Stacked Scintillators Based Multispectral X‐Ray Imaging Featuring Quantum‐Cutting Perovskite Scintillators With 570 nm Absorption‐Emission Shift

Traditional energy-integration X-ray imaging systems rely on total X-ray intensity for image contrast, ignoring energy-specific information. Recently developed multilayer stacked scintillators have enabled multispectral, large-area flat-panel X-ray imaging (FPXI), enhancing material discrimination capabilities. However, increased layering can lead to mutual excitation, which may affect the accurate discrimination of X-ray energy. This issue is tackled by proposing a novel design strategy utilizing rare earth ions doped quantum-cutting scintillators as the top layer. These scintillators create new luminescence centers via energy transfer, resulting in a significantly larger absorption-emission shift, as well as the potential to double the photoluminescence quantum yield (PLQY) and enhance light output. To verify this concept, a three-layer stacked scintillator detector is developed using ytterbium ions (Yb³⁺)-doped CsPbCl₃ perovskite nanocrystals (PeNCs) as the top layer, which offers a high PLQY of over 100% and a significant absorption-emission shift of 570 nm. This configuration, CsAgCl₂ and Cs₃Cu₂I₅ as the middle and bottom layers, respectively, ensures non-overlapping optical absorption and radioluminescence (RL) emission spectra. By calculating the optimal thickness for each layer to absorb specific X-ray energies, the detector demonstrates distinct absorption differences across various energy bands, enhancing the identification of materials with similar densities.