Investigating structural, morphological, electronic, and optical properties of SnO2 and Al-doped SnO2: A combined DFT calculation and experimental study

Abstract

In this study, SnO2 and Al doped SnO2 were prepared via an easy sol gel procedure, the characteristics related to structural, morphological, electronic and optical properties of tin dioxide (SnO2) doped with aluminum were investigated across various concentration (4.16 %, 2.08 %, 0 %) are reported using first-principles calculations based on density functional theory (DFT) and Boltzmann transport theory. SEM revealed spherical nanoparticles with mild agglomeration. EDX confirmed uniform composition. XRD indicated a tetragonal crystal structure, and Al doping caused lattice distortion. Optical transmittance was high in the visible range with efficient UV cut-off. Ab-initio computations were conducted, comparing the Perdew, Burke, and Ernzerhof generalized gradient (PBE-GGA) approach with the Tran-Blaha Modified Becke-Johnson (TB-mBJ) approximation. These calculations were used to determine the band structure, density of states, reflectivity, absorption coefficient, transmittance, refractive index, and extinction coefficient. The computed band structure and density of states (DOS) illustrate that the aluminum (Al) atom serves as a prevalent acceptor in SnO2, it diminishes the band gap of this material from 3.23 eV for undoped SnO2 to 3.15 eV for Al (2 %) doped SnO2, the Fermi level shifts to the valence band and the material exhibits a p-type semiconductor type. The optical characteristics reveal that with the rise in aluminum concentration, transparency improves, and the absorption spectrum displays a notable blue shift. Additionally, high static values of the dielectric constant and refractive index, along with low reflectivity, have been observed in the visible region.