A dual heterogeneous interface enhances X-ray excited persistent luminescence (XEPL) for low-dose 3D imaging. Lanthanide-doped fluoride nanoparticles (NPs) exhibit adjustable XEPL, which is promising for 3D imaging. However, high X-ray doses and complex heating are needed for efficient XEPL. This study reports that XEPL intensity is significantly improved by constructing a dual heterogeneous interface in a double-shell nanostructure. The core@shell@shell structure passivates surface quenchers, reduces non-radiative relaxation, and lowers interfacial Frenkel defect formation energy, increasing trap concentration. A flexible film containing NPs was used to image a watch's internal structure. The findings suggest that these NPs can promote advanced X-ray activated persistent fluoride NPs and offer safer, more efficient X-ray imaging techniques. Scintillation-based X-ray imaging is used in medical diagnostics, security screening, astronomical discovery, and industrial inspection. Flexible X-ray detectors offer 3D imaging of curved or irregular objects. Lanthanide-doped fluoride NPs and halide perovskites are promising for flexible X-ray detectors. Fluoride-based core/shell nanostructures allow control of XEPL properties. A shell layer can passivate surface quenchers, enhancing XEPL intensity, while spatial separation of activators allows time-dependent color evolution. Despite progress, achieving significant XEPL brightness remains a challenge. XEPL in lanthanide-doped fluoride NPs originates from Frenkel defects after X-ray irradiation. Small NPs have a large surface-to-volume ratio, leading to Frenkel defects on the surface. A core@shell structure reduces energy migration but inhibits Frenkel defect formation. Introducing strain at the core-shell interface enhances properties like photoluminescence, catalytic activity, and magnetism. A dual heterogeneous interface reduces Frenkel defect formation energy, increasing XEPL intensity. This study shows a significant improvement in XEPL intensity by constructing a dual heterogeneous interface. The core@shell@shell structure serves two purposes: passivating surface quenchers and lowering Frenkel defect formation energy. Dy activators in Y@Lu/Gd/Dy@Y NPs showed a 40.9-fold enhancement in XEPL intensity. Similar enhancements were observed for other lanthanide activators. XEPL durations were significantly prolonged. Using Y@Lu/Gd/Tb@Y NPs in a flexible film, the internal electrical structures of a watch were imaged from five directions. A 3D reconstruction procedure enabled visualization of the stereoscopic structure. The study confirms that a heterogeneous core@shell structure enhances XEPL performance. DFT calculations show that a heterogeneous interface facilitates Frenkel defect formation. X-ray activated thermoluminescence (TL) spectra and EPR signals confirm the enhanced XEPL. The study also shows thatA dual heterogeneous interface enhances X-ray excited persistent luminescence (XEPL) for low-dose 3D imaging. Lanthanide-doped fluoride nanoparticles (NPs) exhibit adjustable XEPL, which is promising for 3D imaging. However, high X-ray doses and complex heating are needed for efficient XEPL. This study reports that XEPL intensity is significantly improved by constructing a dual heterogeneous interface in a double-shell nanostructure. The core@shell@shell structure passivates surface quenchers, reduces non-radiative relaxation, and lowers interfacial Frenkel defect formation energy, increasing trap concentration. A flexible film containing NPs was used to image a watch's internal structure. The findings suggest that these NPs can promote advanced X-ray activated persistent fluoride NPs and offer safer, more efficient X-ray imaging techniques. Scintillation-based X-ray imaging is used in medical diagnostics, security screening, astronomical discovery, and industrial inspection. Flexible X-ray detectors offer 3D imaging of curved or irregular objects. Lanthanide-doped fluoride NPs and halide perovskites are promising for flexible X-ray detectors. Fluoride-based core/shell nanostructures allow control of XEPL properties. A shell layer can passivate surface quenchers, enhancing XEPL intensity, while spatial separation of activators allows time-dependent color evolution. Despite progress, achieving significant XEPL brightness remains a challenge. XEPL in lanthanide-doped fluoride NPs originates from Frenkel defects after X-ray irradiation. Small NPs have a large surface-to-volume ratio, leading to Frenkel defects on the surface. A core@shell structure reduces energy migration but inhibits Frenkel defect formation. Introducing strain at the core-shell interface enhances properties like photoluminescence, catalytic activity, and magnetism. A dual heterogeneous interface reduces Frenkel defect formation energy, increasing XEPL intensity. This study shows a significant improvement in XEPL intensity by constructing a dual heterogeneous interface. The core@shell@shell structure serves two purposes: passivating surface quenchers and lowering Frenkel defect formation energy. Dy activators in Y@Lu/Gd/Dy@Y NPs showed a 40.9-fold enhancement in XEPL intensity. Similar enhancements were observed for other lanthanide activators. XEPL durations were significantly prolonged. Using Y@Lu/Gd/Tb@Y NPs in a flexible film, the internal electrical structures of a watch were imaged from five directions. A 3D reconstruction procedure enabled visualization of the stereoscopic structure. The study confirms that a heterogeneous core@shell structure enhances XEPL performance. DFT calculations show that a heterogeneous interface facilitates Frenkel defect formation. X-ray activated thermoluminescence (TL) spectra and EPR signals confirm the enhanced XEPL. The study also shows that