Dion‐Jacobson 2D Perovskite 2AMPPbBr ₄ with Type II Band Alignment for Highly Sensitive X‐Ray Detection

Abstract 2D hybrid perovskites have emerged as a promising alternative material to address the environmental stability and the ion‐migration of the 3D perovskites for direct X‐ray detector applications. Nevertheless, the X‐ray detection performance of the 2D hybrid perovskites still lags because of its low X‐ray attenuation ability and limited solubility for thick film deposition. Here, a high‐performance X‐ray detector in Dion‐Jacobson 2D hybrid perovskite, 2(aminomethyl) pyridinium lead bromide (2AMPPbBr ₄ ), is studied. 2AMPPbBr ₄ exhibits an ultra‐short interlayer distance of 3.43 Å, leading to high X‐ray attenuation ability. Furthermore, DFT results indicate that 2AMPPbBr ₄ exhibits type II band alignment between 2AMP ²⁺ ligand and the [PbI ₆ ] ⁴⁻ layers, facilitating effective spatial separation of photo‐generated carriers. The X‐ray detector made of 2AMPPbBr ₄ with an average thickness of 200 µm is realized via an improved drop‐casting method. An improved X‐ray sensitivity of 3933.88 µC Gy ⁻¹ cm ⁻² and a low detection limit of 4.17 nGy s ⁻¹ is achieved. This work paves the way for high‐performance X‐ray detectors based on the emerging 2D perovskite materials.