A DFT plus U approach to doped SrTiO3 for solar harvesting applications

We present a Hubbard U optimized density functional theory based study of band gap engineered doped SrTiO3 suitable for light sensitive applications. We tune the Hubbard U parameter U-opt to match the experimental direct band gap of SrTiO3. We benchmarked the DFT+U(op)t derived density of states, band structure and optical properties with that of sophisticated Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional simulations. The reliability of the DFT+U method is further tested in simulating stability of the cubic SrTiO3 from elastic tensor and density functional perturbation theory based phonon band structure calculations. Moreover, the DFT+U-opt simulated SrTiO3 Raman peaks are identified against the experimental observations found in existing literature. We red shift the energy band gap of SrTiO3 within the DFT+U-opt formalism from ultraviolet to visible range by incorporating different dopants such as Pt, S and Se which is consistent with recent HSE06 hybrid functional based simulations found elsewhere. The optical absorption simulations revealed steep absorption edges of doped SrTiO3 in the visible spectrum. Overall, the DFT+U approach successfully probed the potential of doped SrTiO3 in solar harvesting applications.