Interlayer-Spacing Engineering of Lead-Free Perovskite Single Crystal for High-Performance X-ray Imaging.

Lead-free A 3 Bi 2 I 9 -type perovskites have been demonstrated as a class of promising semiconductors for high-performance X-ray detection due to their high bulk resistivity and strong X-ray absorption, as well as reduced ion migration. However, due to their long interlamellar distance along their c-axis, their limited carrier transport along the vertical direction is a bottleneck for their detection sensitivity. Herein, we design a new A-site cation of aminoguanidinium (AG) with all-NH 2 terminals to shorten the interlayer spacing by forming more and stronger N-H···I hydrogen bonds. The prepared large AG 3 Bi 2 I 9 single crystals (SCs) render shorter interlamellar distance for a larger mobility-lifetime product of 7.94 × 10 -3 cm 2 V -1 , which is 3 times higher than the value measured on the best MA 3 Bi 2 I 9 SC (2.87 × 10 -3 cm 2 V -1 ). Therefore, the X-ray detectors fabricated on the AG 3 Bi 2 I 9 SC exhibit high sensitivity of 5791 uC Gy -1 cm -2 , low detection limit of 2.6 nGy s -1 and short response time of 690 μs, all of which are far better than those of the state-of-the-art MA 3 Bi 2 I 9 SC detectors. The combination of high sensitivity and high stability enables astonishingly high spatial resolution (8.7 lp mm -1 ) X-ray imaging. This work will facilitate the development of low-cost and high-performance lead-free X-ray detectors. This article is protected by copyright. All rights reserved.