Abstract
X-ray detectors are broadly utilized in medical imaging and product inspection. Halide perovskites recently demonstrate excellent performance for direct X-ray detection. However, ionic migration causes large noise and baseline drift, limiting the detection and imaging performance. Here we largely eliminate the ionic migration in cesium silver bismuth bromide (Cs2AgBiBr6) polycrystalline wafers by introducing bismuth oxybromide (BiOBr) as heteroepitaxial passivation layers. Good lattice match between BiOBr and Cs2AgBiBr6 enables complete defect passivation and suppressed ionic migration. The detector hence achieves outstanding balanced performance with a signal drifting one order of magnitude lower than all previous studies, low noise (1/f noise free), a high sensitivity of 250 µC Gy air−1 cm–2, and a spatial resolution of 4.9 lp mm−1. The wafer area could be easily scaled up by the isostatic-pressing method, together with the heteroepitaxial passivation, strengthens the competitiveness of Cs2AgBiBr6-based X-ray detectors as next-generation X-ray imaging flat panels.
Highlights
X-ray detectors are broadly utilized in medical imaging and product inspection
Huang and co-workers pioneered the use of MAPbBr3 single crystals for X-ray detection and achieved an impressive sensitivity of 21000 μC Gyair−1 cm−2 toward 8 keV X-rays[3,4]
Cs2AgBiBr6 single crystal-based detector achieved a moderate sensitivity of 105 μC Gyair−1 cm–2 and a low detection limit of 59.7 nGyair s−1, which is comparable to the best-performing lead halide perovskite X-ray detectors[5]
Summary
X-ray detectors are broadly utilized in medical imaging and product inspection. Halide perovskites recently demonstrate excellent performance for direct X-ray detection. Metal halide perovskites have demonstrated excellent X-ray detection performance, due to the high X-ray attenuation coefficient, defect tolerance nature, and large mobility-lifetime product (μτ)[2,3,4,5]. Cs2AgBiBr6 as a promising non-toxic alternative with similar key features as lead halide perovskites, including a large μτ product of about 10–3 cm[2] V−1, high X-ray absorption coefficient and larger resistivity (109 to 1011 Ω cm)[7]. Cs2AgBiBr6 single crystal-based detector achieved a moderate sensitivity of 105 μC Gyair−1 cm–2 and a low detection limit of 59.7 nGyair s−1, which is comparable to the best-performing lead halide perovskite X-ray detectors[5]. Area scalability and ionic migrations are current two bottlenecks of perovskite X-ray detectors for their further employment in X-ray imaging. Polycrystalline films capable of area-scalable fabrication are a feasible route toward such applications
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