Large Scale Lead-Free Perovskite Polycrystalline Wafer Achieved by Hot-Pressed Strategy for High-Performance X-Ray Detection.

Halide perovskites (HPs) have demonstrated excellent direct X-ray detection performance. Lead-free perovskite polycrystalline wafers have outstanding advantages in large-area X-ray imaging applications due to their area-scalability, thickness-controllability, large bulk resistivity, and ease of integration with large-area thin film transistor arrays. However, currently lead-free perovskite polycrystalline wafers possess low sensitivity, typically less than 1000 µC Gy ^-1 cm ^-2 , which severely limits their X-ray detection applications. Here, high-quality and large scale polycrystalline wafers of AG ₃ Bi ₂ I ₉ (AG: aminoguanidinium) with short intercluster distances are successfully prepared using a hot-pressing method. The wafers possess high mobility-lifetime product of 5.66 × 10 ^-3 cm ² V ^-1 and therefore achieve high X-ray sensitivity of 2675 µC Gy ^-1 cm ^-2 , which can be comparable to those of the high-quality single crystal counterpart reported by the previous research (7.94 × 10 ^-3 cm ² V ^-1 and 5791 µC Gy ^-1 cm ^-2 ), and represent the best results of the currently lead-free HP polycrystalline wafers. Besides, the wafers exhibit the X-ray detection limit as low as 11.8 nGy s ^-1 , excellent long-term working stability, and high spatial resolution of 5.9 lp mm ^-1 in imaging. The findings demonstrate that AG ₃ Bi ₂ I ₉ polycrystalline wafers are feasible for high-performance X-ray detection and imaging system.
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