Anchoring groups for dyes in p-DSSC application: insights from DFT.

We present hybrid, periodic, spin-polarized density functional theory calculations of antiferromagnetic NiO bulk, of its clean (100) surface and of the binding on this latter of four different organic ligands, relevant for p-type dye-sensitized solar cells (p-DSSC) applications. We find evidence for a strong chemisorption of all ligands to the NiO surface in the form of short interatomic distances between surface Ni atoms and ligand atoms, confirmed by high binding energies. Although the analysis of the impact of the ligand adsorption on the density of states of the NiO substrate reveals significant modifications, the overall picture obtained is in line with the operation principles of p-DSSC in all cases. However, some of the considered ligands significantly shift the density of states to lower energies, which, in p-DSSCs employing these ligands to anchor dyes to NiO, could force the use of dyes with deeper HOMO energies and alternative redox couples capable of accepting electrons from the dye (assuming dye bandgaps in the UV/visible range).