3D/2D Core-Shell CsPbBr₃ Microcrystals for Stable X-Ray Detection and Imaging

Although metal halide perovskite (MHP) materials are promising candidates for direct X-ray detection, the surface and internal defects of perovskite polycrystalline thick films lead to severe noise current and poor device stability. Herein, a phenylethylammonium (PEA+) cladding layer was integrated with 3D CsPbBr3 grains, forming 3D/2D core-shell CsPbBr3 perovskite microcrystals. The PEA+, acting as the A-site cation, is able to passivate the surface defects, while the forming 2D perovskite cladding layer inhibits ion migration within CsPbBr3 grains. The blade-coated polycrystalline 3D/2D core-shell CsPbBr3 perovskite thick film exhibits a reduced trap density from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${4}.{32}\times {10} ^{{10}}$ </tex-math></inline-formula> cm−3 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${4}.{26}\times {10} ^{{9}}$ </tex-math></inline-formula> cm−3 compared to conventional CsPbBr3 film, with ion migration activation energy increasing from 123 meV to 210 meV. Consequently, the obtained perovskite X-ray detector exhibits a high sensitivity of 29,<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$460~\mu $ </tex-math></inline-formula> C Gy<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${}_{\text {air}}^{-{1}}$ </tex-math></inline-formula> cm−2 and a low detection limit of 84 nGyair s−1 (50 keV X-ray photon energy), and the detector maintains long-term operational stability with a dark current drift as low as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${4}.{12}\times {10} ^{-{5}}$ </tex-math></inline-formula> nA mm−1 s−1 V−1. Furthermore, we integrated the 3D/2D core-shell polycrystalline CsPbBr3 with a TFT chip (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${64}\times {64}$ </tex-math></inline-formula> array) and successfully obtained a clear and high-contrast X-ray image of a mouse’s paw exhibiting a spatial resolution of 2.5 lp mm−1.