Substituent effect on the meso-substituted porphyrins: theoretical screening of sensitizer candidates for dye-sensitized solar cells.

According to the concepts of attribute axis and attribute coordinate system, porphine and 11 kinds of bridge carbon substituted porphyrins as donors and 9 common acceptors A-I have been designed and calculated at the density functional B3LYP level. The substituent effects on the molecular orbital energy levels of the porphyrin derivatives have been discussed and promising donor-acceptor combinations are screened. Several novel zinc metalloporphyrins selected were then calculated by means of the DFT/TDDFT method in THF solvent. The electronic and spectroscopic properties of ZnTPP and the selected novel zinc porphyrin complexes have been investigated as solar cell sensitizers. The results show that the candidates selected are very promising to provide good performances as sensitizers, in which ZnTPPG is promising to challenge the current photo-electric conversion efficiency record 7.1% of porphyrin-sensitized solar cells. The concepts of attribute axis and attribute coordinate system are shown very helpful for tuning the molecular properties and the rational design of functional molecules with anticipated good properties.