Effect of oxygen vacancy and Al-doping on the electronic and optical properties in SnO2

Abstract The electronic and optical properties of Al-doped SnO 2 without and with O vacancies are investigated by means of first-principles calculations. Our results indicate that Al-doped SnO 2 is of p-type conductivity character and its band gap decreases compared with undoped SnO 2 . The accompanied oxygen vacancies can introduce localized gap states below the bottom of the conduction band and lead to the conductivity character translating to n-type from p-type in Al-doped SnO 2 . The localized gap states are contributed by the hybridizing of Sn 5s, 5p, O 2p, and Al 3p states and the density of these states becomes much stronger with oxygen vacancies increasing. Meanwhile, Fermi level shifts upward, showing a stronger n-type conductive character. With respect to the optical properties, Al-doped SnO 2 has a weak absorption peak at about 2.73 eV in the visible region, while the presence of oxygen vacancies reinforces the absorption in the visible light region.