Influence of structural, electronic and optical properties of boron and nitrogen doping in tetragonal PbTiO3: insight from first-principles

The structural, electronic and optical properties of intrinsic, B- and N-doped tetragonal PbTiO3 are investigated by first-principles calculations. After doping with B (N) atom, the stability of the system decreases, but it is still thermodynamically stable. B-doped (N-doped) PbTiO3 appear new B-2p (N-2p) impurity bands near Fermi level, reducing the bandwidth from 2.02eV to 0.56eV (0.43eV). Imaginary part of dielectric function has the largest peak at the photon energy of 5.81 eV, which originates from the transition of electrons from the occupied O-2p VB states to the unoccupied Ti-3d CB states. The static refractive index of B- and N-doped PbTiO3 are larger than that of PbTiO3. B-doped (N-doped) PbTiO3 can increase the light absorption capacity of near-infrared wavelengths and visible light, and energy loss in the visible light range is very small, indicating that Band N-doping are expected to improve the optical properties of PbTiO3.