In this thesis, a series of unsymmetrical small molecules containing perylene bisdiimide (PDIs) with carboxylic acid functional group was synthesized. Benzoic acid was connected to perylene bisdiimide at 7 position to form the binding with TiO2 and electron-rich aromatic function group was connected to perylene bisdiimide at 1 position to increase electron density of perylene core. The substituent effects on the photophysical and electrochemical properties of these unsymmetrical aryl-substituted perylene diimides have been carefully studied. Because of the properities of broadening visible absorption spectrum of these molecules, we use these molecules as the dye of Dye-Sensitized Solar Cell (DSSC).