Charge-Compensated Doping Extends Carrier Lifetimes in SrTiO₃ by Passivating Oxygen Vacancy Defects

Experiments reported that oxygen vacancies shorten the charge carrier lifetime of SrTiO₃ but that it is greatly improved upon Al and Na doping. Using nonadiabatic (NA) molecular dynamics, we demonstrate that the in-gap hole trap state created by an oxygen vacancy can be eliminated by charge-compensated doping when two Ti⁴⁺ ions or two Sr²⁺ ions are equally replaced by Al³⁺ or Na⁺ ions. Nevertheless, Al³⁺ and Na⁺ reduce the strength of NA coupling to a different extent, resulting in increased charge carrier lifetimes of 4.6 and 1.3 ns. The lifetimes are several times longer than that of the pristine system and 3 orders of magnitude longer than that of defective SrTiO₃, which is within 50 ps due to strong NA coupling. The weakly correlated electron and hole wave functions in doped systems accelerate decoherence, further delaying charge recombination. Our study rationalizes the complex charge-phonon dynamics in SrTiO₃ and proposes charge-compensated doping for the design of advanced visible-light photocatalysts.