No 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 (Cs 2 AgBiBr 6 ) polycrystalline wafers by introducing bismuth oxybromide (BiOBr) as heteroepitaxial passivation layers. Good lattice match between BiOBr and Cs 2 AgBiBr 6 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 Cs 2 AgBiBr 6 -based X-ray detectors as next-generation X-ray imaging flat panels.

Double perovskite Cs 2 AgInCl 6 is newly reported as a stable and environmentally friendly alternative to lead halide perovskites. However, the fundamental properties of this material remain unexplored. Here, we first produced high-quality Cs 2 AgInCl 6 single crystals (SCs) with a low trap density of 8.6 × 10 8 cm −3 , even lower than the value reported in the best lead halide perovskite SCs. Through systematical optical and electronic characterization, we experimentally verified the existence of the proposed parity-forbidden transition in Cs 2 AgInCl 6 and identified the role of oxygen in controlling its optical properties. Furthermore, sensitive (dectivity of ∼10 12 Jones), fast (3 dB bandwidth of 1035 Hz), and stable UV photodetectors were fabricated based on our Cs 2 AgInCl 6 SCs, showcasing their advantages for optoelectronic applications.