Efficient Organic Fluorescence Scintillation by Engineering Anti-Kasha Triplet Energy Levels

Scintillation, the phenomenon of luminescence under bombardment of x-rays, excites multiple areas, including ionizing radiation detection, biomedical imaging, and electron microscopy. For organic scintillators, employing triplet excitons represents a useful strategy to increase the radioluminescence intensity. However, utilization of the triplet excitons generally conflicts with the development of fast scintillators, which are key to fast-timing medical radiography. Here, we design a series of efficient fluorophores with anti-Kasha energy levels, enabling fast scintillation by effectively utilizing high-lying triplet excitons. As a result, the fluorescent scintillators exhibit short lifetimes in the nanosecond range and a low detection limit of 21.7 nGy s^-1, which is two orders of magnitude lower than the dosage for x-ray medical diagnostics. Encouraged by the results, we further employ high-throughput virtual screening to accelerate the development of fast organic scintillators and demonstrate their potential in advanced radiography. This design principle could provide inspirations to exploit efficient fast organic scintillators, thereby advancing the applications of organic scintillators in the x-ray community.