Effect of Dual-Organic Cations on the Structure and Properties of 2D Hybrid Perovskites as Scintillators

Abstract

Two-dimensional (2D) hybrid organic−inorganic perovskite (HOIP) crystals show promise as scintillating materials for wide-energy radiation detection, outperforming their threedimensional counterparts. In this study, we synthesized single crystals of (PEA 2−x BZA x )PbBr 4 (x ranging from 0.1 to 2), utilizing phenethylammonium (C 6 H 5 CH 2 CH 2 NH 3 + ) and benzylammonium (C 6 H 5 CH 2 NH 3 + ) cations. These materials exhibit favorable optical and scintillation properties, rendering them suitable for high light yield (LY) and fast-response scintillators. Our investigation, employing various techniques such as X-ray diffraction (XRD), photoluminescence (PL), time-resolved (TR) PL, Raman spectroscopy, radioluminescence (RL), thermoluminescence (TL), and scintillation measurements, unveiled lattice strain induced by dual-organic cations in powder X-ray diffraction. Density functional theory analysis demonstrated a maximal 0.13 eV increase in the band gap with the addition of BZA cation addition. Notably, the largest Stokes shift of 0.06 eV was observed in (BZA) 2 PbBr 4 . The dual-organic cation crystals displayed >80% fast component scintillation decay time, which is advantageous for the scintillating process. Furthermore, we observed a dual-organic cations-induced enhancement of electron−hole transfer efficiency by up to 60%, with a contribution of >70% to the fast component of scintillation decay. The crystal with the lowest BZA concentration, (PEA 1.9 BZA 0.1 )PbBr 4 , demonstrated the highest LYs of 14.9 ± 1.5 ph/keV at room temperature. Despite a 55−70% decrease in LY for BZA concentrations >5%, simultaneous reductions in scintillation decay time (12−32%) may work for time-offlight positron emission tomography and photon-counting computed tomography. Our work underscores the crucial role of dualorganic cations in advancing our understanding of 2D-HOIP crystals for materials science and radiation detection applications.