Theoretical Study Of Porphyrins As Sensitizers For Dye-sensitized Solar Cells

Porphyrins have the great application potential on the sensitizer of dye-sensitized solar cells. In this work, the quantum chemistry calculations were used to study the influence of the molecular structure on the molecular performance, developing a new method to predict certain properties of target compounds. We design new molecules, which may with much better properties than the known ones as the sensitizers of dye-sensitized solar cells.This work is a part of the national natural science foundation of china (Grant No. 20501011). Some interesting and significant results were obtained in the following subjects.1. Theoretical study on tetraphenyl zinc metalloporphyrin moleculesThe molecular orbital energy levels of the tetraphenyl zinc metalloporphyrin and nine kinds of electron acceptors A-I were studied by the density functional B3LYP/6-31G (D) method, and the donor-acceptor pairs were selected as the porphyirn sensitizer candidates. And then the influences of the molecular structure and the electronic absorption spectra on the sensitizer molecular performance were investigated through calculating the molecular orbitals and the electronic absorption spectras at the density functional B3LYP/LANL2DZ level. Simultaneously, as compared with the experiment data, we find that the smaller the HOMO-LUMO molecular energy gaps, the higher light-to-electric power conversion efficiencies of the sensitizer sensitized solar cells would be. Some results were obtained according to the calculation as follows: the thought to analyze the molecular orbital energy levels of the donors and the acceptors to select the porphyrin sensitizer candidates is practical.2. Theoretical study on the substituent effect of the porphyrin moleculesDensity functional theory (DFT) calculations with 6–31G(D) basis set of porphine,eleven kinds of substituted porphyrins and nine kinds of electron acceptors were carried out to study the substituent effect on the molecular orbitals and select the appropriate donor-acceptor pairs as the sensitizer candidates. Results from the calculations show that the HOMO and LUMO levels vary systematically from low to high along the variation of the substitutents from electron-withdrawing to electron-donating. The selected candidates are very promising to challenge the current conversion efficiency record 7.1%.3. Theoretical study on the alkyne-bridged zinc tetraphenylporphyrinsThe molecular orbital energy levels of the triphenyl zinc metalloporphyrin and twenty kinds of electron acceptors A-T were studied by the density functional B3LYP/3-21G* method, and the donor-acceptor pairs were selected as the porphyirn sensitizer candidates. Some results are obtained according to the calculation as follows: the HOMO-LUMO energy gaps of part of the sensitizer candidates selected are much smaller, part of the sensitizer candidates are very promising to challenge the current conversion efficiency record 6.0% of the alkyne-bridged porphyrin sensitizers.4. Molecule design and screening of novel alkyne-bridged zinc metalloporphyrin sensitizer candidatesThe donor-acceptor combinations of diarylamino-substituted zinc porphyrin, as well as tri-4-methylphenyl-, tri-hydroxyl- and tri-amino-substituted zinc porphyrins as donors with the selected acceptors E, M, Q, R and S as novel alkyne-bridged zinc porphyrin sensitizer candidates have been designed and calculated at the density functional B3LYP level. The result shows that they are all very promising to provide good performances as sensitizers because of their smaller HOMO-LUMO energy gaps, more and red-shifted absorption bands than the compound which provide the photon-to-current conversion efficiency 6.0%. Particularly, the tri-amino-substituted zinc porphyrin sensitizer candidates are the best systems. They are all promising to challenge the current photon-to-current conversion efficiency record 6.0% of the alkyne-bridged porphyrin-sensitized solar cells.