Interplay of oxygen vacancies and lanthanide emitters enables reversible upconversion switching
Xiaofei Yang
Nature Communications, Published online: 16 May 2026; doi:10.1038/s41467-026-73187-w Here, the authors show that the interplay of oxygen vacancies and erbium emitters in bismuth oxyhalides enables reversible, high-contrast switching of upconversion emission, offering a new strategy for high-level anticounterfeiting.