Novel Perovskite X-ray/Gamma Detectors and Potential Applications
X-ray imaging has been the mainstay of non-invasive diagnostics in fields such as medicine, security and defence, non-destructive testing and production line quality control. The development of new detectors that offer greater sensitive, energy resolution, radiation hardness and mechanical robustness continues to be a priority to further develop or create new imaging techniques. High energy X-ray and gamma ray detection is particularly important in nuclear security to permit the interception of illegally transported nuclear and radiological materials at the borders, as well as mapping the spread of these materials after a radiological event (accidental or otherwise). The materials used in the construction of new high energy photon detectors must be chosen carefully to ensure efficiency, cost effectiveness and sensitivity, particularly where they must be produced consistently and in volume as in the case for nuclear security applications.
Current research into Perovskite semiconductor materials for solar cell technology has been driven by their excellent light conversion properties; ease and reliability of manufacture; and their relatively low cost. These properties have given rise to significant interest in their potential alternative uses, one of which is in direct X-ray detection 1, owing primarily to their high-Z elemental composition. In this study we present the initial results of two perovskite-based devices exposed to X-rays. Perovskite CsPbBr3 has been synthesised through hydraulic compression or through thermal evaporation and annealing based crystal formation as in 2. The samples formed were either granular powders or single crystals, of 1mm thickness and 5mm thickness respectively, with layers of silver contacts laid down for charge collection. The samples were connected to a voltage source (to provide bias) and a picoameter (to measure photogenerated current). The samples were then exposed to X-ray from a conventional X-ray generator. The current was measured for a range of different bias voltages and X-ray tube potentials. Figure 1 shows the acquired response of the crushed powder Perovskite sample. The dark current was measured to be 0.85 nA (at VBias = 5V) and a response ratio (Ion/Ioff) of up to 86.2 was achieved. The single crystal device demonstrated a higher dark current of 845 nA (at VBias = -5V) and achieved a maximum response ratio of 1.23. The results from both devices are promising, as this production method is cost effective, repeatable and scalable. Further applications of such materials for nuclear security could be in solid state neutron detection by incorporation of Boron-10 in the Perovskite structure.