Directly Identifying Multiple Cr3+ Emitting Centers for Broad Near-Infrared Emission in an Efficient and Near-Zero Thermal Quenching Garnet-Type Phosphor

Cr3+ doped garnet-type (A(3)B(2)C(3)O(12)) near-infrared (NIR) phosphors is a desirable research hotspot due to their prospective night vision, bioimaging, and plant growth utilizations. Meanwhile, the origin of multisite broad emission is yet a controversial topic. To resolve the trouble, verifying accurately the multiple Cr3+ occupancy sites is a key. Furthermore, it is an urgent need for improving the external quantum efficiency and luminescent thermostability. Herein, in Y3Sc2Al3O12 (YSAO), advanced electron microscopy technique is employed to directly confirm that the obtained broadband NIR emission originates from Cr3+ in [ScO6] octahedral and [YO8] dodecahedral sites. The optimal YSAO:5%Cr3+ sample exhibits high quantum efficiency (IQE/EQE = 74/31%) and near-zero thermal quenching (97%@423 K and 92%@473 K). The theoretical calculations and experimental proofs reveal that YSAO possesses high structural rigidity and wide bandgap, which is responsible for the extremely thermostable luminescence. The high-power YSAO:5%Cr3+-converted NIR LED device shows promising multifunctional applications. This work not only provides an efficient NIR broadband phosphor with near-zero thermal quenching, but also provides an effective determination method for the multiple emitting centers of phosphor materials.