First-principles investigation on structural and photoelectric properties of (Nb, Ta) codoped anatase TiO2

The structural and photoelectric properties of (Nb, Ta) codoped anatase TiO2 were studied by first-principles calculations based on density functional theory and the Hubbard U correction. The results demonstrated that hybridized states composed of Ta 5d and Nb 4d orbitals at the bottom of the conduction band enabled the Fermi level to enter the conduction band and facilitated (Nb, Ta) codoped anatase TiO2 to exhibit n-type metallic characteristics, and the conductivity of Ti-0.Nb-875(0).0625Ta0.0625O2(I) is approximately 3.2 times that of Ti-0.Nb-9375(0).O-0625(2). Noted that both conductivity and mobility decreased with the increase of the distance between impurity Nb and Ta atoms and the Nb doping concentration. Moreover, the calculated results of optical properties presented the shifts of the absorption edges towards the ultraviolet region, and (Nb, Ta) codoped anatase TiO2 possessed the high transmittance thanks to its low absorption and reflection of visible light.