Photophysics in Zero‐Dimensional Potassium‐Doped Cesium Copper Chloride Cs₃Cu₂Cl₅ Nanosheets and Its Application for High‐Performance Flexible X‐Ray Detection

Abstract

X-ray detectors with high performance, durability, and flexibility detectors are required for a wide range of applications in several fields, such as medical treatment (imaging, diagnostic radiology, etc.), nondestructive testing (radioscopic inspections, radiography testing, etc.), security and defense (luggage/body scanning systems, paper mail, etc.), nuclear and radiation industries (nuclear power plants, research reactors, users of nuclear gauges, etc.), and scientific research and development. [1]-[9] Thereof, indirect X-ray detectors are widely used for ordinary flat panel X-ray detection, among which scintillator is the most important factor affecting the detection performance. [10][11][12][13][14] Currently, the ideal scintillator should meet the following basic conditions: (i) good stopping power and excellent radiation absorption, [15]-[18] (ii) high photoluminescence (PL) with large Stokes shift and radioluminescence (RL) intensity, (iii) nontoxicity with environmentally stable, [19] (iv) easily manufactured and extendable to large-area flexible applications. [20,21] Among all, inorganic copper (I)-based metal halide semiconductors meeting all the above requirements are considered as promising candidates. In particular, zero-dimensional (0D) cesium copper chloride, Cs 3 Cu 2 Cl 5 , shows excellent photoelectric performance in ultraviolet photodetectors. [22] With isolated [Cu 2 Cl 5 ] 3dimers and Cs + ions, Cs 3 Cu 2 Cl 5 is expected to exhibit intriguing optical properties mainly derived from self-trapped excitons (STEs). Different from the narrow and rapid emission of free excitons and inter-band recombination, the emission of STEs is featured with broad spectra and large Stokes shifts. Generally, the STEs emission that occurs in Cs 3 Cu 2 Cl 5 originates from structural deformation of [Cu 2 Cl 5 ] 3− dimers. [23] At the time of photoexcitation, the Cu-Cl bonds elongate (shrink) on the equatorial plane but shrink (elongate) in the axial direction, which in turn causes the local structure change from a high symmetry to a low symmetry configuration.To further improve its photophysical characteristics, the diversified structural optimization in Cs 3 Cu 2 Cl 5 could offer deeper insights and more controlling knobs on STEs emission. Zero-dimensionalCs 3 Cu 2 Cl 5 exhibits intriguing optical properties, which can meet the basic requirements of ideal scintillator application. Here, green emitter Cs 3 Cu 2 Cl 5 nanosheets are successfully synthesized, and by doping with 2% potassium (K + ), their photoluminescence quantum yield (70.23% to 81.39%), radioluminescence intensity, and stability are improved. Further experimental and theoretical studies point out that: (1) K + brings the neighboring [Cu 2 Cl 5 ] 3− dimers groups closer, leading to lattice shrinkage and lower lattice constants; (2) such compact crystal structure results in stronger exciton-photon coupling and reduced phonon-electron coupling strength, which is beneficial to form self-trapped excitons and enhanced luminescence; (3) lower lattice ...

Metal‐Free PAZE‐NH4X3⋅H2O Perovskite for Flexible Transparent X‐ray Detection and Imaging

“…According to the gradient photocurrent difference of each pixel, the rigid devices present more or less distortion for the nonuniform spatial distribution of X-ray dose, which is highlighted in Figure 5c. [58] Differently, the flexible device could be comfortably attached to the curving object, and realize better imaging figures. Notably, the contrast between flexible and rigid images is not clear enough, which may be ascribed to the appearance of the signal/electrical crosstalk in the 3 × 3 pixelated X-ray imager.…”

Aggregation-Induced Fluorescence Enhancement for Efficient X-ray Imaging Scintillators and High-Speed Optical Wireless Communication

“…More importantly, due to the transparent characteristics of the AIEgen screens, a high X-ray imaging resolution of 16.3 lp mm –1 was obtained for the TPE-Br film, which exceeded the resolutions of most organic and inorganic scintillation materials that have been reported (Figure e and Table S2). ,− , This high spatial resolution was further confirmed by the line-pair card image, in which a line of 16.6 lp mm –1 can be recognized (Figure f). We then performed a series of imaging tests using TPE-Br scintillators to further demonstrate their potential in high-resolution X-ray imaging applications.…”

“…In addition, the high PLQY and short lifetimes of these AIEgens in the aggregated state, which were well confirmed by steady-state and ultrafast time-resolved mid-infrared (mid-IR) spectroscopy and DFT calculations, greatly increased their -3-dB modulation bandwidth and net data rate in OWC applications. The AIEgen-based scintillators exhibit a high X-ray imaging resolution of 16.3 lp mm –1 , which is comparable with those of many conventional organic and inorganic scintillation materials, ,− making them excellent candidates for X-ray radiography. In addition, these AIEgens show a broad -3-dB modulation bandwidth of ∼110 MHz and high net data rates of ∼600 Mb/s; these are much higher than those of most conventional materials, demonstrating the high potential of AIEgens for use in high-speed OWCs.…”

High-Resolution X-ray Imaging Based on Solution-Phase-Synthesized Cs3Cu2I5 Scintillator Nanowire Array

“…Recently, the lead-free Cu­(I)-based metal halides, represented by Cs 3 Cu 2 I 5 , are favored as scintillators due to their solution-processability, high photoluminescence quantum yield (PLQY), large Stokes shift, and negligible self-absorption. − Many studies focus on the synthesis of Cs 3 Cu 2 I 5 scintillators, including nanocrystals (NCs), ,, single crystals (SCs), , and polycrystalline powder, and their applications in X-ray detection and imaging. However, the imaging resolution is still rather limited due to the lack of a scintillation waveguide, especially for the solution-processed nanocrystal scintillators. ,,,, The spatial resolution is one of the key indicators to evaluate scintillation performance, which largely depends on the geometry and morphology of the scintillation screen (i.e., thickness, dimension, and shape). − …”