Shanghai Silicate has made progress in the research of metal halide scintillation crystal materials

As the key core material of radiation detectors, scintillation crystals have been widely used in high-end medical imaging, homeland security, high-energy physics and other fields
.
In order to meet the sensitivity and confidence requirements of high-performance energy spectrum and imaging detectors, the development of a new type of scintillation crystal material with high light output and high energy resolution has become one of the frontier research directions in the field of radiation detection
.
In recent years, low-dimensional perovskite-structured metal halide materials have the characteristics of confined exciton luminescence, large Stokes shift and high fluorescence quantum efficiency, and have the advantages of no self-absorption and high luminous efficiency, and are considered to be Potential high-performance scintillating material
.
Recently, the team of Wu Yuntao (the research group of halide scintillation crystals), a researcher at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, proposed and designed a series of low-dimensional calcium titanium with strong self-trapped exciton luminescence based on the academic idea of ​​functional element order Mineral metal halide scintillation materials are prepared by the Bridgman descent method and selected several new metal halide scintillation single crystals that are not deliquescent, low melting point, high ray blocking ability, high light output, high energy resolution, and low afterglow.
Through experiments and theoretical calculations, the mechanism of its limited exciton scintillation luminescence is revealed
.
The one-dimensional perovskite structure CsCu2I3 crystal developed by the team has the advantages of high density (5.
01g/cm3), high effective atomic number (Zeff=50.
6), low melting point (371°C), non-deliquescent and no self-absorption
.
The luminescence source is the self-trapped exciton state localized in the [Cu2I6]4-polyhedron, and the luminescence peak is at 570 nm
.
CsCu2I3 crystal has extremely low X-ray excitation afterglow (only 0.
008% at 10 milliseconds), which is four orders of magnitude lower than commercial CsI:Tl crystals
.
Related research results are entitled Non-hygroscopic, self-absorption free, efficient 1D CsCu2I3?perovskite single crystal for radiation detection, published on ACS Appl.
Mater.
Interfaces 13 (2021) 12198-12202..
The zero-dimensional perovskite structure Cs3Cu2I5 crystal developed by the team also has the advantages of high density (4.
52g/cm3), high effective atomic number (Zeff=52.
2), low melting point (383°C), non-deliquescent and no self-absorption
.
Compared with the one-dimensional structure material, the confinement exciton emission of the zero-dimensional structure material has a higher fluorescence quantum efficiency (up to 69.
9%)
.
The light output under X-ray and gamma-ray excitation can reach 30,000 ph.
/MeV, and the energy resolution (@662keV) is better than 3.
4%
.
Related research results are titled Zero-dimensional Cs3Cu2I5?perovskite single crystal as sensitive X-ray and g-ray scintillator, published in Phys.
Status Solidi RRL 14 (2020) 2000374 1-4
.
The team carried out an ion doping optimization study for the Cs3Cu2I5 crystal
.
The study found that Tl+ ion doping can further increase the fluorescence quantum efficiency of Cs3Cu2I5 crystal from 69.
9% to 79.
2%
.
The light output of this crystal material can reach 150,000 ph.
/MeV under X-ray excitation, which is the highest value among known scintillators, and has a very low X-ray detection limit (66.
3nGyair/s), which is only required for medical X-ray diagnosis 1/83
.
In addition, the Cs3Cu2I5:Tl crystal also has excellent gamma-ray detection capabilities, its light output can reach 87,000 ph.
/MeV, and the energy resolution at 662keV is 3.
4%
.
Through theoretical calculations and experimental studies, it is found that the main reason why Tl doping improves the scintillation performance of Cs3Cu2I5 crystals is: the red shift of the emission spectrum after Tl doping reduces the overlap of the excitation emission spectrum, thereby reducing the exciton resonance energy transfer and the quenching of defects.
The formation of Tl0 or Tl2+ Coulomb field attracts electrons and holes to increase the probability of formation of self-trapped exciton states; the formed Tl+ bound exciton states can provide additional radiation transition centers, thereby further improving luminous efficiency
.
The related research results are entitled Ultra-bright and highly efficient all-inorganic zero-dimensional perovskite scintillators, published in Advanced Optical Materials (2021) (DOI: 10.
1002/adom.
2021004), and applied for a national invention patent in China
.
The research work has been funded and supported by the National Natural Science Foundation of China, the Original Exploration Project of the Shanghai Natural Science Foundation, the High-tech Field Project of the Shanghai Science and Technology Commission, and the Zhangjiang Major Special Project
.
The first author of this series of results is the master's research jointly cultivated by Shanghai Institute of Ceramics and University of Shanghai for Science and Technology, Sheng Shuangliang, and Wu Yuntao is the corresponding author of the paper
.
(a) CsCu2I3 single crystal sample, (b) one-dimensional crystal structure of CsCu2I3, (c) variable temperature fluorescence spectrum of CsCu2I3, (d) fluorescence emission spectrum intensity and decay time of CsCu2I3 (a) Cs3Cu2I5:Tl single crystal sample, ( b) Cs3Cu2I5: Tl fluorescence spectrum, (c) zero-dimensional crystal structure of Cs3Cu2I5, (d) Cs3Cu2I5 and Cs3Cu2I5: comparison of light output between Cs3Cu2I5 and Cs3Cu2I5: Tl scintillation crystals and other commercial scintillation crystals