Theoretical Investigation on Novel Porphyrin Dyes with Functionalized Bridge and Donor Groups for Dye-Sensitized Solar Cells

A series of porphyrin dyes with functionalized bridge and donor groups are investigated as organic dyes in dye-sensitized solar cells (DSSCs) using the density functional theory (DFT) and time-dependent DFT approach. Molecular geometries, electronic structures, optical absorption spectra, and light-harvesting efficiency are analyzed in tetrahydrofuran solution. Our results show that bithiophenyl, biphenyl, and naphthyl groups on bridge decrease the HOMO-LUMO gaps and lead to obvious red shift of spectra with stronger intensities at the long wavelength region. Dithiafulvenyl, carbazolyl and naphthyl groups on donor subunit result in similar HOMO-LUMO gaps to the dye YD2-o-C8, but promote the absorption intensity significantly. The designed porphyrin dyes show better light-harvesting efficiency and coverage range along with the structural optimizations on bridge and donor groups. This theoretical investigation would facilitate the screening of the functionalized bridge and donor groups for efficient porphyrin dyes in DSSCs.