Theoretical screening of -NH2-, -OH-, -CH3-, -F-, and -SH-substituted porphyrins as sensitizer candidates for dye-sensitized solar cells.

Following former studies, the donor-acceptor combinations of -NH(2)-substituted porphyrin donor and the acceptors C, D, E, F, H and G, those of -OH-, -CH(3)- and -Ph-substituted porphyrins as well as porphine donors and the acceptors E, G, and H, and those of -F- and -SH-substituted porphyrin donors and the acceptor G as novel sensitizer candidates have been designed and calculated at the density functional B3LYP level. The result shows that -NH(2)-, -OH- and -CH(3)-substituted porphyrins as donors combined with the acceptor G are very promising to provide good performances as sensitizers because of their smaller HOMO-LUMO gaps, much red-shifted absorption bands, and good frontier molecular orbital spatial distributions. They are all promising to challenge the current photon-to-current conversion efficiency record 7.1% of porphyrin-sensitized solar cells in which the -NH(2)-substituted porphyrins as donors combined with the acceptor G are the best systems.

Substituent effects on zinc phthalocyanine derivatives: a theoretical calculation and screening of sensitizer candidates for dye-sensitized solar cells.

A series of unsymmetrical phthalocyanine sensitizer candidates with different donor and acceptor substituents, namely ZnPcBPh, ZnPcBOPh, ZnPcBtBu, ZnPcBN(Ph)2, ZnPcBNHPh, ZnPcBNH2, ZnPcBNHCH3 and ZnPcBN(CH3)2, were designed and calculated using density functional theory (DFT) and time-dependent DFT calculations. The molecular orbital energy levels, the molecular orbital spatial distributions and the electronic absorption spectra of the ZnPcB series molecules were compared with those of TT7 and TT8 to reveal the substituent effects of different donor and acceptor groups on the phthalocyanine compounds and select good sesitizer candidates. The results show that some of these compounds have considerably smaller orbital energy gaps, red-shifted absorption bands and better charge-separated states, causing them to absorb photons in the lower energy region. Several new absorption bands emerge in the 400-600 nm region, which makes it possible for them to become panchromatic sensitizers. This characteristic is superior to the phthalocyanine sensitizers reported previously, including the current record holder, PcS6. The sensitizer candidates screened in the current work are very promising for providing good performance and might even challenge the photon-to-electricity conversion efficiency record of 4.6% for phthalocyanine sensitizers.

Theoretical design and screening of panchromatic phthalocyanine sensitizers derived from TT1 for dye-sensitized solar cells.

Computational screening of new dyes is becoming an extremely powerful tool, especially when associated with experimental synthetic efforts that might eventually lead to new and more efficient products. Nine novel unsymmetrical zinc phthalocyanine complexes derived from TT1 were designed as sensitizer candidates for dye-sensitized solar cells with three peripheral -CH3, -OH, -OCH3, -OPh, -NH2, -NHCH3, -N(CH3)2, -NHPh and -N(Ph)2 substituents as the donors and a carboxyl group as the acceptor. The molecular orbital and the electronic absorption spectra properties of these compounds were studied and compared to those of TT1 using the density functional theory and time-dependent density functional theory calculations at B3LYP level with the LANL2DZ basis set. The novel candidates bearing the -NH2, -NHCH3, -N(CH3)2, -NHPh and -N(Ph)2 moieties as the donors were found to be very promising for providing higher efficiencies than that of TT1 or even the current 4.6% efficiency record held by PcS6. They have higher LUMO levels, smaller energy gaps and red-shifted absorption bands compared to those of TT1. The new absorption bands emerging in 450-600 nm regions may promote ZnPcL-NH2, ZnPcL-NHCH3, ZnPcL-N(CH3)2, ZnPcL-NHPh and ZnPcL-N(Ph)2 from near infrared to panchromatic sensitizers. Further experimental synthetic efforts are in progress in our group to validate the predictions in this report.

Theoretical study on the electronic absorption spectra and molecular orbitals of ten novel ruthenium sensitizers derived from N3 and K8.

Ten novel sensitizer candidates Ru2, Ru4, Ru5, Ru6, Ru7, Ru8, Ru9, Ru10, Ru11 and Ru12 derived from the sensitizers N3 and K8 were designed and studied using the density functional theory and time-dependent density functional theory calculations. The influences of the C=C double bonds between the carboxyl groups and the bipyridine ring as well as the numbers and positions of the -CN groups adjacent to the carboxyl groups on the properties of the sensitizer candidates were discussed. The energy levels and the spatial distributions of the frontier molecular orbitals as well as the electronic absorption spectra of these complexes were compared with those of N3 and K8. Ru10 and Ru7 were found promising to provide superior photon-to-current conversion efficiency to those of N3 and K8 in ruthenium complex sensitized solar cells.