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

Abstract 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.