Defect‐Controlled Photo‐Thermo‐Mechanical Responsive Luminescence in Self‐Activated Phosphor

Different from traditional stimuli luminescence, defect‐controlled smart multi‐stimuli‐responsive luminescent (MRL) materials have broad application value in imaging, sensing, and medicine fields. The defect‐controlled characteristics that respond to multiple external stimuli via the different luminescent paths make it attractive in emerging multi‐response intelligent platforms, but the fundamental mechanisms underlying defect‐controlled MRL remain poorly understood and have been scarcely investigated. Based on previous research, we reported a photo‐thermo‐mechanical responsive phosphor by lanthanide ion modulated self‐activated garnet host. The garnet‐type structure can provide more excellent defect tolerance to accommodate multiple luminescent centers. The properties of self‐activated luminescence enable defects within the material to be clearly identified. Lanthanide doping not only provides more abundant luminescent modes but also enhances MRL, attributed to the synergistic effect between defects. The spatiotemporal changes of dynamic multicolor luminescence are further realized by tuning the lanthanide luminescence. Optical experiment and theoretical calculation reveal that the formation of a defect state promotes the electron transfer to the luminescence center. The defect types in MRL are homologous, with the only difference being the stimuli methods (thermo‐, photo‐, and mechano‐) and the charge carrier release rate. Proof‐of‐concept 3D delayed imaging and optical fiber sensing are demonstrated. This finding comprehensively summarizes the MRL material design principles, structure‐performance‐application relationship between lanthanide ion luminescence and defect.