BiSbWO₆: Band Energies Tuning of a Mixed Sb(5s)/Bi(6s) Lone-Pair-Electrons System

Post-transition metal oxides with electronic configuration ns2-md0 have been highlighted as efficient photocatalysts due to their favorable optoelectronic properties. Of the ns2-md0 class of materials, none have received greater attention than BiVO4. Due to the localized V 3d conduction orbitals, BiVO4 charge transport properties are affected by the formation of small polaronic states. Alternatively, one may consider materials with more delocalized conduction bands, such as W 5d0 compounds. One such example is the russellite mineral, or Bi2WO6. Density functional theory is used to calculate the electronic properties of Sb-alloyed Bi2WO6, and to study the effects of introducing Sb 5s orbitals to the band structure. In studying the configurational space of BiSbWO6, we provided new insights into the behavior of mixed Sb(5s)/Bi(6s) lone-pair electrons in post-transition metal oxides. We find that local distortions caused by Sb 5s lone-pair electrons indirectly lead to upshifts in both valence and conduction band edges. To isolate the role of the lone pairs, we compare the observed effects to those in a WO3 control model that is subject to structural deformations. These insights may be further extended and applied more generally to mixed post-transition metal oxides in pursuit of new efficient solar absorbing materials.