DFT/TD‐DFT Studies of Metal‐Free N‐Annulated Perylene Based Organic Sensitizers for Dye‐Sensitized Solar Cells: Is Thiophene Spacer Essential for Improving the DSSC Performance?

TLDR: In this paper, photo-physical properties of five N-annulated perylene (NP) based metal free organic D-π-A sensitizers for dye-sensitized solar cells have been investigated by using density functional theory (DFT/B3LYP/6-31G).

Abstract: In this study, photo-physical properties of five N-annulated perylene (NP) based metal free organic D-π-A (donor-π-linker-acceptor) sensitizers for dye-sensitized solar cells (DSSCs) have been investigated by using density functional theory (DFT/B3LYP/6-31G (d)). These dyes contain triphenylamine (TPA) derivative linked to the NP, thiophene and 2-cyanoacetic acid as electron donor, conjugated linker and acceptor. Effect of TPA, substituted TPA and the of linker on the highest occupied molecular orbital, lowest unoccupied molecular orbital and bandgap energy of these compounds have been calculated and compared against experimental values reported. The electronic absorption spectra of these dyes are studied by time-dependent density functional theory calculations. Based on the calculations, (E)-2-cyano-3-(10-(4-(diphenylamino) phenyl)-1-(2-ethylhexyl)-1H-phenanthro [1,10,9,8] carbazol-3-yl) acrylic acid (NPS-4) is identified as best dye for the DSSCs operating with I3−/I− containing electrolyte. Furthermore, chemical hardness and reorganization energy of the dyes have been calculated and analyzed, whose values predicted the electron injection ability of the dyes and hence short-circuit current density. Although, all five dyes were capable of injecting electron into the conduction band of TiO2, the highest driving force for dye regeneration, the lowest reorganization energy and the highest open-circuit voltage of the NPS-4 makes it most suitable for the DSSC application.