Sub-bandgap trap sites for high-density photochemical electron storage in colloidal SrTiO3 nanocrystals

We report facile and reversible electron storage in colloidal SrTiO3 nanocrystals using photochemical and redox titration methods. A very high electron storage capacity (∼180 e− per 7 nm nanocrystal) is achieved which we attribute to the localized nature of added electrons at sub-bandgap trap sites in these colloidal SrTiO3 nanocrystals. The rate of electron accumulation is also found to be much faster with ethylene glycol as the sacrificial reductant compared to ethanol. This work provides key insight and establishes a kinetic bottleneck in the charge trapping processes.