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

Abstract 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 (Yb 3+ )‐doped CsPbCl 3 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, CsAgCl 2 and Cs 3 Cu 2 I 5 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.