First-principles study of the effects of Hf doping and different valence state O vacancies on the optoelectronic properties of SnO2

The electronic structures of rutile-phase SnO2 with oxygen vacancies for different valence (VO0, VO1+, and VO2+) are studied using first -principles calculations. Under Sn-rich conditions, compared with VO1+, VO0,2+ shows a negative formation energy and VO2+ is the most stable. In addition, an increase in polarizability and an enhancement in visible light absorption are observed in the VO0 structure. To inhibit oxygen vacancies, the introduction of Hf ions as a dopant SnO2 is considered. Under Hf doping, the formation energy of oxygen vacancies is increased, indicating the inhibition of oxygen vacancies. Among the considered structures, Hf1Sn15O30 and Hf2Sn14O30 show the narrowest and widest bandgaps, respectively, resulting in blue shifts of the light absorption edges that extend the photoresponse range of the SnO2 material.