Our ability to detect X-ray radiation and generate detailed images on internal structures in a non-destructive manner, has had profound impacts on all of our lives. Whether that is through medical imaging, allowing vital diagnosis of tumours and visualisation of broken bones; through security imaging, a vital resource for international security; manufacturing and food processing control, ensuring the food we eat is safe to eat, free from harmful objects; to scientific research, unearthing foundational principles, contributing to the progression of society. X-ray detectors are omnipresent in all our lives, contributing to our safety, health, and the progress of science and technology. To expand the potential of this crucial technology, a new generation of X-ray detector materials is required to overcome current limitations and expand performance beyond that currently achievable.

In this thesis, two families of materials with unique properties, halide perovskites and metal-organic frameworks are brought together for the first time, in a sol-gel processable, monolithic manner and utilised to advance the development of novel X-ray detector materials. Utilising the exceptional optoelectronic properties of halide perovskites, and benefitting from the enhanced stability, processability, and potential for functionalisation provided by metal-organic frameworks, a new class of X-ray detector materials are formed. Concurrently, these materials are comprehensively characterised using a suite of structural and photophysical techniques to provide mechanistic insights into their formation and photophysical processes. These crucial insights enabled the refinement and optimisation of synthesis protocols and choice of building-blocks, to enhance stability beyond previously achievable in comparable composites, and develop optimised monolithic perovskite@MOF composites tailored towards X-ray detector applications.

Overall, this thesis utilises the unique properties of perovskites and metal-organic frameworks to develop, robust, stable, and scalable X-ray detectors with outstanding promise to overcome limitations of stand-alone perovskites and current detector materials. By synergistically combining two materials, detectors with new multifunctionality are possible. We show monolithic perovskite@MOFs can play a key role in future X-ray detector devices, beyond their encapsulation and stabilisation properties, contributing to the efficient transport of X-ray stimulated charges and limiting ion migration. This work opens an array of applications and contributes to bringing perovskite-based X-ray detectors closer to commercialisation.