Metallophthalocyanine and Metallophthalocyanine-fullerene complexes as potential dye sensitizers for solar cells DFT and TD-DFT calculations

Abstract

The geometries, electronic structures, polarizabilities and hyperpolarizabilities, and UV-vis spectra of metallophthalocyanine dyes and metallophthalocyanine-fullerene supramolecules are investigated by using density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. The results reveal that the metal and the tertiary butyl groups of the dyes are electron donors, and the phthalocyanine rings are electron acceptors. The electron donating power of (La) is significantly greater than that of (Sc). For dyes, the highest occupied molecular orbitals (HOMOs) are π orbitals localized over the phthalocyanine rings, away from the tertiary butyl groups, and the lowest unoccupied molecular orbitals (LUMOs) are π orbitals localized over the central metal atoms. The HOMOs of the dyes fall within the (TiO2)60 and Ti38O76 band gaps, and support the issue of typical interfacial electron transfer reaction. The resulting potential drop of the supramolecule LaPc.C60 increases by ca. 22.86% under the effect of the tertiary butyl groups. This significant increase in the potential drop indicates that the tertiary butyl complexes could be a better choice for the robust operation of the molecular rectifiers. The introduction of metal atom and tertiary butyl groups to the phthalocyanine moiety leads to a stronger response to the external electric field, and induces higher photo-to-current conversion efficiency. This also shifts the absorption in the dyes and makes them potential candidates for harvesting light in the entire visible and near IR region for photovoltaic applications. It is also observed that the high spin state complex Sc(4)Pc could not be a potential candidate for harvesting light in the former region of spectrum. © 2012 Elsevier B.V. All rights reserved.