Oxygen vacancies (O_V's) in ceria (CeO₂) are critical structural and electronic features that underpin ceria's remarkable oxygen storage capacity, redox catalytic performance, and wide-ranging applications in catalysis, solid oxide fuel cells, and gas sensors. These vacancies, which result from the removal of oxygen atoms, enable dynamic oxygen exchange between the solid and its environment, profoundly influencing ceria's catalytic properties. The intricate surface structures of ceria play a key role in determining its properties and its interactions with supported metal catalysts. Over the past decade, advancements in state-of-the-art in situ characterizations, first-principles calculations, and emerging machine learning frameworks have significantly enhanced our understanding of the formation mechanisms, behaviors, and catalytic roles of O_V's. This perspective highlights recent experimental and theoretical progress in ceria surface research, emphasizing the dynamic interplay between surface structures and reactive environments. Additionally, the perspective addresses key challenges in elucidating ceria's defect chemistry and explores opportunities to tailor its properties using multiscale modeling and AI-driven methodologies.

Perovskite light-emitting diodes (PeLEDs) could be of use in the development of active-matrix displays. However, due to ion migration in crystal structure, PeLEDs have electroluminescence rise times over milliseconds, which is problematic for the development of high-refresh-rate displays. Here, we show that the electroluminescence rise time of PeLEDs can be reduced to microseconds using an individual-particle passivation strategy. The approach is based on BF₄⁻ ions that can passivate every nanocrystal in a perovskite emissive layer during film deposition. It leads to a defect-free film with discrete nanostructure and excellent crystallinity, which inhibits ion migration. Our strategy can be applied in perovskite nanocrystal films with different colours: red (635 nm), green (520 nm) and blue (475 nm). These PeLEDs all demonstrate response times within microseconds and high external quantum efficiencies of 22.7%, 26.2% and 18.1%, respectively. This allows us to create microsecond-response active-matrix PeLEDs that exhibit external quantum efficiencies above 20% at a display brightness of 500–3,000 cd m⁻² for green devices with a resolution of 30 pixels per inch. We also develop microsecond-response red, green and blue active-matrix displays with 90 pixels per inch.