Intramolecular Charge Transfer Of Two Novel Dyes With DFT

With the shortage of coal,oil and natural gas, etc, people need to find new sources of energy urgently. Solar energy is one of clean energy with no pollution that accounted for more than ninety-nine percent of total energy. The solar cell has many transformational forms and the most important form is translating solar energy into chemical energy and electrical energy. Low-cost of the solar cell and make easily open up new ways for reducing cost. The key role of dye is electronic generation and injection. Dye served as sensitizer can be excited and the excited dye send electron to titanium dioxide conduction band of semiconductor. Dye lost electron become positive ion and then is restored by electrolyte. The new sensitizer enjoy wide spectral absorption band which has decisive effect on the photoelectric conversion efficiency. From the 1970s, people focus on exploring organic compound of a large conjugate structure as dye sensitizer material. In this paper, nonmetal Organic Dye P1 (4-(bis-{4-[5-(2,2-dicyano-vinyl) thiophene-2-yl] thiophene} amino) benzoicacid) and P4 (4-{bus-[4-(2,2-dicyano-vinyl) biphenyl-4-yl] amino} benzoic acid) is studied object. P1 is conjugated chain unit compound with thiophene ring and possess good fluorescence excitation character and stability.P4 was designed by using phenyl ring (for P1) instead of thiophene.In this paper, two novel organic dyes (P1, P4) for organic solar cell were investigated by means of quantum-chemical calculations. Optimized geometries of two dyes and their ground state properties were studied at B3LYP/6-311G (d) level. The energies and densities of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), as well as the energies level differences, are shown. For HOMOâ†'LUMO transition, the energy level differences of P1 and P4 is about 2.79eV and 3.26eV, respectively. Excited-state properties of two dyes were investigated using time-dependent density functional theory (TD-DFT).In this sections, we study optical property of two dyes. We adopted 3D cube representations to directly visualize the charge transfer in vertical absorption. The orientation and strength of transition dipole moment are showed with transition density (TD).The charge difference density (CDD) revealed the orientation and results of the charge and energy transfer.