Investigation of ruthenium complexes of novel heterocyclic ligands for application in photovoltaic cells

Mohammad Nozari

doi:10.17918/00001383

Fossil fuels are a finite resource and will eventually run out. The use of fossil fuels contributes to global warming from air pollution created mainly by the greenhouse gas carbon dioxide, which encourages using other energy alternatives. Finding clean and renewable energy sources such as wind power, hydropower and photovoltaics is one of the top priorities in science. Solar energy is one of the main renewable sources being invested in, it is clean and abundant and can benefit the world. There are different types of photovoltaic cells, solar cells, such as silicon cells, thin-film cells, polymer cells, organic cell, perovskite cells, quantum dot and dye-sensitized solar cells (DSSCs) that have been widely investigated due to their high potential for solving the energy problem. DSSCs are investigated in this thesis. In this work, different classes of compounds were investigated, based on bzimpy, pyrazole, NTB in chapter 2 and dibenzo[b,j][1,10]phenanthrolines in chapter 3 which highlight the effect of having multiple groups on the dye molecule as well as the extended aromaticity, on the properties of ruthenium-based DSSCs. For bzimpy, pyrazole and NTB, first, novel ligands were designed, synthesized, and then N-alkylation method was utilized which works systematically unlike some previous methods in the literature, to insert different groups on the ligand. Dyes were synthesized using the ligands: mebzimpy, prbzimpy, npbzimpy and anbzimpy had power conversion efficiencies ([eta]) of 0.38%, 11.58%, 0.34% and 0.28% respectively. For pyrazole derivatives, Dyes were synthesized form quinolyldiphenylpyrazole and quinolyldi-t-butylpyrazole ligands had power conversion efficiencies ([eta]) of 2.14% and 0.81%, respectively. NTB-based dyes synthesized from Et₃NTB, Pr₃NTB and Np₃NTB had power conversion efficiencies ([eta]) of 0.20%, 0.28% and 0.13% respectively. For dibenzo[b,j][1,10]phenanthrolines, a synthetic scheme was developed that improves previously used methods, creating the possibility of making a library of novel compounds to be used for future investigations. These ligands were then coordinated to ruthenium, and finally ruthenium complexes (dyes) were studied and evaluated for their application in DSSCs. Phenanthroline dyes synthesized form dsdhphen, dsphen, badhphen and baphen had power conversion efficiencies ([eta]) of 0.35%, 0.46%, 0.59% and 0.52% respectively. It was found that all these dyes display extended absorption of 622 to 628 nm in comparison to the reference dye (N719) which is 533 nm. Pyrazole-based dyes had the highest overall efficiency among investigated groups. However, increasing the absorption maxima to longer wavelengths does not necessarily increase the efficiency.

Investigation of ruthenium complexes of novel heterocyclic ligands for application in photovoltaic cells

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Investigation of ruthenium complexes of novel heterocyclic ligands for application in photovoltaic cells

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