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 ZnPcLNH2, ZnPcLNHCH3, ZnPcLN(CH3)2, ZnPcLNHPh and ZnPcLN(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.

Graphical abstractNine 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 andN(Ph)2 substituents as donors and a carboxyl group as acceptor. They were studied and compared to TT1 using DFT and TDDFT calculations at B3LYP level using LANL2DZ basis set. The novel candidates bearing the NH2, NHCH3, N(CH3)2, NHPh and N(Ph)2 moieties as donors are found very promising to provide much 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 comparing to those of TT1. The new absorption bands emerged in the 450–600 nm region may promote them from near infrared to panchromatic sensitizers.Figure optionsDownload full-size imageDownload high-quality image (204 K)Download as PowerPoint slideHighlights► Some candidates have higher LUMO levels and smaller energy gaps than TT1 and PcS6. ► Some new absorption bands emerged in the 450–600 nm region. ► The candidates are promising to challenge the efficiency records of TT1 and PcS6.