X-Site Substituted 2D Cs₂Pb(SCN)₂Br₂ 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 Cs2Pb(SCN)(2)Br-2 polycrystalline wafers are prepared and systematically studied for X-ray detection. The obtained wafers show a large resistivity of 2.0 x 10(10) Omega cm, a high ion activation energy of 0.75 eV, a small current drift of 2.39 x 10(-6) nA cm(-1) s(-1) V-1, and charge carrier mobility-lifetime product under X-ray as high as 1.29 x 10(-4) cm(2) V-1. These merits enable Cs2Pb(SCN)(2)Br-2 wafer detectors with a sensitivity of 216.3 mu C 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, Cs2Pb(SCN)(2)Br-2 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.