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.