Manipulating\nOxygen Vacancies in γ‑Ga<sub>2</sub>O<sub>3</sub> Nanocrystals:\nCorrelation between Defect Location,\nCharge State, and Photophysical Properties

Recent advancements in colloidal synthesis have enabled\nprecise\ncontrol of extrinsic dopants in semiconductor nanocrystals (NCs),\nenriching our understanding of dopant–exciton interactions\nand opening new avenues for controlling NC properties. However, the\nmanipulation of intrinsic defects in colloidal NCs remains challenging.\nHere, we demonstrate regulation of oxygen vacancy concentration and\nlocation in γ-Ga<sub>2</sub>O<sub>3</sub> NCs, significantly\naltering their photoluminescent properties. Spectroscopic analysis\nand density functional theory calculations reveal that bulk oxygen\nvacancies are mostly neutral and lead to the formation of a deep donor\nband that contributes to the UV emission. Conversely, surface-proximate\noxygen vacancies, influenced by the band bending effect, exhibit a\ntendency toward double ionization, giving rise to the characteristic\ndonor–acceptor pair emission. This work highlights the correlation\nbetween the oxygen vacancy location and charge states, leading to\ndiverse defective states and distinct photophysical processes. Precise\ndefect manipulation offers new insights into structure–property\nrelationships and the design of functional nanomaterials.