
| Identifer | oai:union.ndltd.org:ADTP/265264 |
| Date | January 2006 |
| Creators | Goddard, Victoria H. M. |
| Publisher | Queensland University of Technology |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | Copyright Victoria H. M. Goddard |
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