Abstract

Technological advancements have long been intertwined with material innovations. In the realm of X-ray imaging, scintillation energy donor-acceptor molecular systems hold considerable promise for enhancing scintillator performance. These systems with efficient energy transfer processes are essential for improving both X-ray absorption and light emission along with a control over excited-state dynamics, ultimately leading to superior imaging resolution. This methodology has significant implications for the design and optimization of various light conversion devices, particularly X-ray imaging scintillators.

This dissertation explores the development and enhancement of scintillator materials through the innovative application of thermally activated delayed fluorescence (TADF) chromophores. TADF chromophores facilitate delayed fluorescence via reverse intersystem crossing, thereby enabling the effective utilization of both singlet and triplet excitons. Our findings highlight significant advancements in X-ray sensitivity and radioluminescence intensity achieved through the strategic interplay between distinct TADF systems, leveraging simultaneous singlet-singlet and triplet-triplet energy transfer mechanisms. In addition to organic TADF-based scintillators, this research extends the framework to hybrid scintillators by integrating TADF materials with inorganic [ZnS(Ag)] components. This combination has yielded substantial improvements in sensitivity and spatial resolution, illustrating the synergistic benefits of hybrid material systems. Furthermore, the exploration of organometallic scintillators reveals their remarkable capabilities, offering 100% exciton utilization efficiency and unity intersystem crossing (ISC), which together enable outstanding X-ray radioluminescence performance even at low temperatures. The main goal of this dissertation is to advance scintillator materials through a synthesis of molecular engineering and innovative energy transfer strategies, ultimately enhancing X-ray imaging screen performance. To conclude, the research highlights the transformative potential of TADF molecular systems in scintillation applications, signaling a shift toward next-generation high-performance imaging technologies. It contributes to the evolution of X-ray scintillation and underscores the significance of these advancements across various applications.