Zero‐Dimensional Cs₃Cu₂I₅ Perovskite Single Crystal as Sensitive X‐Ray and γ‐Ray Scintillator

Abstract

Organic-inorganic hybrid halide perovskites, represented by CH 3 NH 3 PbX 3 (X ¼ Cl, Br, I), have demonstrated excellent optoelectronic and radiation detection properties. [1-3] All-inorganic CsPbX 3 perovskites (X ¼ Cl, Br, I) with better long-term stability are also considered as promising materials for optoelectronic devices and semiconductor γ-ray detectors. [4-6] Recently, there has been a surge of interest in low-dimensional perovskites due to their high photoluminescence quantum yield (PLQY). For example, the crystal structure of Cs 4 PbBr 6 that consist of spatially isolated [PbBr 6 ] 4À octahedra surrounding with Cs þ ions can be regarded as a 0D structure at molecular level, which leads to an intense quantum confinement effect. Excitons are strongly confined at each [PbBr 6 ] 4À octahedron, enabling a high exciton binding energy of 353 meV and a high PLQY of between 42% and 45%. [7,8] Quite a few low-dimensional allinorganic perovskites with remarkable luminescent properties were also reported as sensitive and efficient scintillators. Bulk crystals of 0D Cs 4 CaI 6 :Eu, Cs 4 SrI 6 :Eu, and Cs 4 EuBr 6 perovskites, isostructural to K 4 CdCl 6 trigonal system, have excellent light yields from 51 800 to 78 000 photons MeV À1 and energy resolutions from 3.3% to 4.3% at 662 keV. [9,10] However, due to a small Stokes shift of Eu 2þ ions, these materials suffer from strong self-absorption effect when scaling-up crystal size. Nanocrystals of 0D CsPbBr 3 /Cs 4 PbBr 6 perovskites show a high light yield of 64 000 photons MeV À1 and a fast decay time of <10 ns. [11] Onedimensional materials were also reported as sensitive X-ray scintillators, such as Rb 2 CuBr 3 and Rb 2 CuCl 3. [12,13] In particular, the Rb 2 CuBr 3 , that is self-absorption free and nonhygroscopic, was reported to achieve an ultrahigh scintillation yield of 90 000 photons MeV À1. [12] All-inorganic 0D perovskite Cs 3 Cu 2 I 5 was recently reported as a highly efficient blue-emitting material with a PLQY of 91.2%, and regarded as promising for application in photodetectors, light-emitting diodes, and memristors afterward. [14-17] In 2020, Cs 3 Cu 2 I 5 nanocrystals were developed for X-ray imaging with a light yield of 80 000 photons MeV À1. [18] To the best of our knowledge, the X-ray and γ-ray detection capability of bulk Cs 3 Cu 2 I 5 single crystal has not been reported. Thus, the aim of this work is to study the physical and optical properties and the scintillation performance under X-ray and γ-ray radiation of high-quality Cs 3 Cu 2 I 5 perovskite single crystal grown by the Bridgman method. The 7 mm diameter single crystal of Cs 3 Cu 2 I 5 was grown by the vertical Bridgman method. High-purity powders of CsI (99.99%, Grirem Advanced Materials) and CuI (99.999%, Sigma-Aldrich) were used as raw materials. These starting materials were mixed consistent with stoichiometric ratio and loaded into a quartz ampoule in a glovebox with <0.1 ppm moisture and oxygen. The loaded ampoule was sealed under a vacuum of 10 À6 torr after drying at 180 C for ...

Embedding Cs3Cu2I5 Scintillators into Anodic Aluminum Oxide Matrix for High‐Resolution X‐Ray Imaging

“…In Cs 3 Cu 2 I 5 crystal, photoactive sites of [Cu 2 I 5 ] 3− are isolated by Cs + cations to form 0D crystal structure. [23,26] Consistent with the 0D crystal structure, the obtained Cs 3 Cu 2 I 5 crystals were granular before grinding for the hotpressing as starting materials (Figure 2a inset and Figure S1a,b, Supporting Information). The phase purity of Cs 3 Cu 2 I 5 was confirmed by Rietveld refinement of powder X-ray diffraction (PXRD) patterns with a goodness-of-fit parameter χ 2 of 8.904 and reliability factors R wp = 6.77% and R p = 3.94%, confirming that Cs 3 Cu 2 I 5 belongs to an orthorhombic space group of Pnma (Figure S1c,d, Supporting Information).…”

“…As a result, Cs 3 Cu 2 I 5 is an attractive candidate for excellent pixelated scintillator films. [23] Herein, we propose a strategy to prepare pixelated scintillator films and take Cs 3 Cu 2 I 5 as the prototype to fabricate Cs 3 Cu 2 I 5 -AAO scintillator films through the hot-pressing method. Particularly, the well-defined porous structure and the small refractive index make the AAO template a suitable matrix that facilitates the formation of hexagonally aligned Cs 3 Cu 2 I 5 (n = ≈1.87) columnar crystal surround by an optically thinner medium Al 2 O 3 (n = ≈1.78).…”

Undoped and Tl‐Doped Cs3Cu2I5 Thin Films as Potential X‐ray Scintillators

“…Its decay time is 1088 ns consistent with the value found in the bulk crystal. [ 15 ] Its broad emission ranging from 350 to 550 nm, a large Stokes shift of 1.29 eV, and microsecond decay time are indicative of the STE emission nature. [ 20 ] In Figure 2(d), the undoped Cs 3 Cu 2 I 5 thin film shows a high PLQY of 76.2%.…”

“…Undoped Cs 3 Cu 2 I 5 film has a fast component of 99 ns (11%) and a slow component of 911 ns (89%), close to the results of Cs 3 Cu 2 I 5 single crystals. [ 15,17 ] Tl‐doped Cs 3 Cu 2 I 5 film has a fast component of 98 ns (12%) and a slow component of 885 ns (88%). The decay features of Tl + and STE could not be well separated, but it is clear that the dominant slow decay component of Tl‐doped Cs 3 Cu 2 I 5 film is faster than that of undoped Cs 3 Cu 2 I 5 film due to the contribution from faster Tl + emission.…”

“…[ 14 ] In our previous work, bulk crystals of undoped and Tl‐doped Cs 3 Cu 2 I 5 were successfully grown by the Bridgman method. [ 15,16 ] The undoped Cs 3 Cu 2 I 5 single crystal can achieve a scintillation yield of 32 000 photons MeV −1 and an ultralow afterglow of 0.03% at 10 ms after X‐ray cutoff. By Tl + doping, the scintillation yield of Cs 3 Cu 2 I 5 single crystal was significantly enhanced up to about 90 000 photons MeV −1 under 137 Cs source excitation.…”