Two-Dimensional Perovskite with Long-Chain Organic Cations for High-Performance X-ray Scintillator

2D hybrid organic–inorganic perovskites (HOIPs) have emerged as promising scintillator materials. Organic cations composed of long chains typically lead to larger interlayer distances between inorganic layers, which could potentially enhance the excitonic confinement. However, as the chain length increases, the interlayer interaction force weakens, leading to more significant octahedral distortion. Here, a novel 2D HOIP ((Br-PA)₂PbBr₄) (PA = pentylamine) with a large interlayer distance (9.40 Å) and small octahedral distortion has been synthesized through synergistic regulation of the chain length and interlayer interaction. The organic cation Br-PA connects to the inorganic layer through a hydrogen bond at one end and links to another inorganic layer through a halogen bond at the other end, thus enhancing interlayer interaction and minimizing the structural distortion. The photoluminescence quantum yield (PLQY) of (Br-PA)₂PbBr₄ (16.34%) was significantly higher than that of PA₂PbBr₄ (∼1.41%) and also exceeded that of the previous 2D HOIPs with an alkane chain cation. Moreover, the (Br-PA)₂PbBr₄ scintillator exhibited a high light yield toward X-rays, comparable to that of a commercial LYSO:Ce scintillator, and a high spatial resolution of 27.2 lp mm^–1, exceeding those of nearly all reported scintillators. This work provides crystal structural insights into the rational design of 2D perovskites for new scintillators.