Shorooq Alomar1
Kaust1
In recent years, X-ray imaging scintillators have garnered significant attention for their potential in real-world applications such as medical radiography, food industry, and security inspection. However, high-performance scintillators have been limited to inorganic ceramic and perovskite materials, which are known to require harsh preparation conditions, high environmental toxicity, low stability, and very high fabrication costs. Alternatively, organic scintillators, particularly thermally-activated delayed fluorescent (TADF) systems, offer efficient utilization (nearly 100%) of both singlet and triplet excitons, making them a strong contender in the scintillation market. Their stability, low toxicity, scalability, and diverse radioluminescence mechanisms also make them an excellent alternative choice to compete, even not replace ceramic and perovskite scintillators.<br/><br/>In this contribution, we successfully introduce, for the first time, a novel approach for X-ray imaging scintillators that utilizes very efficient and ultrafast energy transfer at the interface of TADF chromophores for X-ray imaging scintillators with exceptional spatial resolution. More specifically, our study showcases the successful use of efficient singlet-singlet (S-S) and triplet-triplet (T-T) energy transfer mechanisms between the TADF donor (sensitizer) and the TADF acceptor (scintillator) to achieve high-resolution imaging of up to 20 lp/mm, representing the highest resolution reported thus far for organic scintillators, and is at least two times higher than that achieved by commonly used commercial inorganic scintillators. Our results highlight a new path to improve the resolution and sensitivity of imaging by leveraging the advantages of simultaneous S-S and T-T energy transfer mechanisms that nearly completely use the absorbed X-ray energy. Our experimental findings also demonstrated the enormous potential of this energy transfer strategy in yielding high-performance organic X-ray imaging scintillators, providing a robust and cost-effective alternative for X-ray imaging applications that are free from harsh preparation conditions and significant fabrication costs.<br/><br/>We believe that these innovative TADF-based X-ray screens, with their efficient interfacial energy transfer, will not only serve as a benchmark for the fabrication of efficient organic scintillators with a simple molecular engineering strategy, but also garner significant interest from the scientific community and expand the current understanding of X-ray imaging scintillators.