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

Two-dimensional (2D)
hybrid organic–inorganic perovskite
(HOIP) crystals show promise as scintillating materials for wide-energy
radiation detection, outperforming their three-dimensional counterparts.
In this study, we synthesized single crystals of (PEA2–xBZAx)PbBr4 (x ranging from 0.1 to 2), utilizing phenethylammonium
(C6H5CH2CH2NH3+) and benzylammonium (C6H5CH2NH3+) 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)2PbBr4. 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,
(PEA1.9BZA0.1)PbBr4, 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-of-flight positron emission tomography and photon-counting computed
tomography. Our work underscores the crucial role of dual-organic
cations in advancing our understanding of 2D-HOIP crystals for materials
science and radiation detection applications.