The Design, Preparation And Investigation On Photovoltaic Properties Of Phenothiazine Dyes

One of the greatest challenges which the scientific community is facing now is to meet the growing global demand for energy. Solar energy as the new clean energy meets the requirements of sustainable development for energy. Dye-sensitized solar cell(DSSC), which developed by Swiss scientist Gr?tzel on the basis of O’Regan in 1991, occupies an irreplaceable position in the field of solar cell with its advantages of environment friendly, the structure could be varied, long electron lifetime and so on. Since then, researchers are constantly focus on the optimization of each parts of DSSCs to improve the photovoltaic performances. Up to now, the conversion efficiency has reached 13%. In this thesis, we are focus on the investigations of the dyes in DSSCs.1. Explore the effects of fine changes in the structure of the dyes on the cell’s performances. Most of the dyes are characterized as donor-π- acceptor(D-π-A). In such structure, the donor group can not only affect the absorption spectrum, but adjust the levels of the dyes. Small changes in the geometry of the donor may lead to interesting photophysical and electrochemical properties. In order to study the impacts of small changes in structure of electron donor group on the properties of dyes, we designed and prepared three dyes with triphenylamine, carbazole and phenothiazine unit as electron donor, indole as bridge unit and cyanoacetic acid as electron acceptor. The results show that, for this type of dye, cell based on dye WY2 with phenothiazine as electron donor shows the best photovoltaic performances. This also paves the way for the follow-up works. Therefore, follow-up studies are all based on the content of dyes with phenothiazine unit as donor.2. Investigate the impacts of auxiliary electron donor on cell’s performances. The absorption range of simple D-π-A phenothiazine dye is relatively narrow, which would lead to the related cells can’t take full use of the light. Therefore, we introduced the auxiliary electron donor to enhance the dye’s electron-donating ability. Dye WY5 and WY6 were prepared by introducing benzil-based secondary electrons. The introduction of the auxiliary electron donor results in the red-shifted and broadened absorption spectrum. It is for this reason, the Jsc of the cells based on dye WY5 and WY6 increased and the corresponding η enhanced from 4.24 to 5.52%.3. Study the impacts of solvent effects and co-sensitization effects on the cell’s performances. Dye sensitized in different solvents would affect the aggregations and the adsorption modes on TiO2 surface and futher affect the photovoltaic performances of related cells. The aim of study on solvent effect is to investigate the impacts of diffirent sensitized solvents on the cell’s performances and further to screen the best suitable sensitized solvent for dye WY5. In addition, we used WY5 and N719 co-sensitized on TiO2 film to study the effects of co-sensitized on the cell’s performances. The investigation results show that co-sensitization achieved the panchromatic response. This directly results in the enhanced light absorption capacity and the improved photovotaic performance.