Accurate structural descriptor enabled screening for nitrogen and oxygen vacancy codoped TiO2 with a large bandgap narrowing

• An accurate structural descriptor to represent the doping configurations of N/V O -codoped anatase TiO 2 is constructed. • Machine learning assisted electronic properties screening for the optimal doping configurations is enabled by the structural descriptor. • Two types of doping configurations featured by a linear and corner-sharing TiO 5 N 1 /TiO 4 N 2 octahedron chain with a large bandgap narrowing are identified. • The spatial ordering of N-dopants has been uncovered as the intrinsic reason for a large bandgap narrowing in N/V O -codoped TiO 2 . Nitrogen (N) doping has been widely adopted to improve the light absorption of TiO 2 . However, the newly introduced N-2 p states are largely localized thus barely overlap with O-2 p states in the valence band of TiO 2 , resulting in a shoulder-like absorption edge. To realize an apparent overlap between N-2 p and O-2 p states, charge compensation between N 3− and O 2− via electron transfer from oxygen vacancies (V O ) to N dopants is one possible strategy. To verify this, in numerous doping configurations of N/V O -codoped anatase TiO 2 , we identified two types of V O position independent N-dopant spatial orderings by efficient screening enabled with a newly designed structural descriptor. Compared with others, these two types of the N-dopant spatial orderings are highly beneficial for charge compensation to produce an apparent overlap between N-2 p and O-2 p states, therefore achieving a large bandgap narrowing. Furthermore, the two types of the N-dopant spatial orderings can also be generalized to N/V O -codoped rutile TiO 2 for bandgap narrowing.