Density Functional Characterization of Electronic and Optical Properties of Strontium Titanate Under Doping and Strain for Optoelectronic Applications

We perform first-principles calculations, to investigate the effect of doping of metal dopants (silver, gold, aluminum, and copper) on the electronic, structural, and optical properties of strontium titanate SrTiO
₃
. We further explore the impact of varying strains (compressive and tensile) on the optical and electronic properties of pristine and doped SrTiO
₃
. Our results suggest that the undoped SrTiO
₃
exhibit a wide bandgap of 2.94 eV with high optical absorption only in the ultraviolet (UV) region. On doping the SrTiO
₃
by metal dopants, the bandgap is significantly narrowed and most of the absorption peaks are found to shift towards the lower energies (red-shift). Subsequently, the absorption is enhanced in the visible region (∼380 to 800 nm) of the optical spectrum. The decrease in the bandgap is highest for the dopant Cu. Further, on the application of the biaxial strain (tensile and compressive) on the doped-SrTiO
₃
, the optical absorption is enhanced in the visible region, particularly for the high compressive strain of 20%. The calculated refractive index and dielectric function for all the structures of SrTiO
₃
are found to follow the trend of absorption. The enhanced absorption in the desired visible region through doping and strain may find prospective applications in the fabrication of photovoltaic, optoelectronic, and solar devices.