Computational investigations on Heteroleptic Dithiocarbimate–diamine-based metal complexes as photosensitizers in dye-sensitized solar cells

Abstract

In this work, nine heteroleptic complexes of the form [M(L)(L')] where L = p-tolylsulfonyldithiocarbimate (p-CH<inf>3</inf>C<inf>6</inf>H<inf>4</inf>SO<inf>2</inf>N=CS<inf>2</inf>2−); M = Ni (II), L' = 2,2′-bipyridine (Bpy) (C1) or 1,10-phenanthroline (Phen) (C2) or N1,N1,N2,N2-tetramethylethylenediamine (TMEDA) (C3); M = Pd (II), L' = Bpy (C4) or Phen (C5) or TMEDA (C6); and M = Pt (II), L' = Bpy (C7) or Phen (C8) or TMEDA (C9) have been theoretically investigated as sensitizer for dye-sensitized solar cells (DSSCs). The electronic structure of the dye, i.e., spectroscopic and redox properties and its interactions with the TiO<inf>2</inf> cluster, is widely elaborated and discussed by employing density functional theory (DFT) and time-dependent DFT (TD-DFT). Frontier molecular orbital and projected density of states analyses disclosed that the charge separation state was generated for C1, C2, C4, C5, C7 and C8 complexes. According to the energy level diagram, C4 would be the best sensitizer in terms of driving force for dye regeneration. The reorganization energy (Λ<inf>total</inf>) calculations showed that Bpy and Phen-based complexes had lower Λ<inf>total</inf> values, indicating that they could be used as sensitizers for better photovoltaic performance. The adsorption energy (E<inf>ads</inf>) of dye@TiO<inf>2</inf> showed that, with the exception of C3, C6, and C9 complexes, all other sensitizers had negative E<inf>ads</inf> values, indicating an efficient charge transfer between the sensitizer and TiO<inf>2</inf> cluster; and the photovoltaic and global reactivity parameters indicated that, in addition to C1 and C2, C4 and C7 would be viable sensitizers. © 2025 Elsevier B.V.