Extending the applications for lanthanide ions: Efficient emitters in short-wave infrared persistent luminescence

Trivalent lanthanide ions (Ln³⁺) have been extensively used as emitters in short-wave infrared (SWIR; 900-1700 nm) photoluminescence for many advanced applications. Herein, we report that some Ln³⁺ ions can also act as efficient emitters for SWIR persistent luminescence. Using Ca₂SnO₄ as a host, we achieved strong SWIR persistent luminescence from a group of six Ln³⁺ ions, Nd³⁺, Pr³⁺, Yb³⁺, Ho³⁺, Tm³⁺ and Er³⁺, with the emission wavelengths tunable from ∼900 nm to ∼1550 nm. A direct relationship between the depth of electron traps and the ionic radii of Ln³⁺ ions was obtained. This study greatly expands the field of persistent luminescence in the SWIR spectral region, and the Ln³⁺ ion-activated Ca₂SnO₄ SWIR persistent phosphors are expected to have promising applications in a variety of areas such as biomedical imaging and night-vision surveillance.