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

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.