Shining Emitter in a Stable Host: Design of Halide Perovskite Scintillators for X-ray Imaging from Commercial Concept

Crystal Growth of Quaternary AkRE2Si2S8 (Ak = Ca and Sr; RE = La-Tb) Thiosilicates Using Flux-Assisted Boron Chalcogen Mixture Method: Exploring X-ray Scintillation, Luminescence, and Magnetic Properties

We report on the detailed structural analysis of a series of 11 new quaternary rare earths containing thiosilicates, AkRE2Si2S8 (Ak = Ca and Sr; RE = La, Ce, Pr, Nd, Sm, Gd, and Tb), synthesized using the flux-assisted boron chalcogen mixture method. High quality crystals were grown and used to determine their crystal structures by single crystal X-ray diffraction. All members of the AkRE2Si2S8 series crystallize in the trigonal crystal system with space group R3̅c (space group no. 167). Polycrystalline powders were used for physical property measurements, including magnetic susceptibility, diffuse reflectance in the UV-visible range, and scintillation. Magnetic measurements indicated that CaRE2Si2S8 (RE = Nd and Tb) exhibits paramagnetic behavior with a slightly negative Weiss constant. The band gaps of the materials were determined from diffuse reflectance data, and optical band gaps were estimated to be 2.5(1) and 2.9(1) eV for CaCe2Si2S8 and CaGd2Si2S8, respectively. CaCe2Si2S8, CaTb2Si2S8, and SrCe2Si2S8 exhibited intense green luminescence upon irradiation with 375 nm ultraviolet light and, furthermore, scintillated when exposed to X-rays. Radioluminescence measurements of CaCe2Si2S8 powder revealed green emission with an intensity approximately 14% of that emitted by bismuth germanium oxide powder.

Organic Cation Modulation in Manganese Halides to Optimize Crystallization Process and X-Ray Response Toward Large-Area Scintillator Screen

Manganese halides are one of the most potential candidates for large-area flat-panel detection owing to their biological safety and all-solution preparation. However, reducing photon scattering and enhancing the efficient luminescence of scintillator screens remains a challenge due to their uncontrollable crystallization and serious nonradiative recombination. Herein, an organic cation modulation is reported to control the crystallization process and enhance the luminescence properties of manganese halides. Given the industrial requirements of the X-ray flat-panel detector, the large-area A2MnBr4 screen (900 cm2) with excellent uniformity is blade-coated at 60 °C. Theoretical calculations and in situ measurements reveal that organic cations with larger steric hindrance can slow down the crystallization of the screen, thus neatening the crystal arrangement and reducing the photon scattering. Moreover, larger steric hindrance can also endow the material with higher exciton binding energy, which is beneficial for restraining nonradiative recombination. Therefore, the BPP2MnBr4 (BPP = C25H22P+) screen with larger steric hindrance exhibits a superior spatial resolution (>20 lp mm-1) and ultra-low detection limit (< 250 nGyair s-1). This is the first time steric hindrance modulation is used in blade-coated scintillator screens, and it believes this study will provide some guidance for the development of high-performance manganese halide scintillators.

Large-Area Transparent Antimony-Based Perovskite Glass for High-Resolution X-ray Imaging

Nonlead low-dimensional halide perovskites attract considerable attention as X-ray scintillators. However, most scintillation screens exhibit pronounced light scattering, which detrimentally reduces the quality of X-ray imaging. Herein, we employed a simple and straightforward solvent-free melt-quenching method to fabricate a large-area zero-dimension (0D) antimony-based perovskite transparent medium, namely (C20H20P)2SbCl5 (C20H20P+ = ethyltriphenylphosphine). The transparency is due to the large steric hindrance of C20H20P+, which hinders the formation of crystals during the quenching process, thus forming a glass with low refractive index and uniform structure. This medium exhibits a high transmittance exceeding 80% in the range of 450-800 nm and shows a large Stokes shift of 245 nm, thereby minimizing light scattering, mitigating self-absorption, and enhancing the clarity of X-ray imaging. Moreover, it exhibits a high radioluminescence light yield of ∼12,535 photons MeV-1 and displays a high X-ray spatial resolution of 30 lp mm-1 owing to its high transparency. This study presents an alternative candidate for achieving high-quality X-ray detection and extends the applicability of transparent perovskite scintillators.

A Thermo-Responsive MOFs for X-Ray Scintillator

Thermo-responsive smart materials have aroused extensive interest due to the particular significance of temperature sensing. Although various photoluminescent materials are explored in thermal detection, it is not applicable enough in X-ray radiation environment where the accuracy and reliability will be influenced. Here, a strategy is proposed by introducing the concept of radio-luminescent functional building units (RBUs) to construct thermo-responsive lanthanide metal-organic frameworks (Ln-MOFs) scintillators for self-calibrating thermometry. The rational designs of RBUs (including organic ligand and Tb3+/Eu3+) with appropriate energy levels lead to high-performance radio-luminescence. Ln-MOFs scintillators exhibit perfect linear response to X-ray, presenting low dose rate detection limit (min ≈156.1 nGyairs-1). Self-calibrating detection based on ratiometric XEL intensities is achieved with good absolute and relative sensitivities of 6.74 and 8.1%K-1, respectively. High relative light yield (max ≈39000 photons MeV-1), imaging spatial resolution (max ≈18 lp mm-1), irradiation stability (intensity ≈100% at 368 K in total dose up to 215 Gyair), and giant color transformation visualization benefit the applications, especially the in situ thermo-responsive X-ray imaging. Such strategy provides a promising way to develop the novel smart photonic materials with excellent scintillator performances.

Cold-Sintered All-Inorganic Perovskite Bulk Composite Scintillators for Efficient X-ray Imaging

Cost-effective bulk scintillators with high density, large-area, and long-term stability are desirable for high-energy radiation detections. Conventional bulk polycrystalline or single-crystal scintillators are generally synthesized by high-temperature approaches, and it is challenging to realize simultaneously high detectivity/responsivity, spatial resolution, and rapid time response. Here, we report the cold sintering of bulk scintillators (at 90 °C) based on an "emitter-in-matrix" principle, in which emissive CsPbBr3 nanocrystals are embedded in a durable and transparent Cs4PbBr6 matrix. These bulk scintillators exhibit high light yield (33,800 photons MeV-1), low detection limit (79 nGyair s-1), fast decay time (9.8 ns), and outstanding spatial resolution of 8.9 lp mm-1 to X-ray radiation and an energy resolution of 19.3% for γ-ray (59.6 keV) detection. The composite scintillator also shows exceptional stability against environmental degradation and cyclic X-ray radiation. Our results demonstrate a cost-effective strategy for developing perovskite-based bulk transparent scintillators with exceptional performance and high radioluminescence stability for high-energy radiation detection and imaging.

Cs2NaGdCl6:Tb3+─A Highly Luminescent Rare-Earth Double Perovskite Scintillator for Low-Dose X-ray Detection and Imaging

Rare-earth-based double perovskite (DP) X-ray scintillators have gained significant importance with low detection limits in medical imaging and radiation detection owing to their high light yield (LY) and remarkable spatial resolution. Herein, we report the synthesis of 3D double perovskite (DP) crystals, namely, Cs2NaGdCl6 and Tb3+-Cs2NaGdCl6 using hydrothermal reaction. Cs2NaGdCl6 DP single crystals exhibited a blue self-trapped exciton (STE) emission at 470 nm under ultraviolet (265 nm) excitation with a photoluminescence quantum yield (PLQY) of 8.4%. Introducing Tb3+ ions into Cs2NaGdCl6 has resulted in quenching of STE emission and enhancing green emission at 549 nm attributed to the 5D4 → 7F5 transition of Tb3+, suggesting efficient energy transfer (ET) from STE to Tb3+. This ET process is evidenced by the appearance of Tb3+ bands in the excitation spectra of the host, the shortening of the STE lifetimes in the presence of Tb3+ ions, and the enhancement of PLQY (72.6%). Furthermore, Cs2NaGdCl6:5%Tb3+ films of various thicknesses (0.1-0.6 mm) were synthesized and their X-ray scintillating performance has been examined. The Cs2NaGdCl6:5%Tb3+ film with 0.4 mm thickness has exhibited an excellent linear response to the X-ray dose rate with a low detection limit of 41.32 nGyair s-1, an LY of 39,100 photons MeV-1, and excellent radiation stability. Benefiting from the strong X-ray excited luminescence (XEL) of Cs2NaGdCl6:5%Tb3+, we developed a Cs2NaGdCl6:5%Tb3+ X-ray scintillator screen with a least thickness (0.1 mm), exhibiting remarkable imaging ability with a spatial resolution of 10.75 lp mm-1. These results suggest that Cs2NaGdCl6:Tb3+ can be a potential candidate for low-dose and X-ray imaging applications.

Turning Nonemissive CsPb2Br5 Crystals into High-Performance Scintillators through Alkali Metal Doping

X-ray scintillators have utility in radiation detection, therapy, and imaging. Various materials, such as halide perovskites, organic illuminators, and metal clusters, have been developed to replace conventional scintillators due to their ease of fabrication, improved performance, and adaptability. However, they suffer from self-absorption, chemical instability, and weak X-ray stopping power. Addressing these limitations, we employ alkali metal doping to turn nonemissive CsPb2Br5 into scintillators. Introducing alkali metal dopants causes lattice distortion and enhances electron-phonon coupling, which creates transient potential energy wells capable of trapping photogenerated or X-ray-generated electrons and holes to form self-trapped excitons. These self-trapped excitons undergo radiative recombination, resulting in a photoluminescence quantum yield of 55.92%. The CsPb2Br5-based X-ray scintillator offers strong X-ray stopping power, high resistance to self-absorption, and enhanced stability when exposed to the atmosphere, chemical solvents, and intense irradiation. It exhibits a detection limit of 162.3 nGyair s-1 and an imaging resolution of 21 lp mm-1.

All-inorganic lead halide perovskites for photocatalysis: a review

Nowadays, environmental pollution and the energy crisis are two significant concerns in the world, and photocatalysis is seen as a key solution to these issues. All-inorganic lead halide perovskites have been extensively utilized in photocatalysis and have become one of the most promising materials in recent years. The superior performance of all-inorganic lead halide perovskites distinguish them from other photocatalysts. Since pure lead halide perovskites typically have shortcomings, such as low stability, poor active sites, and ineffective carrier extraction, that restrict their use in photocatalytic reactions, it is crucial to enhance their photocatalytic activity and stability. Huge progress has been made to deal with these critical issues to enhance the effects of all-inorganic lead halide perovskites as efficient photocatalysts in a wide range of applications. In this manuscript, the synthesis methods of all-inorganic lead halide perovskites are discussed, and promising strategies are proposed for superior photocatalytic performance. Moreover, the research progress of photocatalysis applications are summarized; finally, the issues of all-inorganic lead halide perovskite photocatalytic materials at the current state and future research directions are also analyzed and discussed. We hope that this manuscript will provide novel insights to researchers to further promote the research on photocatalysis based on all-inorganic lead halide perovskites.

Yellow Emissive CsCu2I3 Nanocrystals Induced by Mn2+ for High-Resolution X-ray Imaging

Recently, low-dimensional copper(I)-based perovskite or derivatives have gained extensive attention in scintillator applications because of their environmental friendliness and good stabilities. However, the unsatisfactory scintillation performance and complex fabrication processes hindered their practical applications. Herein, efficient yellow emissive CsCu2I3 nanocrystals (NCs) were successfully prepared via a simple Mn2+-assisted hot-injection method. The added Mn2+ effectively induced the phase transformation from Cs3Cu2I5 to CsCu2I3, leading to the preparation of single-phase CsCu2I3 NCs with few defects and a high fluorescence performance. The as-prepared "optimal CsCu2I3 NCs" exhibited superior photoluminescence (PL) performance with a record-high PL quantum yield (PLQY) of 61.9%. The excellent fluorescence originated from the radiative recombination of strongly localized one-dimension (1D) self-trapped excitons (STEs), which was systematically investigated via the wavelength-dependent PL excitation, PL emission, and temperature-dependent PL spectra. These CsCu2I3 NCs also exhibited outstanding X-ray scintillation properties with a high light yield (32000 photons MeV-1) and an ultralow detection limit (80.2 nGyair s-1). Eventually, the CsCu2I3 NCs scintillator film achieved an ultrahigh (16.6 lp mm-1) spatial resolution in X-ray imaging. The CsCu2I3 NCs also exhibited good stabilities against X-ray irradiation, heat, and environmental storage, indicating their great application potential in flexible X-ray detection and imaging.

Perovskite Scintillators for Improved X-ray Detection and Imaging

Halide perovskites (HPs) recently have emerged as one class of competitive scintillators for X-ray detection and imaging owing to its high quantum efficiency, short decay time, superior X-ray absorption capacity, low cost, and ease of crystal growth. The tunable structure and versatile chemical compositions of halide perovskites provide distinguishable advantages over traditional inorganic scintillators for optimizing scintillation performance. Since the first observation of the scintillation phenomenon in HPs, substantial efforts have been devoted to expanding the inventory of HP scintillators and regulating material properties. Understanding the relationship between the structure and scintillation properties of HP scintillators is essential for developing materials with improved X-ray detection and imaging capacities. This review summarizes strategies for improving the light yield of HP scintillators and provides a roadmap for improving the X-ray imaging performance. Additionally, methods for controlling the light propagation direction in HP scintillators are highlighted for improving X-ray imaging resolution. Finally, we highlight the current challenge in HP scintillators and provide a perspective on the future development of this emerging scintillator.

Surfactant-Dependent Bulk Scale Mechanochemical Synthesis of CsPbBr3 Nanocrystals for Plastic Scintillator-Based X-ray Imaging

We report a facile, solvent-free surfactant-dependent mechanochemical synthesis of highly luminescent CsPbBr3 nanocrystals (NCs) and study their scintillation properties. A small amount of surfactant oleylamine (OAM) plays an important role in the two-step ball milling method to control the size and emission properties of the NCs. The solid-state synthesized perovskite NCs exhibit a high photoluminescence quantum yield (PLQY) of up to 88% with excellent stability. CsPbBr3 NCs capped with different amounts of surfactant were dispersed in toluene and mixed with polymethyl methacrylate (PMMA) polymer and cast into scintillator discs. With increasing concentration of OAM during synthesis, the PL yield of CsPbBr3/PMMA nanocomposite was increased, which is attributed to reduced NC aggregation and PL quenching. We also varied the perovskite loading concentration in the nanocomposite and studied the resulting emission properties. The most intense PL emission was observed from the 2% perovskite-loaded disc, while the 10% loaded disc exhibited the highest radioluminescence (RL) emission from 50 kV X-rays. The strong RL yield may be attributed to the deep penetration of X-rays into the composite, combined with the large interaction cross-section of the X-rays with the high-Z atoms within the NCs. The nanocomposite disc shows an intense RL emission peak centered at 536 nm and a fast RL decay time of 29.4 ns. Further, we have demonstrated the X-ray imaging performance of a 10% CsPbBr3 NC-loaded nanocomposite disc.

Efficient X-ray luminescence imaging with ultrastable and eco-friendly copper(I)-iodide cluster microcubes

The advancement of contemporary X-ray imaging heavily depends on discovering scintillators that possess high sensitivity, robust stability, low toxicity, and a uniform size distribution. Despite significant progress in this field, the discovery of a material that satisfies all of these criteria remains a challenge. In this study, we report the synthesis of monodisperse copper(I)-iodide cluster microcubes as a new class of X-ray scintillators. The as-prepared microcubes exhibit remarkable sensitivity to X-rays and exceptional stability under moisture and X-ray exposure. The uniform size distribution and high scintillation performance of the copper(I)-iodide cluster microcubes make them suitable for the fabrication of large-area, flexible scintillating films for X-ray imaging applications in both static and dynamic settings.

Self-wavelength shifting in two-dimensional perovskite for sensitive and fast gamma-ray detection

Lead halide perovskites have recently emerged as promising X/γ-ray scintillators. However, the small Stokes shift of exciton luminescence in perovskite scintillators creates problems for the light extraction efficiency and severely impedes their applications in hard X/γ-ray detection. Dopants have been used to shift the emission wavelength, but the radioluminescence lifetime has also been unwantedly extended. Herein, we demonstrate the intrinsic strain in 2D perovskite crystals as a general phenomenon, which could be utilized as self-wavelength shifting to reduce the self-absorption effect without sacrificing the radiation response speed. Furthermore, we successfully demonstrated the first imaging reconstruction by perovskites for application of positron emission tomography. The coincidence time resolution for the optimized perovskite single crystals (4 × 4 × 0.8 mm³) reached 119 ± 3 ps. This work provides a new paradigm for suppressing the self-absorption effect in scintillators and may facilitate the application of perovskite scintillators in practical hard X/γ-ray detections.

High-Efficiency ZnS: Cu+, Al3+ Scintillator for X-ray Detection in a Non-Darkroom Environment

Scintillator is a key component in X-ray detectors that determine the performance of the devices. Nevertheless, due to the interference of the ambient light sources, scintillators are only operated in a darkroom environment currently. In this study, we designed a Cu⁺ and Al³⁺ co-doped ZnS scintillator (ZnS: Cu⁺, Al³⁺) that introduces donor-acceptor (D-A) pairs for X-ray detection. The prepared scintillator displayed an extremely high steady-state light yield (53,000 photons per MeV) upon X-ray irradiation, which is 5.3 times higher than that of the commercial Bi₄Ge₃O₁₂ (BGO) scintillator, making it possible in X-ray detection with the interference of ambient light. Furthermore, the prepared material was employed as a scintillator to construct an indirect X-ray detector, which performed a superior spatial resolution (≈10.0 lp/mm) as well as persistent stability under visible light interference, demonstrating the feasibility of the scintillator in practical applications. Therefore, this research presented a convenient and useful strategy to realize X-ray detection in a non-darkroom environment.

Compositional gradient engineering and applications in halide perovskites

Organic-inorganic halide perovskites (HPs) have attracted respectable interests as active layers in solar cells, light-emitting diodes, photodetectors, etc. Besides the promising optoelectronic properties and solution-processed preparation, the soft lattice in HPs leads to flexible and versatile compositions and structures, providing an effective platform to regulate the bandgaps and optoelectronic properties. However, conventional solution-processed HPs are homogeneous in composition. Therefore, it often requires the cooperation of multiple devices in order to achieve multi-band detection or emission, which increases the complexity of the detection/emission system. In light of this, the construction of a multi-component compositional gradient in a single active layer has promising prospects. In this review, we summarize the gradient engineering methods for different forms of HPs. The advantages and limitations of these methods are compared. Moreover, the entropy-driven ion diffusion favors compositional homogeneity, thus the stability issue of the gradient is also discussed for long-term applications. Furthermore, applications based on these compositional gradient HPs will also be presented, where the gradient bandgap introduced therein can facilitate carrier extraction, and the multi-components on one device facilitate functional integration. It is expected that this review can provide guidance for the further development of gradient HPs and their applications.

Recent Development of Halide Perovskite Materials and Devices for Ionizing Radiation Detection

Ionizing radiation such as X-rays and γ-rays has been extensively studied and used in various fields such as medical imaging, radiographic nondestructive testing, nuclear defense, homeland security, and scientific research. Therefore, the detection of such high-energy radiation with high-sensitivity and low-cost-based materials and devices is highly important and desirable. Halide perovskites have emerged as promising candidates for radiation detection due to the large light absorption coefficient, large resistivity, low leakage current, high mobility, and simplicity in synthesis and processing as compared with commercial silicon (Si) and amorphous selenium (a-Se). In this review, we provide an extensive overview of current progress in terms of materials development and corresponding device architectures for radiation detection. We discuss the properties of a plethora of reported compounds involving organic-inorganic hybrid, all-inorganic, all-organic perovskite and antiperovskite structures, as well as the continuous breakthroughs in device architectures, performance, and environmental stability. We focus on the critical advancements of the field in the past few years and we provide valuable insight for the development of next-generation materials and devices for radiation detection and imaging applications.

Color-Tunable and Stable Copper Iodide Cluster Scintillators for Efficient X-Ray Imaging

The search for color-tunable, efficient, and robust scintillators plays a vital role in the development of modern X-ray radiography. The radioluminescence tuning of copper iodide cluster scintillators in the entire visible region by bandgap engineering is herein reported. The bandgap engineering benefits from the fact that the conduction band minimum and valence band maximum of copper iodide cluster crystals are contributed by atomic orbitals from the inorganic core and organic ligand components, respectively. In addition to high scintillation performance, the as-prepared crystalline copper iodide cluster solids exhibit remarkable resistance toward both moisture and X-ray irradiation. These features allow copper iodide cluster scintillators to show particular attractiveness for low-dose X-ray radiography with a detection limit of 55  nGy s^-1 , a value ≈100 times lower than a standard dosage for X-ray examinations. The results suggest that optimizing both inorganic core and organic ligand for the building blocks of metal halide cluster crystals may provide new opportunities for a new generation of high-performance scintillation materials.

Highly Efficient, Flexible, and Eco-Friendly Manganese(II) Halide Nanocrystal Membrane with Low Light Scattering for High-Resolution X-ray Imaging

Scintillators enable invisible X-ray to be converted into ultraviolet (UV)/visible light that can be collected using a sensor array and is the core component of the X-ray imaging system. However, combining the excellent properties of high light output, high spatial resolution, flexibility, non-toxicity, and cost effectiveness into a single X-ray scintillator remains a great challenge. Herein, a novel scintillator based on benzyltriphenylphosphonium manganese(II) bromide (BTP₂MnBr₄) nanocrystal (NC) membranes was developed by the in situ fabrication strategy. The long Mn-Mn distance provided by the large BTP cation allows the nonradiative energy dissipation in this manganese(II) halide to be significantly suppressed. As a result, the flexible BTP₂MnBr₄ NC scintillator shows an excellent linear response to the X-ray dose rate, a high light yield of ∼71,000 photon/MeV, a low detection limit of 86.2 nGy_air/s at a signal-to-noise ratio of 3, a strong radiation hardness, and a long-term thermal stability. Thanks to the low Rayleigh scattering associated with the dense distribution of nanometer-scale emitters, light cross-talk in X-ray imaging is greatly suppressed. The impressively high-spatial resolution X-ray imaging (23.8 lp/mm at modulation transfer function = 0.2 and >20 lp/mm for a standard pattern chart) was achieved on this scintillator. Moreover, well-resolved 3D dynamic rendering X-ray projections were also successfully demonstrated using this scintillator. These results shed light on designing efficient, flexible, and eco-friendly scintillators for high-resolution X-ray imaging.

Contribución de la radiología digital al mejoramiento de la calidad en el servicio de imagenología

Objetivo. El presente estudio documental evalúa las estrategias óptimas de la radiología digital (DR) en los servicios de Radiología en los hospitales de baja y mediana complejidad en Colombia. Método. Revisión bibliográfica exhaustiva donde se identificó los beneficios y se hizo comparación con la radiología análoga, se desarrolló basado en una muestra de 32 artículos científicos en diferentes revistas como Dialnet, SciELO, Scopus, Springer Open, IOP Science. Resultado. La imagen por rayos X es una tecnología poderosa y de bajo costo que se ha utilizado ampliamente en el diagnóstico médico. La importancia tecnológica de las imágenes de rayos X ha llevado al rápido desarrollo de detectores de rayos X de alto rendimiento y las aplicaciones de imágenes asociadas. Por lo tanto, los servicios de imágenes médicas proponen estrategias efectivas en la funcionalidad de la radiología digital, factores que interfieren con el proceso del sistema informático. Conclusión. Teniendo en cuenta los avances técnicos y fundamentales de los detectores de rayos X, el surgimiento de la radiografía computarizada (CR) (DR) ha llevado a la evolución tecnológica para la obtención de imágenes de rayos X digitales con información más precisa e instantánea, mientras que su mecanismode lectura separado adolece de limitaciones técnicas, como una alta dosis de radiación y una imagen no dinámica, esto permite a los prestadores de servicio de imagenología se motiven a invertir en una tecnología adecuada para generar un aprovechamiento más óptimo de los recursos y el servicio sea prestado al paciente con alta calidad.

Halide Perovskite: A Promising Candidate for Next-Generation X-Ray Detectors

In the past decade, metal halide perovskite (HP) has become a superstar semiconductor material due to its great application potential in the photovoltaic and photoelectric fields. In fact, HP initially attracted worldwide attention because of its excellent photovoltaic efficiency. However, HP and its derivatives also show great promise in X-ray detection due to their strong X-ray absorption, high bulk resistivity, suitable optical bandgap, and compatibility with integrated circuits. In this review, the basic working principles and modes of both the direct-type and the indirect-type X-ray detectors are first summarized before discussing the applicability of HP for these two types of detection based on the pros and cons of different perovskites. Furthermore, the authors expand their view to different preparation methods developed for HP including single crystals and polycrystalline materials. Upon systematically analyzing their potential for X-ray detection and photoelectronic characteristics on the basis of different structures and dimensions (0D, 2D, and 3D), recent progress of HPs (mainly polycrystalline) applied to flexible X-ray detection are reviewed, and their practicability and feasibility are discussed. Finally, by reviewing the current research on HP-based X-ray detection, the challenges in this field are identified, and the main directions and prospects of future research are suggested.

Mechanochemistry-driven engineering of 0D/3D heterostructure for designing highly luminescent Cs–Pb–Br perovskites

Embedding metal-halide perovskite particles within an insulating host matrix has proven to be an effective strategy for revealing the outstanding luminescence properties of perovskites as an emerging class of light emitters. Particularly, unexpected bright green emission observed in a nominally pure zero-dimensional cesium–lead–bromide perovskite (Cs₄PbBr₆) has triggered intensive research in better understanding the serendipitous incorporation of emissive guest species within the Cs₄PbBr₆ host. However, a limited controllability over such heterostructural configurations in conventional solution-based synthesis methods has limited the degree of freedom in designing synthesis routes for accessing different structural and compositional configurations of these host–guest species. In this study, we provide means of enhancing the luminescence properties in the nominal Cs₄PbBr₆ powder through a guided heterostructural configuration engineering enabled by solid-state mechanochemical synthesis. Realized by an in-depth study on time-dependent evaluation of optical and structural properties during the synthesis of Cs₄PbBr₆, our target-designed synthesis protocol to promote the endotaxial formation of Cs₄PbBr₆/CsPbBr₃ heterostructures provides key insights for understanding and designing kinetics-guided syntheses of highly luminescent perovskite emitters for light-emitting applications.

While emission and stability of metal–halide perovskites can be enhanced through heterostructural encapsulation, a controlled synthesis route to such structures is not trivial to realize. Here, the authors design a mechanochemistry-driven protocol for synthesizing highly luminescent CsPbBr₃/Cs₄PbBr₆ heterostructures.

Copper-based metal halides for X-ray and photodetection

Copper-based metal halides have become important materials in the field of X-ray and photodetection due to their excellent optical properties, good environmental stability and low toxicity. This review presents the progress of research on crystal structure/morphology, photophysics/optical properties and applications of copper-based metal halides. We also discuss the challenges of copper-based metal halides with a perspective of their future research directions.

Thermally Activated Delayed Fluorescence Zirconium-Based Perovskites for Large-Area and Ultraflexible X-ray Scintillator Screens

Flexible scintillator screens with environmental stability, high sensitivity, and low cost have emerged as candidates for X-ray imaging applications. Here, a large-scale and cost-efficient solution synthesis of the vacancy-ordered double perovskite Cs₂ ZrCl₆ , which is characterized by thermal activation delayed fluorescence (TADF) dominated by triplet emission under X-ray irradiation, is demonstrated. The large Stokes shift and efficient luminescence collection of TADF effectively ensure the light outcoupling efficiency. Further, flexible X-ray scintillator screens with an area of 400 cm² are prepared using poly(dimethylsiloxane) (PDMS) as the carrier, exhibiting excellent scintillation properties with light yields as high as 49 400 photons MeV^-1 , spatial resolutions up to 18 lp mm^-1 and detection limits as low as 65 nGy s^-1 . Finally, the high-quality imaging results of non-planar and dynamic objects by such screens are demonstrated. It is believed that the explored Cs₂ ZrCl₆ @PDMS flexible scintillator screens would offer a big step toward expanding the application range of scintillators in different environments.

Application of perovskites in bioimaging: the state-of-the-art and future developments

BACKGROUND

Recently, the development of perovskite-based nanocrystals for sustainable applications in bioimaging and clinical diagnostics have become a very active area of research. From 2D hybrid to zero-dimensional quantum dots (QDs), perovskites along with a variety of characteristic features, specifically non-linear optoelectronics properties, have attracted enormous research attention. These characteristics can be tuned by the type of cations or anions and their ratio used in host perovskites. Carrier doping and chemical modifications are additional alternatives to control optical and magnetism in radiodiagnostics.

AREA COVERED

This review begins by explaining the physical phenomena associated with luminescence or optical features of novel perovskites in diagnostic applications. Moreover, reported oxide, halide, doped, and QDs-based nanoprobes were elaborated. At last, the need for novel perovskite development, for example, persistent luminescent and low cytotoxicity is discussed, and the futuristic perspective of perovskites in clinical diagnostics with real-time demonstration is explained.

EXPERT OPINION

Our article concludes that hybrid perovskites, including metal-free, core-shell nanocomposites-based, and alloy-based perovskites, exhibit tunable bandgap and high photoluminescence quantum yields which ultimately result in high optical features. However, given limited understanding of ion transport mechanisms and dependency on environmental conditions of the perovskites, more research is needed.

Temperature dependent scintillation properties and mechanisms of (PEA)2PbBr4 single crystals

In this work the scintillation properties of PEA₂PbBr₄ are studied as function of temperature, accessing the potential use of these materials for low temperature applications. The scintillation properties and mechanism have been studied using a combination of temperature dependent photoluminescence emission and excitation, X-ray excited emission and decay measurements. At room temperature the X-ray excited emission is dominated by the 442 nm emission with a lifetime of 35.2 ns. Under UV-Vis photon excitation an additional emission peak is observed at 412 nm. At 10 K, both X-ray and UV-Vis photon excited emission spectra show a narrow emission peak at 412 nm and a broad emission band centred around 525 nm with a lifetime of 1.53 ns (24%) and 154 ns (76%) respectively. The exact nature of the observed emission peaks is not known. For this reason two potential mechanisms explaining the difference between UV-Vis photon and X-ray excitation and their temperature dependent emissions are explored. The total spectral intensity decreases to 72% of the intensity at room temperature at 10 K. It is suggested that the observed negative thermal quenching behaviour results from a combination of more self absorption and a higher degree of self trapped exciton formation under X-ray excitation. Based on the observed fast decay component at 10 K and light yield of 9400 photons per MeV at room temperature, showing only a 28% decrease at 10 K, could make this material potentially interesting for low temperature and fast timing applications.

Stable and Bright Electroluminescent Devices utilizing Emissive 0D Perovskite Nanocrystals Incorporated in a 3D CsPbBr3 Matrix

The 0D cesium lead halide perovskite Cs₄ PbBr₆ has drawn remarkable interest due to its highly efficient robust green emission compared to its 3D CsPbBr₃ counterpart. However, seizing the advantages of the superior photoluminescence properties for practical light-emitting devices remains elusive. To date, Cs₄ PbBr₆ has been employed only as a higher-bandgap nonluminescent matrix to passivate or provide quantum/dielectric confinement to CsPbBr₃ in light-emitting devices and to enhance its photo-/thermal/environmental stability. To resolve this disparity, a novel solvent engineering method to incorporate highly luminescent 0D Cs₄ PbBr₆ nanocrystals (perovskite nanocrystals (PNCs)) into a 3D CsPbBr₃ film, forming the active emissive layer in single-layer perovskite light-emitting electrochemical cells (PeLECs) is designed. A dramatic increase of the maximum external quantum efficiency and luminance from 2.7% and 6050 cd m^-2 for a 3D-only PeLEC to 8.3% and 11 200 cd m^-2 for a 3D-0D PNC device with only 7% by weight of 0D PNCs is observed. The majority of this increase is driven by the efficient inherent emission of the 0D PNCs, while the concomitant morphology improvement also contributes to reduced leakage current, reduced hysteresis, and enhanced operational lifetime (half-life of 129 h), making this one of the best-performing LECs reported to date.

Efficient Near-Infrared Luminescence in Lanthanide-Doped Vacancy-Ordered Double Perovskite Cs2 ZrCl6 Phosphors via Te4+ Sensitization

All-inorganic lead-free perovskite-derivative metal halides have shown great promise in optoelectronics, however, it remains challenging to realize efficient near-infrared (NIR) luminescence in these materials. Herein, we report a novel strategy based on Te⁴⁺ /Ln³⁺ (Ln=Er, Nd, and Yb) co-doping to achieve efficient NIR luminescence in vacancy-ordered double perovskite Cs₂ ZrCl₆ phosphors, which are excitable by a low-cost near-ultraviolet light-emitting diode (LED) chip. Through sensitization by the spin-orbital allowed ¹ S₀ →³ P₁ transition of Te⁴⁺ , intense and multi-wavelength NIR luminescence originating from the 4f→4f transitions of Er³⁺ , Nd³⁺ , and Yb³⁺ was acquired, with a quantum yield of 6.1 % for the Er³⁺ emission. These findings provide a general approach to achieve efficient NIR emission in lead-free metal halides through ns² -metal and lanthanide ion co-doping, thereby opening up a new avenue for exploring NIR-emitting perovskite derivatives towards versatile applications such as NIR-LEDs and bioimaging.

Interlayer-Assisted Growth of Si-Based All-Inorganic Perovskite Films via Chemical Vapor Deposition for Sensitive and Stable X-ray Detection

All-inorganic perovskites are considered as preferred materials for next-generation X-ray detectors. However, preparing high-quality thick films by traditional solution-based methods remains challenging due to the low solubility of the precursors. In this work, chemical vapor deposition technology is employed to grow Si-based all-inorganic cesium-lead-bromide perovskite thick films. By introducing a SnO₂ nanocrystal interlayer onto the Si substrate to facilitate the heterogeneous nucleation of the perovskite, we are able to grow high-quality films with a smooth surface and compact grains at a relatively low substrate temperature of 260 °C. The resultant X-ray detectors exhibit a decent sensitivity of 2930 μC Gy_air^-1 cm^-2, a small dark current density of 1.5 nA cm^-2, and a low detection limit of 120 nGy_air s^-1. Moreover, the devices show excellent biasing stability with a record small baseline drift of 4.6 × 10^-9 nA cm^-1 s^-1 V^-1 under a large electric field of 1100 V/cm among all perovskite polycrystalline film-based detectors ever reported.

Formation mechanisms of CsPbBr3/Cs4PbBr6 microscale composites assisted with imidazolium cations and their device applications

The instability of all-inorganic perovskite nanocrystals (NCs) remains a major challenge to their practical applications in displays and lighting. In order to improve their environmental resistance, highly luminescent CsPbBr₃ NC embedded Cs₄PbBr₆ microcrystals (MCs) have been fabricated by an anti-solvent reprecipitation method with the assistance of 1-alkyl-3-methyl-imidazolium bromides. The heterostructure of the MCs is investigated in detail, and their formation mechanism is discussed in terms of the dissolution-precipitation equilibria and the total energy of variously scaled nanoparticles via density functional theory (DFT) calculations. Although the imidazolium ligands are not directly capping with the inner CsPbBr₃ NCs, they are important to the formation of these MCs. The MCs exhibit better thermal resistance compared to conventional CsPbBr₃ NCs prepared by the hot-injection method. Additionally, a prototype white light-emitting diode (WLED) was fabricated to demonstrate its practical application prospects. Thanks to the narrow emission bands and enhanced stability of the MCs, the WLED shows greater performance compared to bare perovskite NCs, indicating its great potential as a green phosphor in lighting and display applications.

Metal-Free PAZE-NH4 X3 ⋅H2 O Perovskite for Flexible Transparent X-ray Detection and Imaging

Metal-free perovskites are of interest for their chemical diversity and eco-friendly properties, and recently have been used for X-ray detection with superior carrier behavior. However, the size and shape complexity of the organic components results in difficulties in evaluating their stability in high-energy radiation. Herein, we introduce multiple hydrogen-bond metal-free PAZE-NH₄ X₃ ⋅H₂ O perovskite, where H₂ O leads to more hydrogen bonds appearing between organic molecules and the perovskite host. As suggested by the theoretical calculations, multiple hydrogen bonds promote stiffness of the lattice, and increase the diffusion barrier to inhibit ionic migration. Then, low trap density, high μτ products and structural flexibility of PAZE-NH₄ Br₃ ⋅H₂ O give a flexible X-ray detector with the highest sensitivity of 3708 μC Gy_air ^-1  cm^-2 , ultra-low detection limit of 0.19 μGy_air ^-1  s^-1 and superior spatial resolution of 5.0 lp mm^-1 .

Ultrathin, Transparent, and High Density Perovskite Scintillator Film for High Resolution X-Ray Microscopic Imaging

Inorganic perovskite quantum dots CsPbX₃ (X = Cl, Br, and I) has recently received extensive attention as a new promising class of X-ray scintillators. However, relatively low light yield (LY) of CsPbX₃ and strong optical scattering of the thick opaque scintillator film restrict their practical applications for high-resolution X-ray microscopic imaging. Here, the Ce³⁺ ion doped CsPbBr₃ nanocrystals (NCs) with enhanced LY and stability are obtained and then the ultrathin (30 µm) and transparent scintillator films with high density are prepared by a suction filtration method. The small amount Ce³⁺ dopant greatly enhances the LY of CsPbBr₃ NCs (about 33 000 photons per MeV), which is much higher than that of bare CsPbBr₃ NCs. Moreover, the scintillator films made by these NCs with high density realize a high spatial resolution of 862 nm thanks to its thin and transparent feature, which is so far a record resolution for perovskite scintillator-based X-ray microscopic imaging. This strategy not only provides a simple way to increase the resolution down to nanoscale but also extends the application of as-prepared CsPbBr₃ scintillator for high resolution X-ray microscopic imaging.

Spontaneous Formation of Lead-Free Cs3 Cu2 I5 Quantum Dots in Metal-Organic-Frameworks with Deep-Blue Emission

All-inorganic lead-free Cs₃ Cu₂ I₅  perovskite-derivant quantum dots (QDs) have attracted tremendous attention due to their nontoxicity and unique optoelectronic properties. However, the traditional hot-injection method requires high temperatures and multiple ligands to confine the growth of QDs. Herein, a strategy is reported to spontaneously synthesize ultrasmall Cs₃ Cu₂ I₅  QDs within metal-organic-frameworks (MOFs) MOF-74 at room temperature (RT) with an average diameter of 4.33 nm. The obtained Cs₃ Cu₂ I₅  QDs exhibit an evident deep-blue emission with Commission Internationale de L'Eclairage coordinates of (0.17, 0.07), owing to the strong quantum confinement effect. Due to the protection of MOF-74, the Cs₃ Cu₂ I₅  QDs demonstrate superior stability, and the photoluminescence quantum yield retains 89% of the initial value after the storage of 1440 h under the environment with relative humidity exceeding 70%. Besides, triplet-triplet annihilation upconversion emission is observed within the composite of Cs₃ Cu₂ I₅ @MOF-74, which brings out apparent temperature-dependent photoluminescence. This study reveals a facile method for fabricating ultrasmall lead-free perovskite-derivant QDs at RT without multiple ligands. Besides, the temperature-dependent photoluminescence of Cs₃ Cu₂ I₅ @MOF-74 may open up a new way to develop the applications of temperature sensors or other related optoelectronic devices.

Organic-Inorganic Hybrid Cuprous Halide Scintillators for Flexible X-ray Imaging

Recently, organic-inorganic hybrid scintillators have received more and more attention because of their merits of easy preparation, good stability, and nontoxicity. Considering the high cost of traditional inorganic scintillators, here we describe experimental investigations of a low-cost zero-dimensional scintillator comprising organic-inorganic hybrid cuprous halide and its capabilities for sensitive X-ray detection and flexible X-ray imaging. This scintillator is synthesized using a facile antisolvent diffusion method with large scalability (50 g). The crystal structure shows an unreported plane rhombus cuprous halide core, which also demonstrates outstanding photoluminescence with a high quantum yield (99.5%), excellent radioluminescence with an efficient internal light yield (25 000 photon/MeV), and sensitive X-ray response with a low detection limit (40.4 nGy/s). The organic-inorganic hybrid chemical feature allows the fabrication of a flexible film based on this scintillator for fine-resolution X-ray radiography. These advantages endow our organic-inorganic hybrid scintillator with promising potential in wearable and portable medical devices.

Recent advances in lead-free double perovskites for x-ray and photodetection

Over the last decade, lead halide perovskites have attracted significant research attention in the field of photovoltaics, light-emitting devices, photodetection, ionizing radiation detection, etc, owing to their outstanding optoelectrical properties. However, the commercial applications of lead-based perovskite devices are restricted due to the poor ambient stability and toxicity of lead. The encapsulation of lead-based devices can reduce the possible leakage of lead. However, it is hard to ensure safety during large-scale production and long-term storage. Recently, considerable efforts have been made to design lead-free perovskites for different optoelectronic applications. Metal halide double perovskites with the general formula of A₂M^IM^IIIX₆or A₂M^IVX₆could be potentially considered as green and stable alternatives for different optoelectronic applications. In this review article, we focus on the recent progress and findings on lead-free halide double perovskites for x-ray and UV-vis photodetection applications. Lead-free halide double perovskite has recently drawn a great deal of attention for superior x-ray detection due to its high absorption coefficient, large carrier mobility-lifetime product, and large bulk resistance. In addition, these materials exhibit good performance in photodetection in the UV-vis region due to high photocarrier generation and efficient carrier separation. In this review, first, we define the characteristics of lead-free double perovskite materials. The fundamental characteristics and beneficial properties of halide perovskites for direct and indirect x-ray detection are then discussed. We comprehensively review recent developments and efforts on lead-free double perovskite for x-ray detection and UV-vis photodetection. We bring out the current challenges and opportunities in the field and finally present the future outlook for developing lead-free double perovskite-based x-ray and UV-vis photodetectors for practical applications.

In Situ Fabrication of Cs3Cu2I5: Tl Nanocrystal Films for High-Resolution and Ultrastable X-ray Imaging

Cs₃Cu₂I₅ nanocrystals (NCs) are considered to be promising materials due to their high photoluminescence efficiency and X-ray hardness. However, the present strategy depends on tedious fabrication with excessive chemical waste. The evasive iodide ion dissociation, inadaptable ligand system, low stability, and relatively low light yield severely impede their applications. Herein, we develop an in situ fabrication strategy for a flexible and large-area Tl-doped Cs₃Cu₂I₅ NC-polymer composite scintillation film with a high light yield (∼48800 photons/MeV) and improved stability. Tween 80 and phosphinic acid successfully inhibit the oxidation of iodide ions, and the films can be stored for at least six months. As a result, a high spatial resolution of 16.3 lp mm^-1 and a low detection limit of 305 nGy_air s^-1 were achieved. A radioluminescence intensity of >80% was maintained after a total irradiation dose of 604.8 Gy. These results indicate the promising application of these copper halide NCs in low-cost, flexible, and high-performance medical imaging.

All-inorganic perovskite nanocrystals: next-generation scintillation materials for high-resolution X-ray imaging

With super strong penetrability, high-energy X-rays can be applied to probe the inner structure of target objects under nondestructive situations. Scintillation materials can down-convert X-rays into visible light, enabling the reception of photon signals and photoelectric conversion by common sensing arrays such as photomultiplier tubes and amorphous-Si photodiode matrixes. All-inorganic perovskite nanocrystals are emerging photovoltaic and scintillation materials, with tremendous light-conversion efficiency and tunable luminous properties, exhibiting great potential for high-quality X-ray imaging. Recent advancements in nanotechnology further accelerate the performance improvement of scintillation materials. In this review, we will provide a comprehensive overview of novel all-inorganic perovskite nano-scintillators in terms of potential applications in low-dose X-ray medical radiography. Compared with conventional scintillators, the merits/drawbacks, challenges, and scintillation performance control will be the focus of this article.

Single-Crystalline Perovskite Nanowire Arrays for Stable X-ray Scintillators with Micrometer Spatial Resolution

X-ray scintillation detectors based on metal halide perovskites have shown excellent light yield, but they mostly target applications with spatial resolution at the tens of micrometers level. Here, we use a one-step solution method to grow arrays of 15-μm-long single-crystalline CsPbBr₃ nanowires (NWs) in an AAO (anodized aluminum oxide) membrane template, with nanowire diameters ranging from 30 to 360 nm. The CsPbBr₃ nanowires in AAO (CsPbBr₃ NW/AAO) show increasing X-ray scintillation efficiency with decreasing nanowire diameter, with a maximum photon yield of ∼5 300 ph/MeV at 30 nm diameter. The CsPbBr₃ NW/AAO composites also display high radiation resistance, with a scintillation-intensity decrease of only ∼20-30% after 24 h of X-ray exposure (integrated dose 162 Gy_air) and almost no change after ambient storage for 2 months. X-ray images can distinguish line pairs with a spacing of 2 μm for all nanowire diameters, while slanted edge measurements show a spatial resolution of ∼160 lp/mm at modulation transfer function (MTF) = 0.1. The combination of high spatial resolution, radiation stability, and easy fabrication makes these CsPbBr₃ NW/AAO scintillators a promising candidate for high-resolution X-ray imaging applications.

Nanosecond and Highly Sensitive Scintillator Based on All-Inorganic Perovskite Single Crystals

The scintillator is a unique class of luminescent materials, which is of great significance in clinical diagnosis, security inspection, and radiation detection. Herein, an all-inorganic Cs₄PbI₆ single crystals (SCs) as a nanosecond and an efficient X-ray and α particle scintillator is described. The radioluminescence (RL) spectrum of Cs₄PbI₆ SCs under X-ray excitation consists of a band gap emission at 310 nm and a broadband emission at 552 nm at room temperature. Furthermore, Cs₄PbI₆ SCs demonstrate nanosecond decay times of 0.95 and 6.86 ns, a high sensitivity to low-energy X-ray (30 keV) with a low detection limit (187 nGy_air/s), and a favorable linearity detection range, potentially enabling their broad application in X-ray imaging. Under ²³⁷Np α particle irradiation, the light yield of Cs₄PbI₆ SCs is about 49.5% of that of a BGO scintillator with an energy resolution of 35% at 4.78 MeV. Our results demonstrate the potential of Cs₄PbI₆ SCs as a nanosecond and low-cost scintillator in radiation detection applications.

Template directed perovskite X-ray detectors towards low ionic migration and low interpixel cross talking

The metal halide perovskites exhibit excellent performance as the direct X-ray detectors owing to their strong absorption capability, long carrier lifetime and diffusion length, radiation ruggedness, etc. For imaging applications, the ionic migration of perovskites and charge sharing effect between the adjacent pixels have a significantly negative impact on the spatial resolution. Herein, for the first time, the porous anodic aluminum oxides (AAO) have been used as a template to grow the CsPbBr2I thick film for the direct X-ray detection. Benefiting from the oxygen passivation effect, the activation energy for ionic migration has been observed to increase to 0.701 eV, whereas the dark current drift (1.01 × 10-5 nA cm-1s-1V-1) is one to two orders of magnitude lower than the other lead halide perovskite single crystals and films. Moreover, the AAO insulating wall effectively blocks the charge diffusion effect across a pixel pitch of 10 μm. Overall, the findings reported in this study open a new route for reducing the ionic migration and pixel crosstalk, thus, bringing the perovskite X-ray detectors close to the practical applications.

Surface Chemistry Engineering of Perovskite Quantum Dots: Strategies, Applications, and Perspectives

The presence of surface ligands not only plays a key role in keeping the colloidal integrity and non-defective surface of metal halide perovskite quantum dots (PQDs), but also serves as a knob to tune their optoelectronic properties for a variety of exciting applications including solar cells and light-emitting diodes. However, these indispensable surface ligands may also deteriorate the stability and key properties of PQDs due to their highly dynamic binding and insulating nature. To address these issues, a number of innovative surface chemistry engineering approaches have been developed in the past few years. Based on an in-depth fundamental understanding of the surface atomistic structure and surface defect formation mechanism in the tiny nanoparticles, a critical overview focusing on the surface chemistry engineering of PQDs including advanced colloidal synthesis, in-situ surface passivation, and solution-phase/solid-state ligand exchange is presented, after which their unprecedented achievements in photovoltaics and other optoelectronics are presented. The practical hurdles and future directions are critically discussed to inspire more rational design of PQD surface chemistry toward practical applications.

Recent Development in X-Ray Imaging Technology: Future and Challenges

X-ray imaging is a low-cost, powerful technology that has been extensively used in medical diagnosis and industrial nondestructive inspection. The ability of X-rays to penetrate through the body presents great advances for noninvasive imaging of its internal structure. In particular, the technological importance of X-ray imaging has led to the rapid development of high-performance X-ray detectors and the associated imaging applications. Here, we present an overview of the recent development of X-ray imaging-related technologies since the discovery of X-rays in the 1890s and discuss the fundamental mechanism of diverse X-ray imaging instruments, as well as their advantages and disadvantages on X-ray imaging performance. We also highlight various applications of advanced X-ray imaging in a diversity of fields. We further discuss future research directions and challenges in developing advanced next-generation materials that are crucial to the fabrication of flexible, low-dose, high-resolution X-ray imaging detectors.

Highly efficient copper halide scintillators for high-performance and dynamic X-ray imaging

Progress towards high performance X-ray detection and dynamic imaging applications, including nondestructive inspection, homeland security, and medical diagnostics, requires scintillators with a high light yield, a reasonable decay time, low cost, and eco-friendliness. Recently, copper halide scintillators have drawn tremendous attention due to their outstanding radioluminescence performance. Here, we first employed β-Cs₃Cu₂Cl₅ as a high-performance scintillator, with a photoluminescence quantum yield (PLQY) of 94.6%, a radioluminescence light yield of 34 000 ± 4000 photons per MeV, a low detection limit of 81.7 nGy_air s^-1, and good operational stability under a total X-ray dose of 174.6 Gy_air in air. In addition, this scintillator presents a high spatial resolution of 9.6 lp mm^-1 at the modulation transfer function of 0.2 and a superb performance at 60 frames per second in our X-ray imaging system. Overall, this highly efficient scintillator demonstrates outstanding comprehensive performance and shows great potential for broad applications in X-ray detection and dynamic imaging.

PbI2-TiO2 Bulk Heterojunctions with Long-Range Ordering for X-ray Detectors

High-performance X-ray detectors are usually based on single crystals, due to the long-range ordering and hence outstanding electronic properties. On the other hand, bulk heterojunctions (BHJs) that can effectively enhance photogenerated exciton dissociation are widely used for photodetectors. The benefits of both spur investigation into how to combine these two strategies to enhance X-ray detection. Here, TiO₂ networks are incorporated into PbI₂ crystals to form interpenetrating type II heterojunctions, namely BHJs. These BHJs exhibit long-range ordering in molecular packing similar to that of single crystals. Compared with single crystals, the long-range ordered BHJs facilitate the separation of photogenerated electrons and holes to inhibit recombination, extend the mobility lifetime product by 6.4 times, and consequently improve X-ray sensitivity by 5.8 times. Hence, this work provides a new strategy using gel-grown crystals to fabricate high-performance X-ray detectors as well as a new platform for studying the behavior of X-ray-generated carriers in BHJs with long-range ordering.

Optical Probing of Crystal Lattice Configurations in Single CsPbBr3 Nanoplatelets

Quantum-confined nanostructures of CsPbBr₃ with luminescence quantum efficiencies approaching unity have shown tremendous potential for lighting and quantum light applications. In contrast to CsPbBr₃ quantum dots, where the fine structure of the emissive exciton state has been intensely discussed, the relationship among lattice orientation, shape anisotropy, and exciton fine structure in lead halide nanoplatelets has not yet been established. In this work, we investigate the fine structure of the bright triplet exciton of individual CsPbBr₃ nanoplatelets by polarization-resolved micro- and magnetophotoluminescence spectroscopy at liquid helium temperature and find a large zero-field splitting of up to 2.5 meV. A unique relation between the crystal structure and the photoluminescence emission confirms the existence of two distinct crystal configurations in such nanoplatelets with different alignments of the crystal axes with respect to the nanoplatelet facets. Polarization-resolved experiments eventually allow us to determine the absolute orientation of an individual nanoplatelet on the substrate purely by optical means.

Synthesis of Hydrated Ternary Lanthanide-Containing Chlorides Exhibiting X-ray Scintillation and Luminescence

A series of new ternary lanthanide-based chlorides, Cs₂EuCl₅(H₂O)₁₀, Cs₇LnCl₁₀(H₂O)₈ (Ln = Gd or Ho), Cs₁₀Tb₂Cl₁₇(H₂O)₁₄(H₃O), Cs₂DyCl₅(H₂O)₆, Cs₈Er₃Cl₁₇(H₂O)₂₅, and Cs₅Ln₂Cl₁₁(H₂O)₁₇ (Ln = Y, Lu, or Yb), were prepared as single crystals via a facile solution route. The compounds with compositions of Cs₇LnCl₁₀(H₂O)₈ (Ln = Gd or Ho) and Cs₅Ln₂Cl₁₁(H₂O)₁₇ (Ln = Y, Lu, or Yb) crystallize in a monoclinic crystal system in space groups C2 and P2₁/c, respectively, whereas Cs₂EuCl₅(H₂O)₁₀, Cs₁₀Tb₂Cl₁₇(H₂O)₁₄(H₃O), and Cs₈Er₃Cl₁₇(H₂O)₂₅ crystallize in orthorhombic space groups Pbcm, Pnma, and P2₁2₁2₁, respectively. Cs₂DyCl₅(H₂O)₆ crystallizes with triclinic symmetry in space group P1̅. All of these compounds exhibit complex three-dimensional structures built of isolated lanthanide polyhedral units that are linked together by extensive hydrogen bonds. Cs₂EuCl₅(H₂O)₁₀ and Cs₁₀Tb₂Cl₁₇(H₂O)₁₄(H₃O) luminesce upon irradiation with 375 nm ultraviolet light, emitting intense orange-red and green color, respectively, and Cs₁₀Tb₂Cl₁₇(H₂O)₁₄(H₃O) scintillates when exposed to X-rays. Radioluminescence (RL) measurement of Cs₁₀Tb₂Cl₁₇(H₂O)₁₄(H₃O) in powder form shows that the RL emission integrated in the range of 300-750 nm was ∼16% of BGO powder.

Quasi-Zero Dimensional Halide Perovskite Derivates: Synthesis, Status, and Opportunity

In recent decades, many technological advances have been enabled by nanoscale phenomena, giving rise to the field of nanotechnology. In particular, unique optical and electronic phenomena occur on length scales less than 10 nanometres, which enable novel applications. Halide perovskites have been the focus of intense research on their optoelectronic properties and have demonstrated impressive performance in photovoltaic devices and later in other optoelectronic technologies, such as lasers and light-emitting diodes. The most studied crystalline form is the three-dimensional one, but, recently, the exploration of the low-dimensional derivatives has enabled new sub-classes of halide perovskite materials to emerge with distinct properties. In these materials, low-dimensional metal halide structures responsible for the electronic properties are separated and partially insulated from one another by the (typically organic) cations. Confinement occurs on a crystal lattice level, enabling bulk or thin-film materials that retain a degree of low-dimensional character. In particular, quasi-zero dimensional perovskite derivatives are proving to have distinct electronic, absorption, and photoluminescence properties. They are being explored for various technologies beyond photovoltaics (e.g. thermoelectrics, lasing, photodetectors, memristors, capacitors, LEDs). This review brings together the recent literature on these zero-dimensional materials in an interdisciplinary way that can spur applications for these compounds. The synthesis methods, the electrical, optical, and chemical properties, the advances in applications, and the challenges that need to be overcome as candidates for future electronic devices have been covered.

Reproducible X-ray Imaging with a Perovskite Nanocrystal Scintillator Embedded in a Transparent Amorphous Network Structure

Metal halide perovskites are emerging scintillator materials in X-ray detection and imaging. However, the vulnerable structure of perovskites triggers unreliable performance when they are utilized in X-ray detectors under cumulative dose irradiation. Herein, a self-limited growth strategy is proposed to construct CsPbBr₃ nanocrystals that are embedded in a transparent amorphous network structure, featuring X-imaging with excellent resolution (≈16.8 lp mm^-1 ), and fast decay time (τ = 27 ns). Interestingly, it is found that the performance degradation of the scintillator, caused by the damage from high-dose X-ray irradiation, can be fully recovered after a facile thermal treatment process. This indicates a superior recycling behavior of the explored perovskites scintillator for practical applications. The recoverability of the as-explored scintillator is attributed to the low atom-migration rate in the amorphous network with high-viscosity (1 × 10¹⁴  cP). This result highlights the practical settlement of the promising perovskites for long-term, cost-effective scintillator devices.