Atomically confined excitons in 2D perovskites for bright and sub-nanosecond scintillation

Ultrafast radiation detection is crucial for advancing medical imaging, high-energy physics, astronomy, and industrial applications, offering high spatiotemporal resolution and reduced radiation exposure. However, the bottleneck lies in the formidable challenge of achieving scintillators with both ultrafast response and high efficiency. Contrasting with previous approaches that focused on molecular-level confinement, here we propose the strategy of pushing exciton confinement to the limit of atomic scale. Using 2D perovskites as a model, we design organic A-site cations to selectively enhance in-plane distortion to localize excitons, while suppressing out-of-plane and intra-octahedral distortions to minimize the formation of inefficient, long-lived self-trapped excitons. Specifically, (1,4-CMA)PbBr₄ exhibits a rare combination of fast response (0.62 ns) and high light yield (19,700 photons MeV^-1), surpassing leading commercial and research scintillators. These properties enable breakthroughs in advanced imaging, including fast positron emission tomography with timing precision of 43.3 ps and high-resolution X-ray imaging (32 lp mm^-1).