(BZA)2PbBr4: Ultrafast Scintillation Detector with Potential for Photon-Counting CT

Photon-counting computed tomography (PCCT) is a rapidly emerging medical imaging technology. Several PCCT scanners have been developed in recent years, using finely pixelated room-temperature semiconductor detectors (RTSD) such as CdTe, Cd
(1-x)
Zn
x
Te (CZT), and Si. Whereas scintillation detectors were traditionally considered too slow to handle the X-ray fluence rates > 10
⁸
photons s
^-1
mm
^-2
encountered in clinical PCCT, we have recently demonstrated how the properties of modern scintillators and silicon photomultipliers (SiPMs) force us to rethink this paradigm. It appears that indirect detection using ultrafast scintillators and SiPMs may provide a robust, scalable, and cost-effective X-ray photon-counting technology. Here, we evaluate a new, solution-processable, two-dimensional (2D) perovskite scintillator, benzylamonium lead bromide or (BZA)
2
PbBr
4
, as a candidate material for PCCT. Experimental characterization of this material reveals an approximately 4 ns decay time constant under X-ray excitation at 300 K, combined with a light yield of 3.7 photons/keV and an energy resolution of 8% FWHM at 662 keV. The emission spectrum with its maximum at 432 nm matches well with the photodetection efficiency (PDE) curve of typical SiPMs. Pulses produced by a SiPM-based (BZA)
2
PbBr
4
detector were modeled using the simulation tool previously developed by Van der Sar et al. The ultrafast decay of (BZA)
2
PbBr
4
results in outstanding count-rate capability per detector pixel, outperforming that of CZT detectors described in literature. Combined with its cost-effective, solution-based synthesis, this makes (BZA)
2
PbBr
4
a promising indirect-conversion material for PCCT.