Synthesis And Photovoltaic Properties Of Triphenylamine-and Hydrazone-based Organic Dyes

Renewable resources are one of the indispensable sources of energy in the futuresociety, which includes solar energy, wind energy, hydraulic power, and tidal energy.With the advantages of its boundlessness and clean without pollution, solar energyhas received more and more attention. The solar cells are the equipment to convertsolar energy into electrical energy by use of photovoltaic effect. Relative toconventional inorganic solar cells, dye-sensitized solar cells (DSSCs) have attractedmuch attention for their high efficiency, cheap and easily obtained. In view of thelimitations associated with ruthenium dyes, metal-free organic dyes has become oneof the candidate material for application in DSSCs, due to they have a high molarabsorption coefficient and can be prepared more easily and economically. In thisdissertation, we have designed and synthesized a series of novel triphenylamine-andhydrazones-based metal-free organic dyes, and investigated their photophysical andelectrochemical properties, especially for their photovoltaic performance of DSSCsbased on these new dyes. The main contents and results are as follows:1. Three new D-A′-π-A type triphenylamine-based dyes, Dye1, Dye2, and Dye3, with cyanoacrylic acid or malononitrile moiety as A, fluorenone or9-(dicyanomethylene)fluorene as A’, and3-hexylthiophene as the conjugated π-bridge,have been designed and synthesized. The photophysical and electrochemicalproperties of the dyes have been ivestigated by UV-visible absorption spectroscopyand cyclic voltammetry. Moreover, an emphasis of the research is the effect of theintensity of A and A’ on the photovoltaic performance of DSSCs. Results indicate thatthe electron-withdrawing ability of A’(e.g.9-(dicyanomethylene)fluorine instead offluorenone) is too strong to the effective transfer of electrons between the D and A,that is unfavorable to the improvement of the photovoltaic performance. The highestPCE value of5.33%was obtained based on Dye1sensitized solar cells (Jsc=13.39mA/cm2, Voc=0.66V, FF=0.60).2. Three new D-π-A type hydrazone-based dyes, HON, HTz, and HTzN, with3,4-bis(octyloxy)thiophene or2,5-bis(3,4-bis(octyloxy)thiophen-2-yl)thiazolo[5,4-d]thiazole as the conjugated π-bridge, cyanoacrylic acid or4-nitrophenylacetonitrilegroup as the A have been designed and synthesized. The influences of4-nitrophenylacetonitrile group on the photophysical, electrochemical and photovoltaic properties of the dyes have been invesigated in detail. Our resultsshowed that the dye HTz could adsorb on the TiO2film better than other two dyes dueto the cyanoacetic acid as an anchored group. DSSCs based on these dyes werefabricated and the photovoltaic performances were invesitaged. HTz gave the highestPCE up to5.89%(Jsc=14.87mA/cm2, Voc=0.62V, FF=0.64) among the three dyes. Inaddition, we have preliminary study the photovoltaic performance of the dyes using inbulk heterojunction-type photovoltaic devices, where HTzN dye containing4-nitrophenylacetonitrile group present the best photovoltaic properties with a PCE of0.92%(Jsc=2.96mA/cm2, Voc=0.79V, FF=0.40).