Optoelectronic Properties of Doped CaTiO₃ (C, N, Si and P):

Abstract

This study uses density functional theory (DFT) with generalized gradient approximation (GGA) and modified Becke-Johnson potential (mBJ) to analyze the structural, electronic, and optical properties of perovskite materials, where indicates the number of dopant atoms at the oxygen (O) site. In this research, Y represents the elements C, N, Si, and P, which are substituted at oxygen sites with a doping concentration of x = 16%. Firstly, the structural optimization results reveal negative formation energies for both pure and doped CaTiO₃, confirming the stability. Moreover, doping with Y significantly reduces the bandgap energy compared to undoped CaTiO₃ (2.766 eV). Specifically, the band gaps for materials (Y = C, N, Si, and P) are reduced to 0.87, 1.63, 0, and 0.6 eV respectively. In addition, doping with C and N retains the nature of the indirect band gap, with electronic transitions between the Γ and L points of the Brillouin zone, whereas doping with P results in a direct band gap. Additionally, doping with Si reduces the band gap to zero, resulting in metallic behavior. Furthermore, the Fermi level (EF) shifts towards the valence band (VB), indicating p-type semiconductor behavior for the doped systems, except , which exhibits metallic behavior. Finally, analysis of the optical properties shows that doping increases the static dielectric constant, ε₁(0), with specific values for each dopant 7.1 for , 6.72 for , 36.63 for , and 23.69 for . Notably, doping CaTiO₃ with 16% of Y reduces the bandgap, improving optical absorption and conductivity in the visible range, making (Y= C, N, Si, and P) a promising material for photovoltaic cells and optoelectronic applications.