Abstract
There are various drawbacks to many scintillators which are currently in widespread use. Conventional inorganic scintillators have fixed emission wavelengths and require expensive, high-temperature synthesis; plastic scintillators, while fast, cheap and robust, have low atomic numbers, limiting their X-ray attenuation. Lead halide perovskite nanocrystals show promise as scintillators due to their high atomic number, bright luminescence and tunable emission wavelength. The aim of this study was to produce a nanocomposite scintillator which incorporates formamidinium lead halide perovskite nanocrystals into a polymer matrix, and to evaluate the viability of this nanocomposite scintillator for gamma-spectroscopy and X-ray imaging applications.
Mixed-halide FAPbBr3xCl3(1−x) nanocrystals were synthesised using a room-temperature solution growth method. Those nanocrystals which contained greater quantities of chlorine had violet emission and short photoluminescence lifetimes, but also had poor stability and weak luminescence intensities. Consequently, FAPbBr3 nanocrystals were selected for use in the nanocomposite scintillators. The thickness and nanocrystal loading of the composites were investigated so as to balance the transparency of the scintillator to visible light with the attenuation of high-energy photons. To reduce optical scattering, the size of the nanocrystals was minimised and a partial
ligand exchange procedure was used to prevent nanocrystal aggregation. However, this surface modification significantly decreased the luminescence intensity of the nanocrystals. Reabsorption also had a significant negative effect on the light output of the nanocomposite scintillators, due to the small Stokes shift of the perovskite nanocrystals. EJ-290 plastic scintillator and PMMA were compared as matrix materials; scintillators which used PMMA had greater radioluminescence intensity, while those which used an EJ-290 matrix had faster decay times.
Overall, despite poor transmission, the optimised formamidinium lead bromide nanocomposite scintillators had a greater detectable light output than the plastic scintillator alone. They also had a faster response time than many common scintillators, and demonstrated great potential for cost-effective X-ray imaging.