Research progress on perovskite nanocrystal X-ray detectors

X-rays are high-energy electromagnetic radiation with wavelengths between 10 nm and 10 pm. They are important technical supports in fields like industrial non-destructive testing, medical CT imaging, and space radiation detection. Conventional X-ray detectors have been widely deployed but still face inherent limitations. Indirect detectors, typically based on scintillators such as CsI:Tl, NaI:Tl, and Bi4Ge3O12, benefit from mature fabrication yet suffer from long afterglow, hygroscopicity, low light yield, or poor spectral matching, which restrict their performance in high-resolution and fast imaging. Direct detectors employing semiconductors like α-Se, HgI2, and CdZnTe provide high sensitivity and low detection limits but are constrained by limited carrier transport, material toxicity, high cost, and challenges in large-area fabrication, making it difficult to balance performance with scalability. In recent years, halide perovskite nanocrystals (PeNCs) have become key materials to break traditional bottlenecks. This is because they have a high X-ray attenuation coefficient, tunable band structure, and can be processed in solutions. Thanks to PeNCs’ unique size confinement effect, they show higher light yield and fast luminescence decay lifetime in radiation detection. Their large Stokes shift eases the self-absorption problem that is common in single-crystal and thin-film systems. This paper systematically reviews recent research progress of PeNCs in X-ray detection, based on the two working modes of X-ray detectors (indirect and direct detection). First, it introduces the basic principles of detectors and the structural characteristics of PeNCs. Then, it focuses on the key issues of PeNCs in indirect detection. As scintillators, their performance is mainly limited by the self-absorption effect and environmental stability. To solve these problems, researchers have used strategies like molecular sensitization, matrix encapsulation, ion doping, and composite structure design. These methods effectively reduce the self-absorption effect, significantly improve light yield and material stability, and thus achieve excellent detection performance with low detection limit and high spatial resolution. In the field of direct detection, strategies such as defect passivation and confined assembly have effectively alleviated the problems of insufficient sensitivity and excessive dark current in nanocrystal devices. Although their direct conversion performance for ionizing radiation has not yet reached the level of bulk materials, perovskite nanocrystals have unique advantages in device processing and structural design. Their good solution processability helps realize composite integration with various functional materials. The controllable preparation of uniform and dense thin films improves device stability and reproducibility. Low-cost deposition processes like printing lay the foundation for their compatibility with photodetector arrays. Overall, the primary challenge for further commercialization of PeNCs is service stability. In indirect detection, although existing PeNCs scintillators have higher light yield than traditional materials, how to effectively suppress non-radiative recombination and self-absorption to approach the theoretical limit of light yield remains a core issue for improving scintillation performance. In direct detection, it is necessary to balance film thickness and structural integrity. It is important to ensure sufficient X-ray absorption capacity while avoiding cracks and stress accumulation caused by excessive thickness. Meanwhile, further optimizing charge transport efficiency is also a key factor to promote breakthrough applications of PeNCs in direct detection.