X-Site Substituted 2D Cs 2 Pb(SCN) 2 Br 2 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 Cs 2 Pb(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 × 10 10 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 cm 2 V -1 . These merits enable Cs 2 Pb(SCN) 2 Br 2 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, Cs 2 Pb(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.