The organic-inorganic hybrid lead halide perovskites have emerged as a series of star materials for solar cells, lasers and detectors. However, the issues raised by the toxic lead element and marginal stability due to the volatile organic components have severely limited their potential applications. In this work, we develop a nucleation-controlled solution method to grow large size high-quality Cs3Bi2I9 perovskite single crystals (PSCs). Using the technique, we harvest some centimeter-sized single crystals and achieved high device performance. We find that X-ray detectors based on PSCs exhibit high sensitivity of 1652.3 μC Gyair−1 cm−2 and very low detectable dose rate of 130 nGyair s−1, both desired in medical diagnostics. In addition, its outstanding thermal stability inspires us to develop a high temperature X-ray detector with stable response at up to 100 °C. Furthermore, PSCs exhibit high X-ray imaging capability thanks to its negligible signal drifting and extremely high stability.

By fine-tuning the crystal nucleation and growth process, a low-temperature-gradient crystallization method is developed to fabricate high-quality perovskite CH NH PbBr single crystals with high carrier mobility of 81 ± 5 cm V s (>3 times larger than their thin film counterpart), long carrier lifetime of 899 ± 127 ns (>5 times larger than their thin film counterpart), and ultralow trap state density of 6.2 ± 2.7 × 10 cm (even four orders of magnitude lower than that of single-crystalline silicon wafers). In fact, they are better than perovskite single crystals reported in prior work: their application in photosensors gives superior detectivity as high as 6 × 10 Jones, ≈10-100 times better than commercial sensors made of silicon and InGaAs. Meanwhile, the response speed is as fast as 40 µs, ≈3 orders of magnitude faster than their thin film devices. A large-area (≈1300 mm ) imaging assembly composed of a 729-pixel sensor array is further designed and constructed, showing excellent imaging capability thanks to its superior quality and uniformity. This opens a new possibility to use the high-quality perovskite single-crystal-based devices for more advanced imaging sensors.

Inch-sized (26 3 26 3 8 mm 3 ), 0D-structured, lead-free, halide perovskite (CH 3 NH 3 ) 3 Bi 2 I 9 single crystals are grown for a high-performance X-ray detector. The X-ray detector shows high sensitivity of 1,947 mC Gy air À1 cm À2 , low detection limit of 83 nGy air s À1 , and short response time of 23.3 ms. The combination of large crystal size and excellent X-ray response allows us to design and fabricate the first 0D-structured lead-free perovskite X-ray imaging system with high resolution.

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