X-Site Substituted 2D Cs₂ Pb(SCN)₂ Br₂ Perovskites for X-Ray Detection

2D Ruddlesden-Popper (RP) perovskites have been intensively investigated due to their superior stability and outstanding optoelectrical properties. However, investigations on 2D RP perovskites are mainly focused on A-site substituted perovskites and few reports are on X-site substituted perovskites especially in X-ray detection field. Here, X-site substituted 2D RP perovskite Cs₂ Pb(SCN)₂ Br₂ polycrystalline wafers are prepared and systematically studied for X-ray detection. The obtained wafers show a large resistivity of 2.0 × 10¹⁰ Ω cm, a high ion activation energy of 0.75 eV, a small current drift of 2.39 × 10^-6 nA cm^-1 s^-1 V^-1 , and charge carrier mobility-lifetime product under X-ray as high as 1.29 × 10^-4 cm² V^-1 . These merits enable Cs₂ Pb(SCN)₂ Br₂ wafer detectors with a sensitivity of 216.3 µC Gy_air ^-1 cm^-2 , a limit of detection of 42.4 nGy_air s^-1 , and good imaging ability with high spatial resolution of 1.08 lp mm^-1 . In addition, Cs₂ Pb(SCN)₂ Br₂ wafer detectors demonstrate excellent operational stability under high working field up to 2100 V cm^-1 after continuous X-ray irradiation with a total dose of 45.2 Gy_air . The promising features such as short octahedral spacing and weak ion migration will open up a new perspective and opportunity for SCN-based 2D perovskites in X-ray detection.