Theoretical study of YD2-o-C8-based derivatives as promising sensitizers for dye-sensitized solar cells

Abstract

To screen efficient sensitizers for dye-sensitized solar cells (DSSCs), two series of porphyrin sensitizers have been reengineered based on one of the best sensitizers YD2-o-C8 by introducing different heterocycles into acceptor part to form stronger acceptors. The electronic structures and optical properties of these sensitizers have been investigated using density functional theory and its time-dependent density functional theory version. The computational results suggest that the stronger acceptor can result in a narrower HOMO–LUMO energy gap, an obvious red-shift and stronger absorption in long-wavelength region compared with YD2-o-C8. Meanwhile, the analyses of electron density difference plots suggest that all designed sensitizers possess longer electron transfer distance, larger fraction of electron exchange, and smaller overlap between the zones of density depletion and increment than these of YD2-o-C8, indicating enhanced electron transfer ability from donor to acceptor groups. Moreover, the designed dyes exhibit good performance in terms of the electron injection ability, the excited state lifetime, and the strength of the interaction between dye and the TiO2 surface. As a whole, all the designed dyes, especially P4 and P6 may act as excellent sensitizers for high-efficiency DSSCs.