Perovskite single crystals with tin–lead gradient for improved ionization radiation detection

Compared with the pure lead-based MAPbBr 3 (MA = CH 3 NH 3 ) perovskite single crystals (PSCs), tin–lead alloy (MAPb x Sn 1−x Br 3 ) PSCs with higher carrier mobility and longer carrier lifetime are expected to perform as better-quality ionization radiation detectors. In this work, we design MAPbBr 3 –MAPb 0.9 Sn 0.1 Br 3 –MAPb 0.8 Sn 0.2 Br 3 structure detectors by employing solution-process epitaxial growth. Because of the gradient change in tin element proportion, the relatively low mismatch rates between different PSC layers can effectively reduce defects generated at the interface, which improves charge collection efficiency. Moreover, band barriers between different PSC layers form depletion layers due to the differences in band structure, and the high resistivity and built-in electric field of depletion layers can suppress dark current under high voltages. The optimized detector exhibits a high x-ray detection sensitivity of 6.76 × 10 4 μ C Gy −1  cm −2 and the lowest detectable dose rate of 7.4 nGy s −1 under 40 kVp x-ray radiation. Based on 241 Am (5.95 MeV) α particle irradiation, tin–lead HD has lower detection noise and more obvious response compared to MAPbBr 3 PSCs. The electron mobility was indicated as high as 612 cm 2  s −1  V −1 , and the mobility-lifetime ( μ τ) products were measured to be 3.5 × 10 −3  cm 2  V −1 using the Hecht equation, demonstrating superior transport properties.