First-principles calculations for hydrogenation of acceptor defects in Li-doped SnO2

The lowering of the formation energy of tin vacancy (V-Sn) in SnO2 was suggested by hydrogenation or doping lithium to substitute tin sites (Li-Sn). Based on first-principles calculations, we report the atomic structures of hydrogen-related V-Sn and Li-Sn complexes with the number of passivating hydrogen atoms in the range from one to four. We show that the complexes are stable in structures and lower than the isolated defects in the formation energies. The degree of stability of hydrogen and lithium in hydrogen-related Li-Sn complexes is close and is enhanced with only one passivating hydrogen atom, but is reduced in the presence of more passivating hydrogen atoms. We also show that there are some stretch-mode vibrational frequencies of O-H bonds in the complexes that are lower than that of isolated interstitial hydrogen. The lowering of the frequencies is possibly related to strong secondary bonds between hydrogen and non-passivated oxygen atoms around acceptor defects, which could support a signature for the experimental identification of these complexes.