|M.Sc Thesis||Department of Chemistry|
|Supervisor:||Prof. Gross Zeev|
|Full Thesis text - in Hebrew|
Corroles are macrocyclic compounds that have not been systematically investigated with regard to the search for new compounds that may be useful as dyes for DCCS. One series of compounds prepared within this thesis is composed of corroles with different aryl groups for examination of how their electron withdrawing or pushing capability might affect efficiency. The aryl groups (three per corrole, located at the 3 meso-C-atoms) were pentafluorophenyl - very strong electron withdrawing, 2,6-difluorophenyl - less electron withdrawing and para-methoxyphenyl - electron pushing, while all had two cyanoacetic-acid binding groups on the corrole skeleton. A great difference in the total conversion efficiency has been observed: from 1.05% for the corrole with 2,6-difluorophenyl groups to 0.49% and 0.23% for these with pentafluorophenyl and para-methoxyphenyl, respectively.
The second series of corroles (all containing 5,10,15- 2,6-difluorophenyl groups) was prepared in order to examine the effect of different TiO2-binding groups (mono-cyanoacetic acid, mono-dicarboxylic acid and bis-cyanoacetic acid on the corrole skeleton), on the dye's efficiency. Surprisingly, the bis substituted corrole provided the worst results with 1.05% of total conversion efficiency as opposed to 1.74% and 1.95% of the mono-dicarboxylic acid and the mono-cyanoacetic acid, respectively.
Experiments for cell optimization were carried out by treatments intended to prevent possible aggregation of the dye. For eliminating possible π stacking aggregation, which may have a negative influence on the light harvesting efficiency of the electrode, the electrode was dipped in ethanol in order to break the intermolecular bonds. It was observed however, that overnight dipping of the electrode in ethanol led to decreased cell performance.
The second type of aggregation may be referred to as an "over occupation" of the dye on the semi-conductor surface, as in this situation it is possible that the electron injection from the dye to the semi-conductor will be badly affected. The adopted treatment for preventing this type of aggregation was to adsorb on the semi-conductor surface chenodeoxycholic acid that could serve as a spacer between the dye molecules. Results showed that the cell that contained the electrode with the chenodeoxycholic acid displayed better performance than the original cell, by 25%.
This work revealed some optimal requirements for good performance of corroles in DSSC: medium electron withdrawing effect of meso-aryl substituent, mono-cyanoacetic acid as TiO2-binding group, and chenodeoxycholic acid as spacer.