Stretchable TADF Scintillators for High‐Resolution X‐Ray Imaging via Reabsorption Suppression

ABSTRACT Organic scintillators hold great promise for next‐generation x‐ray detection due to the potential for mechanical flexibility and low‐cost processability. However, their practical application is severely hindered by inefficient triplet exciton utilization and severe self‐absorption caused by small Stokes shifts. Here, we present a flexible organic scintillator film (DMAc‐TRZ@PDMS) that simultaneously addresses these limitations through the integration of a thermally activated delayed fluorescence (TADF) emitter into a crosslinked polydimethylsiloxane (PDMS) matrix. The composite exploits a large Stokes shift to eliminate spectral overlap, effectively suppressing reabsorption losses during photon propagation. Meanwhile, efficient reverse intersystem crossing (RISC) enables effective triplet exciton harvesting. The resulting scintillator exhibits a linear x‐ray response with an ultralow detection limit of 69.19 nGy s −1 . Benefiting from the elastomeric PDMS network, the film achieves outstanding mechanical flexibility and stable emission under deformation. Notably, the scintillator delivers a high spatial resolution of 22.9 lp mm −1 for organic‐based systems, enabling high‐resolution, nondestructive x‐ray imaging of microstructured objects with exceptional contrast. This work establishes a rational strategy to overcome the fundamental limitations of organic scintillators by combining TADF photophysics with soft‐matter engineering.