Effect of skeleton conformation on the electronic structure of 50% Ti substituted polysilanes from density functional calculations

•We study the band structure of Ti substituted polysilane in various conformations.•Titanium substitution decreases bandgap in trans-planar conformation.•The increase in torsion angle leads to higher bandgaps.•The increases in bandgap in polysilane and polytitasilane have different origins.•Electrons from 3d-Ti orbital dominate the frontier states in polytitasilane.

We study the effect of skeleton conformations on the electronic structure of polysilanes and polysilanes with 50% Ti substitution (polytitasilanes) using first principle calculations. Various conformations including a trans-planar and a helical geometry of the skeleton backbone are examined. We found that in all cases, as the skeleton backbone is twisted away from being trans-planar, the bandgap increases. The overall band structures also exhibit some differences between the planar and helical configurations. The density of states shows that as Ti atoms are incorporated into the silane systems, the frontier state narrows indicating that the Ti substitution plays a major role at the lowest unoccupied conduction band and the highest occupied valance band. In addition, the backbone conformation has a strong influence on the bandgap and the frontier state for polytitasilanes which is not as apparent in the polysilanes.