Energy crisis is an urgent worldwide problem today. Solar energy represents the most attractive clean energy. However, the light harvesting efficiency of current solar cells is limited. Among various efforts aiming at improving the efficiency, the development of new and effective sensitizers is of utmost significance.

This thesis deals with the design, synthesis, and evaluation of novel organic dyes for dye-sensitized solar cells, with emphasis on those with the dithiafulvene (DTF) donor. The effects of dipole moment and different subunits of the D-π-A dye molecules (side chains, donor structure, linker structure, etc.) have also been studied.

In Chapter I, a brief overview of the recent development in dye-sensitized solar cells was provided. The relevant topics, such as effect of d...[ Read more ]

Energy crisis is an urgent worldwide problem today. Solar energy represents the most attractive clean energy. However, the light harvesting efficiency of current solar cells is limited. Among various efforts aiming at improving the efficiency, the development of new and effective sensitizers is of utmost significance.

This thesis deals with the design, synthesis, and evaluation of novel organic dyes for dye-sensitized solar cells, with emphasis on those with the dithiafulvene (DTF) donor. The effects of dipole moment and different subunits of the D-π-A dye molecules (side chains, donor structure, linker structure, etc.) have also been studied.

In Chapter I, a brief overview of the recent development in dye-sensitized solar cells was provided. The relevant topics, such as effect of dipole moment and sensitizers based on DTF donors, have been reviewed.

Described in Chapter 2 were two novel sensitizers using dithienopyran (DTP) as the π-linker.The DTP unit was used as a novel π-linker in D-π-A dyes. In addition, the dipole moment effect caused by changing the DTP orientation was also studied.

In Chapter 3, the synthesis and evaluation four novel DTF-based sensitizers were presented. Electron-rich π-linker units, such as ethylenedioxythiophene (EDOT), benzodithiophene (BDT), dithienosilole (DTS), and furan, were employed. As expected, broader absorptions were observed for these dyes. Their performance in DSSCs was studied and compared. Additional experiments, such as charge extraction, were carried out to understand their performance difference.

In Chapter 4, different electron-deficient units, such as benzothiadiazole (BT) and QN (quinoxaline), were introduced as π-linkers to form D-A-π-A structures. The effect of the electron-deficient units on the absorptions and photovoltaic performance was studied.

Furthermore, three new DTF-based sensitizers with different side chains on the DTF donor unit were synthesized (Chapter 5). The effect on aggregation and charge combination by the introduction of these side chains was studied and discussed.

Overall, in this thesis work, different structure-performance studies on the new series of organic dyes bearing DTF donors for DSSCs were carried out. The results indicated that different factors of the dye structures, such as dipole moment, donors, and linkers, have complicated influence on the ultimate performance of these dyes in DSSCs. Although moderate photo-current conversion efficiencies were observed for the majority of the dyes evaluated in this thesis work, the fundamental understanding of the structure-performance relationship in dye-sensitized solar cells will ultimately contribute to the development of solar cell with better performance.