Highly Stable Zero-Dimensional Lead-Free Metal Halides for X-ray Imaging

Abstract

Scintillators are widely used for radiation detection in various fields, such as medical imaging, nondestructive testing, and crystallography. X-ray-generating systems typically emit large amounts of heat and require a high thermal stability of scintillators, particularly for nondestructive testing or radiation detection performed under harsh conditions. Therefore, highly stable scintillators must be developed for application in extreme environments. Herein, we developed new zero-dimensional lead-free monoclinic phases of Cs 3 TbCl 6 and Rb 3 TbCl 6 metal halides that are thermally and chemically stable. Cs 3 TbCl 6 and Rb 3 TbCl 6 polycrystals exhibit high light yields of 56800 and 88800 photons/MeV, respectively. Cs 3 TbCl 6 and Rb 3 TbCl 6 polycrystals also show low detection limits of 149.65 and 115.38 nGyairs −1 due to their structural−optical properties, respectively. Furthermore, the fabricated thick films of Cs 3 TbCl 6 and Rb 3 TbCl 6 are applied to our homemade X-ray imaging system, and preferable spatial resolutions are obtained as compared with a commercial Gd 2 O 2 S:Tb 3+ film.S cintillators that convert high-energy photons (such as Xrays) to low-energy visible photons have become crucial for a wide range of applications, including medical diagnostic imaging, nondestructive testing, crystallography, quality inspection, security, etc. Materials such as CsI (CsI:TI), LYSO (Lu,Y) 2 SiO 5 :Ce 3+ ), and GOS (Gd 2 O 2 S:Tb 3+ ) are currently widely used as scintillators in indirect X-ray detectors. 1−4 However, they have several limitations such as complicated synthesis processes and poor thermal stability. 5−7 Recently, lead halide perovskites (LHPs) have attracted significant attention as scintillators due to their low detection limits and the possibility of multicolor radioluminescence (RL). 8−12 However, the main drawbacks of the LHPs as scintillators are low thermal and chemical stability and selfabsorption properties of LHPs. Moreover, the inherent toxicity of lead is a critical limitation of LHPs. 13−16 Recently, lead-free metal halides have been developed as scintillators. 17,18 For instance, Yang et al. reported that Rb 2 CuBr 3 was as a scintillator with a high light yield 19 and Zhang et al. applied Rb 2 AgBr 3 , with its short scintillation decay time, to dynamic Xray imaging. 20 In addition, Jiang et al. applied C 4 H 12 NMnCl 3 and (C 8 H 20 N) 2 MnBr 4 for a WLED and X-ray scintillator. 21 Recently, Tb 3+ -doped metal halides have attracted attention due to their interesting luminescence properties. Liu et al. reported persistent radioluminescence and excellent X-ray imaging using NaLuF 4 :Tb 3+ . 22,23 However, despite these excellent findings, no studies have been able to overcome the

Density-discriminating chromatic x-ray imaging based on metal halide nanocrystal scintillators

“…Inorganic and hybrid metal halide scintillators show a remarkable difference in radiation absorption coefficient and luminescence color due to the wide component tunability, which is facile for choosing the appropriate combination to realize chromatic x-ray imaging (25)(26)(27)(28)(29). Here, 79-μm (BA) 2 PbBr 4 :Mn and 17-μm Cs 3 Cu 2 I 5 :Tl NC scintillator films were chosen as the first and second scintillator layers because (BA) 2 PbBr 4 :Mn can be optimized to achieve efficient long-wavelength RL emission at ~605 nm (fig.…”

High-Throughput Screening on Halide Perovskite Derivatives and Rational Design of Cs3LuCl6

“…Next, for the B-site cation, we considered a lead-free series to find alternatives for toxic lead. Generally, Sn, Sb, Ge, and Bi are known as conventional lead-free elements. , In addition to these, new lead-free series have recently been discovered in transition metals, ,− post-transition metals, ,− and even lanthanides. ,, These series exhibit moderate environmental stability with usable optoelectronic performance but are still extremely uncommon. Hence, 36 lead-free metals encompassing transition metals, post-transition metals, and lanthanides were selected as the B-site cations, excluding certain precious and toxic elements.…”

“…This reduction of connectivity can enhance their environmental stability, improve moisture resistance, and allow for tunable bandgaps, which make them promising candidates for various optoelectronic applications. 10,11 The example cases are Cs-Mn-Cl 12 in A 2 B 1 X 4 , Cs-Tb-Cl 13 and Cs-Sc-Cl 14 in B 3 B 1 B 6 , and so on. Their compositional diversity and structural dimensionality, 15,16 however, require numerous efforts to explore novel materials in almost infinite chemical spaces despite their promising potentials.…”

“…18,19 In addition to these, new lead-free series have recently been discovered in transition metals, 14,23−26 post-transition metals, 8,27−30 and even lanthanides. 13,31,32 These series exhibit moderate environmental Scheme 1. Workflow of Computational Exploration for Inorganic Halide Perovskite Derivatives Figure 1.…”

“…The conventional ABX 3 perovskite structure has 3D connectivity of BX 6 octahedra; however, such a polyhedral connectivity in perovskite derivatives can be reduced to 2D, 1D, or even 0D by choosing a heterovalent B ion (replacing Pb 2+ ) or changing the stoichiometry. This reduction of connectivity can enhance their environmental stability, improve moisture resistance, and allow for tunable bandgaps, which make them promising candidates for various optoelectronic applications. , The example cases are Cs-Mn-Cl in A 2 B 1 X 4 , Cs-Tb-Cl and Cs-Sc-Cl in B 3 B 1 B 6 , and so on. Their compositional diversity and structural dimensionality, , however, require numerous efforts to explore novel materials in almost infinite chemical spaces despite their promising potentials. − Thereby the development in the field of perovskite derivatives is still in its infancy, necessitating further systematic investigations, including the integration of machine learning (ML) and density functional theory (DFT) computations. , In addition, understanding low-dimensional inorganic metal halides’ physical and chemical nature still remains a mystery .…”