Screening Doping Strategies to Mitigate Electron Trapping at Anatase TiO2 Surfaces.

Nanocrystalline anatase titanium dioxide is an efficient electron transport material for solar cells and photocatalysts. However, low-coordinated Ti cations at surfaces introduce low-lying Ti 3d states that can trap electrons, reducing charge mobility. Here, a number of dopants (V, Sb, Sn, Zr, and Hf) are examined to replace these low-coordinated Ti cations and reduce electron trapping in anatase crystals. V, Sb, and Sn dopants act as electron traps, while Zr and Hf dopants are found to prevent electron trapping. We also show that alkali metal dopants can be used to fill surface traps by donating electrons into the 3d states of low-coordinated Ti ions. These results provide practical guidance on the optimization of charge mobility in nanocrystalline TiO2 by doping.