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

Abstract

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.