Zn (II)‐Doped Cesium Copper Halide Nanocrystals with High Quantum Yield and Colloidal Stability for High‐Resolution X‑Ray Imaging

Abstract

and adjustable bandgap, thereby exhibiting extraordinary X-ray detection performance. [1] To date, high-quality lead-based perovskite single crystals have demonstrated ultrahigh detection performance. However, they are limited by their current shortcomings, including the toxicity of lead, chemical instability, inherent brittleness of bulk crystals, and their hightemperature fabrication and complex processes. [2] Therefore, the development of low-cost, environmentally friendly, flexible X-ray detectors, and novel scintillators still remain a challenge.Owing to the high emission stability, low self-absorption, soft lattice, unique self-trapped exciton emission (STE), [3] and relatively low toxicity and earth-abundant composition, lead-free copper-based halide Cs 3 Cu 2 I 5 nanocrystals (NCs) have attracted extensive attention in the field of optoelectronics, [4] such as electroluminescent lightemitting diode (LED) devices, [5] ultraviolet (UV) photodetectors, [6] X-ray imaging, [7] and anticounterfeiting technology. [8] Although progress has been made in the synthesis and application of Cs 3 Cu 2 I 5 NCs, [9] the insufficient synthesis reaction and difficulty in controlling the crystal size, morphology, and uniformity of Cs 3 Cu 2 I 5 NCs still remain the main obstacles hindering device performance and fundamental research. [10] Metal ion doping is an effective way to tune the structure and optoelectronic properties of materials, which Scintillators are essential for high-energy radiation detection in a variety of potential applications. However, due to complex fabrication processes and nanocrystal homogeneity, conventional scintillators are challenging to meet the need for cost-effective, environmentally friendly, and flexible X-ray detection. Here, monodisperse nanocrystals (NCs) with small grain size and colloidal stability are obtained by adjusting the doping concentration of Zn 2+ ions and controlling the morphology uniformity of Cs 3 Cu 2 I 5 NCs. The photoluminescence quantum yield (PLQY) for the optimal doping concentration is as high as 92.8%, which is a 28.5% improvement compared to nondoped NCs. Density functional theory calculations reveal that the Zn 2+ dopant inclines to occupy Cu sites and the I-rich condition suppresses the formation of I vacancy, enriching the excited electron density at the band-edge to enhance the self-trapped exciton emission. Moreover, high luminescence performance and flexible X-ray scintillator films are prepared using Zn 2+doped Cs 3 Cu 2 I 5 NCs, with a spatial resolution of up to 15.7 lp mm -1 . This work provides an effective strategy for the development of environmentally friendly, low-cost, and efficient blue-emitting 0D all-inorganic metal halides, as well as shows their great potential for high-performance flexible lead-free and low-toxicity X-ray detector applications.

High-Quality Cs3Cu2I5@PMMA Scintillator Films Assisted by Multiprocessing for X-ray Imaging

“…However, there are still some problems to be solved in order to achieve practical commercial applications of copper-based metal halide scintillators. First, the intrinsic poor stability makes metal halide scintillators exposed to the air, making it difficult to achieve long-term applications. , Second, the surface defects can hugely decrease the RL efficiency of scintillator nanocrystals (NCs), which makes it difficult to achieve high-resolution X-ray imaging. , The third issue is that currently most scintillator devices are packaged with a simple mixture of powder scintillators and polymers, which makes it difficult to obtain high-quality and uniform scintillator films. − Based on this, the development of in-situ crystalline scintillator films can effectively solve the instability and packaging problems of copper-based metal halide and can also achieve flexible X-ray imaging. In our former research, it found that the CsPbBr 3 NCs can in-situ grow in precured polymer polymethyl methacrylate (PMMA) with high viscosity like as a “polymer ceramics”, which achieved flexible and high-resolution X-ray imaging .…”

“…29,30 Second, the surface defects can hugely decrease the RL efficiency of scintillator nanocrystals (NCs), which makes it difficult to achieve high-resolution X-ray imaging. 31,32 The third issue is that currently most scintillator devices are packaged with a simple mixture of powder scintillators and polymers, which makes it difficult to obtain high-quality and uniform scintillator films. 33−38 Based on this, the development of in-situ crystalline scintillator films can effectively solve the instability and packaging problems of copper-based metal halide and can also achieve flexible X-ray imaging.…”

Two‐Step Sequential Process for Fabricating Graphene Nanosheets Decorated with Copper Halide Nanocrystals and Their Optoelectronic Applications

“…Thus, developing nontoxic, luminescent nanocrystals that exhibit a greater stability while retaining their optoelectronic capabilities, unlike perovskite nanocrystals, is crucial. [ 17,18 ] Owing to their relatively low toxicity and earth‐abundant constituents, [ 19–21 ] Cs 3 Cu 2 X 5 ( X = I, Br, and Cl) nanocrystals have recently come under the spotlight as fascinating alternatives to lead halide perovskites. [ 20–22 ] In addition, these nanocrystals feature a unique self‐trapped exciton (STE) emission mechanism, [ 23,24 ] which results in a high quantum yield and emission stability.…”

“…Thus, developing nontoxic, luminescent nanocrystals that exhibit a greater stability while retaining their optoelectronic capabilities, unlike perovskite nanocrystals, is crucial. [17,18] Owing to their relatively low toxicity and earth-abundant constituents, [19][20][21] Cs 3 Cu 2 X 5 (X = I, Br, and Cl) nanocrystals have recently come under the spotlight as fascinating alternatives to lead halide perovskites. [20][21][22] In addition, these nanocrystals feature a unique self-trapped exciton (STE) emission mechanism, [23,24] which results in a high quantum yield and emission stability.…”

“…[17,18] Owing to their relatively low toxicity and earth-abundant constituents, [19][20][21] Cs 3 Cu 2 X 5 (X = I, Br, and Cl) nanocrystals have recently come under the spotlight as fascinating alternatives to lead halide perovskites. [20][21][22] In addition, these nanocrystals feature a unique self-trapped exciton (STE) emission mechanism, [23,24] which results in a high quantum yield and emission stability. [19,25] To date, significant efforts have been invested into utilizing the properties of nanoscale materials while retaining their stability for long durations through the use of a support.…”