Boron Cluster-Based X-Ray Scintillators for Highly Efficient Radioluminescence.

Organic scintillators represent a promising alternative to conventional inorganic scintillators; however, their practical applications are severely hampered by inferior x-ray absorption and inefficient exciton utilization, which lead to unsatisfactory scintillation performance. Herein, we designed and synthesized a novel class of highly efficient boron cluster-based organic scintillators featuring a donor-acceptor architecture, constructed by covalently integrating a carbazole donor into an iodophenyl carborane cluster acceptor. These materials exhibit high absolute quantum yields up to 95.8% and an ultralow x-ray detection limit of 76 nGy s-1, representing exceptional scintillation performance compared to the commercial inorganic BGO (Bi4Ge3O12) scintillator (105 nGy s-1). Mechanistic studies reveal that the bright radioluminescence originates from intramolecular charge transfer from the carbazole moiety to the carborane core, which leads to thermally activated delayed fluorescence (TADF) emission and enables theoretically 100% exciton utilization. This work establishes that metal-free boron clusters can serve as versatile building blocks for constructing high-performance organic scintillators, opening a new avenue for next-generation x-ray scintillators.