Indirect-To-Direct Band Gap Transition of One-Dimensional V₂Se₉: Theoretical Study with Dispersion Energy Correction

Recently, we synthesized a one-dimensional (1D) structure of V₂Se₉. The 1D V₂Se₉ resembles another 1D material, Nb₂Se₉, which is expected to have a direct band gap. To determine the potential applications of this material, we calculated the band structures of 1D and bulk V₂Se₉ using density functional theory by varying the number of chains and comparing their band structures and electronic properties with those of Nb₂Se₉. The results showed that a small number of V₂Se₉ chains have a direct band gap, whereas bulk V₂Se₉ possesses an indirect band gap, like Nb₂Se₉. We expect that V₂Se₉ nanowires with diameters less than ∼20 Å would have direct band gaps. This indirect-to-direct band gap transition could lead to potential optoelectronic applications for this 1D material because materials with direct band gaps can absorb photons without being disturbed by phonons.