Charge-Compensated Doping Extends Carrier Lifetimes in SrTiO<sub>3</sub> by Passivating Oxygen Vacancy Defects
Cheng Cheng, Run Long
Abstract
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.