Detection technology capable of creating sharp images from ultra-low doses of X-rays could improve the safety of medical X-ray imaging. Invention achieves high sensitivity using novel single crystal arrangement perovskite as X-ray detection materials.
Although x-ray machines remain an essential form of medical imaging, x-rays are a high-energy form of ionizing radiation and high doses are associated with an increased risk of cancer. Keeping x-ray exposure within safe limits limits medical use.
Intense research is underway to identify materials that could increase the sensitivity of X-ray detectors, allowing high-quality medical images to be obtained using very low X-ray doses.
« In recent years, many single-crystal perovskite materials have demonstrated excellent performance in X-ray detection “, explains Xin Song, researcher at KAUST and member of Omar Mohammed’s research group, who led the work.
When an X-ray photon strikes a perovskite semiconductor crystal, it generates a pair of electrical charges, one positive and the other negative. When these charges reach the electrodes at the edges of the perovskite, they create a photocurrent from which X-ray images can be generated.
To further improve the performance of perovskite X-ray detectors, the team targeted the materials’ “dark current.” “. Dark current is mainly caused by heat-generated charge carriers and leakage currents inside the device, she adds.
Dark current in an x-ray detector can obscure low-dose x-ray signals and introduce additional noise. “ This reduces the signal-to-noise ratio and negatively impacts the overall performance of the device », further indicates Ms. Song.
The research team has now demonstrated that an approach called cascade engineering can effectively suppress dark current. “ Cascade engineering involves connecting one type of single crystals in series », says Mr. Mohammed. Connecting crystals in series increases the electrical resistance across the devices. “ This can effectively reduce the dark current and noise of the device without affecting the charge carriers generated by X-rays, thereby improving the performance of the detector and reducing its detection limit.»
The team developed a device based on a perovskite called methylammonium lead bromide (MAPbBr3) to test the concept of cascade engineering. “ This material exhibits relatively high stability and the synthesis process allows the preparation of MAPbBr3 single crystals with excellent reproducibility “, explains Mr. Song. These attributes make this material an ideal candidate for the manufacture of X-ray detectors, with significant commercial potential, she adds.
The researchers tested connections of 1 to 4 single crystals in series and showed that increasing the number of connections in series effectively reduced the dark current. However, increasing the number of crystals also weakened the detection sensitivity of the device. “ We found that connecting two crystals in series achieved the lowest detection limit while maintaining higher sensitivity », specifies Mr. Song. The coupling of two crystals in cascade made it possible to lower the detection limit from 590 nGy-s-1 to only 100 nGy-s-1.
« We are currently investigating the cascade structure for other perovskite single crystals, with the aim of further reducing their detection limits », concludes Mr. Mohammed.
The team is also working on cascading MAPbBr3 single crystals for real-world medical imaging.
Illustration caption: By applying the cascade engineering approach to methylammonium lead perovskite bromide (MAPbBr3), KAUST researchers have developed an X-ray detector with increased performance and a lower detection limit low.
Song, X., Zhang, X., He, T., Wang, J., Zhu, H., Zhou, R., Ahmad, T., Bakr, O.M.& Mohammed, O.F. Revolutionizing X‐ray imaging: A leap toward ultra-low-dose detection with a cascade-engineered approach. ACS Central Science102082–2089 (2024).| Article
Source : Folder
