  Conventional energy-integration black-white X-ray imaging lacks spectral
information of X-ray photons. Although X-ray spectra (energy) can be
distinguished by photon-counting technique typically with CdZnTe detectors, it
is very challenging to be applied to large-area flat-panel X-ray imaging
(FPXI). Herein, we design multi-layer stacked scintillators of different X-ray
absorption capabilities and scintillation spectrums, in this scenario, the
X-ray energy can be discriminated by detecting the emission spectra of each
scintillator, therefore the multispectral X-ray imaging can be easily obtained
by color or multispectral visible-light camera in one single shot of X-ray. To
verify this idea, stacked multilayer scintillators based on several emerging
metal halides were fabricated in the cost-effective and scalable solution
process, and proof-of-concept multi-energy FPXI were experimentally
demonstrated. The dual-energy X-ray image of a bone-muscle model clearly showed
the details that were invisible in conventional energy-integration FPXI. By
stacking four layers of specifically designed multilayer scintillators with
appropriate thicknesses, a prototype FPXI with four energy channels was
realized, proving its extendibility to multispectral or even hyperspectral
X-ray imaging. This study provides a facile and effective strategy to realize
energy-resolved flat-panel X-ray imaging.
