New insights into assessing the favorable co-doping dopants with various co-doped cases for the band gap engineering of SrTiO3

• An evaluation method with three basic rules for assessing the favorable co-doped dopants for SrTiO3 has been proposed.
• The donor–acceptor pairs co-doping and hole–hole mediated coupling co-doping cases in SrTiO3 are studied systematically.
• The relationship between the A–O, B–O and O1–O2 three basic selection doping sites and the doping effects are studied.
• Based on the proposed evaluation method, the La–N, Ta–N and N–N co-doped systems are studied.

Density functional calculations have been performed systematically on the electronic structure, the defect formation energy, the crystal structure change and the relative binding energies for the co-doped system of SrTiO3. The La–N, Ta–N and N–N co-doped systems are chosen to simulation the A-O, B–O and O1–O2 three basic selection doping sites for donor–acceptor pairs co-doping and hole–hole mediated coupling co-doping cases in SrTiO3. An evaluation method with three basic rules for assessing the favorable co-doped dopants for SrTiO3 has been proposed and the favorable co-doping dopant with which is easy to prepare, with high structural stability and high photocatalytic activity among the different types of co-doping on SrTiO3 can be obtained. Our results offer a new path for assessing the favorable co-doping dopants for the band gap engineering of wide band gap semiconductors with different co-doping cases for hydrogen generation.