Two-dimensional halide perovskite as β-ray scintillator for nuclear radiation monitoring

Direct detection of minimum ionizing charged particles in a perovskite single crystal detector with single particle sensitivity

We report the detection of high energy electrons of some hundreds of MeV, crossing a methylammonium lead bromide single crystal device with sensitivity down to a single electron. In the device, the released energy is close to the energy released by minimum-ionizing particles. This is the first demonstration of a perovskite-based device that can be used for tracking and counting minimum-ionizing charged particles. The device reaches single particle sensitivity with a low bias voltage of 5 V. It also shows a good linearity of the response as a function of the number of electrons in a dynamic range of approximately 104.

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.

Bright Innovations: Review of Next-Generation Advances in Scintillator Engineering

This review focuses on modern scintillators, the heart of ionizing radiation detection with applications in medical diagnostics, homeland security, research, and other areas. The conventional method to improve their characteristics, such as light output and timing properties, consists of improving in material composition and doping, etc., which are intrinsic to the material. On the contrary, we review recent advancements in cutting-edge approaches to shape scintillator characteristics via photonic and metamaterial engineering, which are extrinsic and introduce controlled inhomogeneity in the scintillator's surface or volume. The methods to be discussed include improved light out-coupling using photonic crystal (PhC) coating, dielectric architecture modification producing the Purcell effect, and meta-materials engineering based on energy sharing. These approaches help to break traditional bulk scintillators' limitations, e.g., to deal with poor light extraction efficiency from the material due to a typically large refractive index mismatch or improve timing performance compared to bulk materials. In the Outlook section, modern physical phenomena are discussed and suggested as the basis for the next generations of scintillation-based detectors and technology, followed by a brief discussion on cost-effective fabrication techniques that could be scalable.

Mn(II)-Based Metal Halide with Near-Unity Quantum Yield for White LEDs and High-Resolution X-ray Imaging

Metal halides have drawn great interest as luminescent materials and scintillators due to their outstanding optical properties. Exploring new types of phosphors with easy production processes, excellent photophysical properties, high light yields, and environmentally friendly compositions is crucial and quite challenging. Herein, a novel Mn(II)-based metal halide (4-BTP)2MnBr4 was produced using a facile solvent evaporation method, which exhibited a strong green emission peaking at 524 nm from the d-d transition of tetrahedral-coordinated Mn2+ ion and a near-unity quantum yield. The prepared white light-emitting diode device has a wide color gamut of 100.7% NTSC with CIE chromaticity coordinates of (0.32, 0.32). In addition, (4-BTP)2MnBr4 demonstrates excellent characteristics in X-ray scintillation, including a high light yield of 98 000 photons/MeV, a sensitive detection limit of 37.4 nGy/s, excellent resistance to radiation damage, and successful demonstration of X-ray imaging with high resolution at 21.3 lp/mm, revealing the potential for application in diagnostic X-ray medical imaging and industry radiation detection.

Real-time single-proton counting with transmissive perovskite nanocrystal scintillators

High-sensitivity radiation detectors for energetic particles are essential for advanced applications in particle physics, astronomy and cancer therapy. Current particle detectors use bulk crystals, and thin-film organic scintillators have low light yields and limited radiation tolerance. Here we present transmissive thin scintillators made from CsPbBr3 nanocrystals, designed for real-time single-proton counting. These perovskite scintillators exhibit exceptional sensitivity, with a high light yield (~100,000 photons per MeV) when subjected to proton beams. This enhanced sensitivity is attributed to radiative emission from biexcitons generated through proton-induced upconversion and impact ionization. These scintillators can detect as few as seven protons per second, a sensitivity level far below the rates encountered in clinical settings. The combination of rapid response (~336 ps) and pronounced ionostability enables diverse applications, including single-proton tracing, patterned irradiation and super-resolution proton imaging. These advancements have the potential to improve proton dosimetry in proton therapy and radiography.

Arising 2D Perovskites for Ionizing Radiation Detection

2D perovskites have greatly improved moisture stability owing to the large organic cations embedded in the inorganic octahedral structure, which also suppresses the ions migration and reduces the dark current. The suppression of ions migration by 2D perovskites effectively suppresses excessive device noise and baseline drift and shows excellent potential in the direct X-ray detection field. In addition, 2D perovskites have gradually emerged with many unique properties, such as anisotropy, tunable bandgap, high photoluminescence quantum yield, and wide range exciton binding energy, which continuously promote the development of 2D perovskites in ionizing radiation detection. This review aims to systematically summarize the advances and progress of 2D halide perovskite semiconductor and scintillator ionizing radiation detectors, including reported alpha (α) particle, beta (β) particle, neutron, X-ray, and gamma (γ) ray detection. The unique structural features of 2D perovskites and their advantages in X-ray detection are discussed. Development directions are also proposed to overcome the limitations of 2D halide perovskite radiation detectors.

High-Performance Hard X-Ray Imaging Detector Using Facet-Dependent Bismuth Vanadate

Bismuth vanadate (BiVO4) exhibits large absorption efficiency for hard X-rays, which endows it with a robust capacity to attenuate X-ray radiation across a broad energy range. The anisotropic properties of BiVO4 allow for the manipulation of their physical and chemical characteristics through crystallographic orientation and exposed facets. In this study, the issue of heavy recombination caused by sluggish electron transport in BiVO4 is successfully addressed by enhancing the abundance of the (040) crystal face ratio using a Co2+ crystal face exposure agent. The facet-dependent modifications exhibit excellent and balanced intrinsic charge transport properties, and finely optimize both the sensitivity and detection limit of BiVO4 X-ray detectors. As a result, ultra-stable BiVO4 metal oxide X-ray detectors demonstrate a high sensitivity of 3164 µC Gyair -1 cm-2 and a low detection limit of 20.76 nGyair s-1 under 110 kVp hard X-rays, establishing a new benchmark for X-ray detectors based on polycrystalline Bi-halides and metal oxides. These findings highlight the significance of crystal orientation in optimizing materials for X-ray detection, setting a new sensitivity record for X-ray detectors based on polycrystalline Bi-halides and metal oxides, which paves the way for the development of advanced, low-dose, and highly stable imaging systems specifically for hard X-rays.

Enhanced Storage Capacity via Anion Substitution for Advanced Delayed X-ray Detection

X-ray radiation information storage, characterized by its ability to detect radiation with delayed readings, shows great promise in enabling reliable and readily accessible X-ray imaging and dosimetry in situations where conventional detectors may not be feasible. However, the lack of specific strategies to enhance the memory capability dramatically hampers its further development. Here, we present an effective anion substitution strategy to enhance the storage capability of NaLuF4:Tb3+ nanocrystals attributed to the increased concentration of trapping centers under X-ray irradiation. The stored radiation information can be read out as optical brightness via thermal, 980 nm laser, or mechanical stimulation, avoiding real-time measurement under ionizing radiation. Moreover, the radiation information can be maintained for more than 13 days, and the imaging resolution reaches 14.3 lp mm-1. These results demonstrate that anion substitution methods can effectively achieve high storage capability and broaden the application scope of X-ray information storage.

Two-Dimensional Hybrid Perovskite with High-Sensitivity Optical Thermometry Sensors

Optical thermometry has gained significant attention due to its remarkable sensitivity and noninvasive, rapid response to temperature changes. However, achieving both high absolute and relative temperature sensitivity in two-dimensional perovskites presents a substantial challenge. Here, we propose a novel approach to address this issue by designing and synthesizing a new narrow-band blue light-emitting two-dimensional perovskite named (C8H12NO2)2PbBr4 using a straightforward solution-based method. Under excitation of near-ultraviolet light, (C8H12NO2)2PbBr4 shows an ultranarrow emission band with the full width at half-maximum (FWHM) of only 19 nm. Furthermore, its luminescence property can be efficiently tuned by incorporating energy transfer from host excitons to Mn2+. This energy transfer leads to dual emission, encompassing both blue and orange emissions, with an impressive energy transfer efficiency of 38.3%. Additionally, we investigated the temperature-dependent fluorescence intensity ratio between blue emission of (C8H12NO2)2PbBr4 and orange emission of Mn2+. Remarkably, (C8H12NO2)2PbBr4:Mn2+ exhibited maximum absolute sensitivity and relative sensitivity values of 0.055 K-1 and 3.207% K-1, respectively, within the temperature range of 80-360 K. This work highlights the potential of (C8H12NO2)2PbBr4:Mn2+ as a promising candidate for optical thermometry sensor application. Moreover, our findings provide valuable insights into the design of narrow-band blue light-emitting perovskites, enabling the achievement of single-component dual emission in optical thermometry sensors.

Scintillation Properties of CsPbBr3 Nanocrystals Prepared by Ligand-Assisted Reprecipitation and Dual Effect of Polyacrylate Encapsulation toward Scalable Ultrafast Radiation Detectors

Lead halide perovskite nanocrystals (LHP-NCs) embedded in polymeric hosts are gaining attention as scalable and low-cost scintillation detectors for technologically relevant applications. Despite rapid progress, little is currently known about the scintillation properties and stability of LHP-NCs prepared by the ligand assisted reprecipitation (LARP) method, which allows mass scalability at room temperature unmatched by any other type of nanostructure, and the implications of incorporating LHP-NCs into polyacrylate hosts are still largely debated. Here, we show that LARP-synthesized CsPbBr3 NCs are comparable to particles from hot-injection routes and unravel the dual effect of polyacrylate incorporation, where the partial degradation of LHP-NCs luminescence is counterbalanced by the passivation of electron-poor defects by the host acrylic groups. Experiments on NCs with tailored surface defects show that the balance between such antithetical effects of polymer embedding is determined by the surface defect density of the NCs and provide guidelines for further material optimization.

High-Confidentiality X-Ray Imaging Encryption Using Prolonged Imperceptible Radioluminescence Memory Scintillators

X-ray imaging plays an increasingly crucial role in clinical radiography, industrial inspection, and military applications. However, current X-ray imaging technologies have difficulty in protecting against information leakage caused by brute force attacks via trial-and-error. Here high-confidentiality X-ray imaging encryption by fabricating ultralong radioluminescence memory films composed of lanthanide-activated nanoscintillators (NaLuF4 : Gd3+ or Ce3+ ) with imperceptible purely-ultraviolet (UV) emission is reported. Mechanistic investigations unveil that ultralong X-ray memory is attributed to the long-lived trapping of thermalized charge carriers within Frenkel defect states and subsequent slow release in the form of imperceptible radioluminescence. The encrypted X-ray imaging can be securely stored in the memory film for more than 7 days and optically decoded by perovskite nanocrystal. Importantly, this encryption strategy can protect X-ray imaging information against brute force trial-and-error attacks through the perception of lifetime change in the persistent radioluminescence. It is further demonstrated that the as-fabricated flexible memory film enables achieving of 3D X-ray imaging encryption of curved objects with a high spatial resolution of 20 lp/mm and excellent recyclability. This study provides valuable insights into the fundamental understanding of X-ray-to-UV conversion in nanocrystal lattices and opens up a new avenue toward the development of high-confidential 3D X-ray imaging encryption technologies.

Manipulation of Shallow-Trap States in Halide Double Perovskite Enables Real-Time Radiation Dosimetry

Storage phosphors displaying defect emissions are indispensable in technologically advanced radiation dosimeters. The current dosimeter is limited to the passive detection mode, where ionizing radiation-induced deep-trap defects must be activated by external stimulation such as light or heat. Herein, we designed a new type of shallow-trap storage phosphor by controlling the dopant amounts of Ag+ and Bi3+ in the host lattice of Cs2NaInCl6. A distinct phenomenon of X-ray-induced emission (XIE) is observed for the first time in an intrinsically nonemissive perovskite. The intensity of XIE exhibits a quantitative relationship with the accumulated dose, enabling a real-time radiation dosimeter. Thermoluminescence and in situ X-ray photoelectron spectroscopy verify that the emission originates from the radiative recombination of electrons and holes associated with X-ray-induced traps. Theoretical calculations reveal the evolution process of Cl-Cl dimers serving as hole trap states. Analysis of temperature-dependent radioluminescence spectra provides evidence that the intrinsic electron-phonon interaction in 0.005 Ag+@ Cs2NaInCl6 is significantly reduced under X-ray irradiation. Moreover, 0.025 Bi3+@ Cs2NaInCl6 shows an elevated sensitivity to the accumulated dose with a broad response range from 0.08 to 45.05 Gy. This work discloses defect manipulation in halide double perovskites, giving rise to distinct shallow-trap storage phosphors that bridge traditional deep-trap storage phosphors and scintillators and enabling a brand-new type of material for real-time radiation dosimetry.

Low-Temperature Emission Dynamics of Methylammonium Lead Bromide Hybrid Perovskite Thin Films at the Sub-Micrometer Scale

We study the low-temperature (T = 4.7 K) emission dynamics of a thin film of methylammonium lead bromide (MAPbBr3), prepared via the anti-solvent method. Using intensity-dependent (over 5 decades) hyperspectral microscopy under quasi-resonant (532 nm) continuous wave excitation, we revealed spatial inhomogeneities in the thin film emission. This was drastically different at the band-edge (∼550 nm, sharp peaks) than in the emission tail (∼568 nm, continuum of emission). We are able to observe regions of the film at the micrometer scale where emission is dominated by excitons, in between regions of trap emission. Varying the density of absorbed photons by the MAPbBr3 thin films, two-color fluorescence lifetime imaging microscopy unraveled the emission dynamics: a fast, resolution-limited (∼200 ps) monoexponential tangled with a stretched exponential decay. We associate the first to the relaxation of excitons and the latter to trap emission dynamics. The obtained stretching exponents can be interpreted as the result of a two-dimensional electron diffusion process: Förster resonant transfer mechanism. Furthermore, the non-vanishing fast monoexponential component even in the tail of the MAPbBr3 emission indicates the subsistence of localized excitons. Finally, we estimate the density of traps in MAPbBr3 thin films prepared using the anti-solvent method at n∼1017 cm-3.

Moisture-Tailored 2D Dion-Jacobson Perovskites for Reconfigurable Optoelectronics

Humidity- and moisture-induced degradation has been a longstanding problem in perovskite materials, affecting their long-term stability during applications. Counterintuitively, the moisture is leveraged to tailor the reversible hydrochromic behaviors of a new series of 2D Dion-Jacobson (DJ) perovskites for reconfigurable optoelectronics. In particular, the hydrogen bonds between organic cations and water molecules can be dynamically modulated via moisture removal/exposure. Remarkably, such modulation confines the movement of the organic cations close to the original position, preventing their escape from crystal lattices. Furthermore, this mechanism is elucidated by theoretical analysis using first-principles calculations and confirmed with the experimental characterizations. The reversible fluorescent transition 2D DJ perovskites show excellent cyclical properties, presenting untapped opportunities for reconfigurable optoelectronic applications. As a proof-of-concept demonstration, an anti-counterfeiting display is shown based on patterned reversible 2D DJ perovskites. The results represent a new avenue of reconfigurable optoelectronic application with 2D DJ perovskites for humidity detection, anti-counterfeiting, sensing, and other emerging photoelectric intelligent technologies.

Controlling Phase Transitions in Two-Dimensional Perovskites through Organic Cation Alloying

We demonstrate control over the phase transition temperature of Ruddlesden-Popper two-dimensional (2D) perovskites by alloying alkyl organic cations of varying lengths. By blending hexylammonium with pentylammonium or heptylammonium cations in different ratios, we continuously tune the phase transition temperature of 2D perovskites from approximately 40 to -80 °C in both crystalline powders and thin films. Correlating temperature-dependent grazing incidence wide-angle X-ray scattering and photoluminescence spectroscopy, we also demonstrate that the phase transition in the organic layer couples to the inorganic lattice, impacting PL intensity and wavelength. We take advantage of changes in PL intensity to image the dynamics of this phase transition and show asymmetric phase growth at the microscale. Our findings provide the necessary design principles to precisely control phase transitions in 2D perovskites for applications such as solid-solid phase change materials and barocaloric cooling.

Sub-Nanosecond 2D Perovskite Scintillators by Dielectric Engineering

Perovskite materials have demonstrated great potential for ultrafast scintillators with high light yield. However, the decay time of perovskite still cannot be further minimized into sub-nanosecond region, while sub-nanosecond scintillators are highly demanded in various radiation detection, including high speed X-ray imaging, time-of-flight based tomography or particle discrimination, and timing resolution measurement in synchrotron radiation facilities, etc. Here, a rational design strategy is showed to shorten the scintillation decay time, by maximizing the dielectric difference between organic amines and Pb-Br octahedral emitters in 2D organic-inorganic hybrid perovskites (OIHP). Benzimidazole (BM) with low dielectric constant inserted between [PbBr₆ ]^2- layers, resulting in a surprisingly large exciton binding energy (360.3 ± 4.8 meV) of 2D OIHP BM₂ PbBr₄ . The emitting decay time is shortened as 0.97 ns, which is smallest among all the perovskite materials. Moreover, the light yield is 3190 photons MeV^-1 , which is greatly higher than conventional ultrafast scintillator BaF₂ (1500 photons MeV^-1 ). The rare combination of ultrafast decay time and considerable light yield renders BM₂ PbBr₄ excellent performance in γ-ray, neutron, α-particle detection, and the best theoretical coincidence time resolution of 65.1 ps, which is only half of the reference sample LYSO (141.3 ps).

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.

Achieving High Responsivity and Detectivity in a Quantum-Dot-in-Perovskite Photodetector

This work reports on quantum dots (QDs) in perovskite photodetectors showing high optoelectronic performance via quantum-dot-assisted charge transmission. The self-powered broad-band photodetector constructed with SnS QDs in FAPb_0.5Sn_0.5I₃ perovskite can capture incoming optical signals directly at zero bias. The QDs-in-perovskite photodetector exhibits a high sensitivity in the wavelength range from 300 to 1000 nm. Its responsivity at 850 nm reaches 521.7 mA W^-1, and a high specific detectivity of 2.57 × 10¹² jones can be achieved, which is well beyond the level of previous self-powered broad-band photodetectors. The capability of quantum-dot-in-perovskite photodetectors as data receivers has been further demonstrated in a visible-light communication application.

Factors influencing self-trapped exciton emission of low-dimensional metal halides

In this review, we mainly summarized the structure distortion, molecular engineering, electron–phonon coupling effect, external temperature and pressure, and metal ion doping that influence the self-trapped exciton emission of low-dimensional metal halides (LDMHs).

Multispectral Large-Panel X-ray Imaging Enabled by Stacked Metal Halide Scintillators

Conventional energy-integration black-white X-ray imaging lacks the spectral information of X-ray photons. Although X-ray spectra (energy) can be distinguished by the photon-counting technique typically with CdZnTe detectors, it is very challenging to be applied to large-area flat-panel X-ray imaging (FPXI). Herein, multilayer stacked scintillators of different X-ray absorption capabilities and scintillation spectra are designed; in this scenario, the X-ray energy can be discriminated by detecting the emission spectra of each scintillator; therefore, multispectral X-ray imaging can be easily obtained by color or multispectral visible-light camera in a single shot of X-rays. To verify this idea, stacked multilayer scintillators based on several emerging metal halides are fabricated in a cost-effective and scalable solution process, and proof-of-concept multispectral (or multi-energy) FPXI are experimentally demonstrated. The dual-energy X-ray image of a "bone-muscle" model clearly shows the details that are invisible in conventional energy-integration FPXI. By stacking four layers of specifically designed multilayer scintillators with appropriate thicknesses, a prototype FPXI with four energy channels is realized, proving its extendibility to multispectral or even hyperspectral X-ray imaging. This study provides a facile and effective strategy to realize multispectral large-area flat-panel X-ray imaging.

γ-ray Radiation Hardness of CsPbBr3 Single Crystals and Single-Carrier Devices

The superior environmental stability of all-inorganic metal halide perovskites compared to their organic-inorganic counterparts makes them more promising in practical applications. Here, the stability of an archetypical all-inorganic CsPbBr₃ single crystal and its single-carrier devices under ⁶⁰Co γ-ray irradiation was investigated. The CsPbBr₃ single crystal itself shows ostensible hardness as its structural and optical properties present imperceptible changes even with a total ionizing dose of 800 krad. Unexpectedly, the single crystal-based single-carrier devices exhibit apparent dose-dependent hardness. The performance of the hole-only device suffers from more deterioration than the electron-only device under high irradiation doses (>400 krad). Our results reveal that such a discrepancy originates from the different influences of γ-ray irradiation-induced defects on the transport behaviors of holes and electrons in CsPbBr₃ single-crystal devices. These findings offer a new understanding of the interaction mechanism between γ-photons and all-inorganic metal halide perovskite-based devices.

Extreme-Ultraviolet Excited Scintillation of Methylammonium Lead Bromide Perovskites

Inorganic-Organic lead halide materials have been recognized as potential high-energy X-ray detectors because of their high quantum efficiencies and radiation hardness. Surprisingly little is known about whether the same is true for extreme-ultraviolet (XUV) radiation, despite applications in nuclear fusion research and astrophysics. We used a table-top high-harmonic generation setup in the XUV range between 20 and 45 eV to photoexcite methylammonium lead bromide (MAPbBr₃) and measure its scintillation properties. The strong absorbance combined with multiple carriers being excited per photon yield a very high carrier density at the surface, triggering photobleaching reactions that rapidly reduce the emission intensity. Concurrent to and in spite of this photobleaching, a recovery of the emission intensity as a function of dose was observed. X-ray photoelectron spectroscopy and X-ray diffraction measurements of XUV-exposed and unexposed areas show that this recovery is caused by XUV-induced oxidation of MAPbBr₃, which removes trap states that normally quench emission, thus counteracting the rapid photobleaching caused by the extremely high carrier densities. Furthermore, it was found that preoxidizing the sample with ozone was able to prolong and improve this intensity recovery, highlighting the impact of surface passivation on the scintillation properties of perovskite materials in the XUV range.

Highly Stable and Moisture-Immune Monocomponent White Perovskite Phosphor by Trifluoromethyl (-CF3) Regulation

Halide perovskites are emerging as promising candidates for white light solid state lighting. Nevertheless, there are still challenges of a high water stability, a tunable color temperature, and a high photoluminescence quantum yield (PLQY). Herein, we report hydrophobic, electron-withdrawing trifluoromethyl (-CF₃)-modified phenethylamine lead bromide (PEA₂PbBr₄) with ultrahigh stability in water for >2 months, and the broadband white light emission is illustrated by self-trapped excitons attributed to exciton-phonon coupling that coordinate molecular vibration, lattice distortion, and electrostatic interaction. In particular, by Mn²⁺ doping, the emission color can be tuned from cold (10237 K) to warm (2406 K), and a greatly enhanced PLQY of ≤87.93% can be achieved. Furthermore, the perovskites also possess an excellent color rendering index (the highest is 94). A monocomponent white light-emitting diode with amazing CIE 1931 coordinates of (0.33, 0.32) is further assembled, demonstrating a luminance of 471.5 cd m^-2 at 50 mA and good long-term operation stability after >2 months. This study of highly efficient and stable perovskites with high-quality white light emission will open up new opportunities in solid state lighting.

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 .

Halide perovskites and perovskite related materials for particle radiation detection

Radiation detectors are widely used in physics, materials science, chemistry, and biology. Halide perovskites are known for their superior properties including tunable bandgaps and chemical compositions, high defect tolerance, solution-processable synthesis of films and crystals, and high carrier diffusion length. Recently, halide perovskites have attracted enormous interest as particle radiation detectors for both charged (α and β) and uncharged (neutrons) particles. Solid-state detectors based on single crystal perovskites can detect α particles and thermal neutrons with energy-resolved spectra. Halide perovskite scintillators are also able to detect β particles and fast neutrons. In this review, we briefly introduce the fundamentals of radiation detection and summarize the recent progress on halide perovskite detectors for particle radiation.

Two-Dimensional Dion-Jacobson Perovskite (NH3C4H8NH3)CsPb2Br7 with High X-ray Sensitivity and Peak Discrimination of α-Particles

Two-dimensional (2D) halide perovskites have attracted extensive interest because of their excellent optoelectronic properties, structural diversity, and promising stability. Herein, we grow a novel 2D Dion-Jacobson halide perovskite, (BDA)CsPb₂Br₇ (BDA = 1,4-butanediamine, NH₃C₄H₈NH₃²⁺), which exhibits a large bandgap (∼2.76 eV), high resistivity (∼4.35 × 10¹⁰ Ω·cm), and considerable switching ratio (>700), indicating great potential for radiation detection. Both experimental and calculated results demonstrate that (BDA)CsPb₂Br₇ has a significantly improved mobility compared to those of Ruddlesden-Popper perovskites (BA)₂CsPb₂Br₇ and (i-BA)₂CsPb₂Br₇, which is attributed to the shorter interlayer distance leading to the enhanced orbital interactions. The resulting (BDA)CsPb₂Br₇ detector along the out-of-plane direction achieves a high X-ray sensitivity of 725.5 μC·Gy^-1·cm^-2. Another fascinating attribute is that the detector exhibits good peak discrimination with an energy resolution of ∼37% when illuminated by the ²⁴¹Am@5.48 MeV α-particles under a negative bias of 260 V. These results provide a broad prospect for 2D Dion-Jacobson perovskites for future radiation detection applications.

Further Advancement of Perovskite Single Crystals

Halide perovskite (HP) single crystals (SCs) are garnering extensive attention as active materials to substitute polycrystalline counterparts in solar cells, photodiodes, and photodetectors, etc. Nevertheless, the large thickness and defect-rich surface results in severe carrier recombination and becomes the major bottleneck for augmented performance. In this perspective, we are looking forward to explaining in detail why the SCs hardly unleash their engrossing potential and introduce two parallel paths for further advancement. First is the modification of thick SCs by reducing the prepared thickness or surface passivation. Second is the large thickness that is conducive to the sufficient absorption of high-energy rays with strong penetrating ability and is beneficial to the thermoelectric effect due to the ultralow thermal conductivity of HPs. These applications provide a roundabout strategy to exploit freestanding SCs with a large thickness. Herein, direct modification and application of thick SCs are systematically introduced, expecting to give rise to the prosperity of HP SCs.

Nucleation Engineering in Sprayed MA3Bi2I9 Films for Direct-Conversion X-ray Detectors

Metal halide perovskite and its derivatives show great promise in X-ray detection. However, large-scale fabrication of high-quality thick perovskite films is still full of challenges due to the complicated crystal nucleation process that always introduces lots of cracks or pinholes in the final perovskite film. Here, a MA₃Bi₂I₉ film was fabricated by the cost-effective, scalable spraying process, and MACl was used as an additive to effectively tune the crystallization process. As a result, a dense MA₃Bi₂I₉ film constituted by large grains was obtained, which has a high carrier mobility of ∼1 cm² V^-1 s^-1 and a large activation energy (E_a) for ion migration of 0.91 eV. Thanks to the outstanding optoelectronic characteristics, X-ray detectors with a configuration of ITO/MA₃Bi₂I₉/Au show a sensitivity of 35 μC Gy_air^-1 cm^-2 and a limit of detection (LoD) of 0.14 μGy_airs^-1, which is outstanding compared with commercial α-Se detectors.

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.

Hydrogen-Rich 2D Halide Perovskite Scintillators for Fast Neutron Radiography

A fast neutron has strong penetration ability through dense and bulky objects, which makes it an ideal nondestructive technology for detecting voids, cracks, or other defects inside large equipment. However, the lack of effective fast neutron detection materials limits its application. Perovskites have shown excellent optical properties in many areas, but they are absent from fast neutron detection imaging because they cannot directly absorb fast neutrons and emit luminescence. Here, we demonstrate a hydrogen-rich long-chain organic amine modified two-dimensional (2D) perovskite fast neutron scintillator, Mn-(C₁₈H₃₇NH₃)₂PbBr₄(Mn-STA₂PbBr₄). Its hydrogen density can reach 9.51 × 10²⁸ m^-3, and the photoluminescence quantum yield can reach 58.58%, so it is possible to integrate fast neutron absorption and luminescence into a single compound. More importantly, Mn-STA₂PbBr₄ can be made into a large-area self-supporting fast neutron scintillator plate with satisfactory spatial resolution (0.5 lp/mm (lp: line pairs)). This strategy provides a simple and promising choice for fast neutron scintillator nondestructive testing.

Water-Molecule-Induced Emission Transformation of Zero-Dimension Antimony-Based Metal Halide

Low-dimensional organic-inorganic metal halides have recently emerged as a class of promising luminescent materials. However, the intrinsic toxicity of lead would strongly hamper future application. Herein, we synthesized a new type of lead-free zero-dimensional (0D) antimony-based organic-inorganic metal halide single crystals, (PPZ)₂SbCl₇·5H₂O (PPZ = 1-phenylpiperazine), which features a broadband emission at 720 nm. Ultrafast transient absorption and temperature-dependent photoluminescence (PL) spectra are combined to investigate the PL mechanism, revealing that self-trapped exciton recombination was involved. Furthermore, it is interesting that (PPZ)₂SbCl₇·5H₂O material shows reversible PL emission transformation between red light (720 nm) and yellow light (590 nm) as water molecules are inserted or removed from the lattice. Such reversible emission transformation phenomenon renders the (PPZ)₂SbCl₇·5H₂O as a potential low-cost water sensing material.

Isotypic lanthanide-organic frameworks and scintillating films with colour-tunable X-ray radioluminescence for imaging applications

Lanthanide-organic frameworks (LnOFs) have been brought into focus due to their unique structure-function relevance, and have shown good application prospects in many fields. According to the characteristics of scintillating materials, we synthesized two isomorphic LnOFs with the lanthanides terbium and europium as emission centers: Tb(bmb)₃·H₂O (LnOF-1) and Eu(bmb)₃·H₂O (LnOF-2). Tb³⁺ and Eu³⁺ were used as X-ray absorption centers, and large conjugated organic ligands were used as energy transfer bridges, which can effectively convert X-rays into visible light. LnOF-1 and LnOF-2 show good X-ray scintillation performance and anti-radiation stability. At the same time, we prepared a LnOF-1 mixed matrix scintillating film by the physical deposition method for X-ray imaging experiments, and its spatial resolution can reach 9.5 lp mm^-1@MTF20%. The excellent imaging application effect prospect makes the lanthanide-organic frameworks show development potential in the field of scintillating materials.

Realizing Near-Unity Quantum Efficiency of Zero-Dimensional Antimony Halides through Metal Halide Structural Modulation

Zero-dimensional (0D) organic metal halides have attracted significant attention because of their exceptional structure tunability and excellent optical characteristics. However, controllable synthesis of a desirable configuration of metal halide species in a rational way remains a formidable challenge, and how the unique crystal structures affect the photophysical properties are not yet well understood. Here, a reasonable metal halide structural modulation strategy is proposed to realize near-unity photoluminescence quantum efficiency (PLQE) in 0D organic antimony halides. By carefully controlling the reaction conditions, both 0D (C₁₂H₂₈N)₂SbCl₅ and (C₁₂H₂₈N)SbCl₄ with different metal halide configurations can be prepared. (C₁₂H₂₈N)₂SbCl₅ with pyramid-shaped [SbCl₅]^2- species exhibits yellow emission with a near-unity PLQE of 96.8%, while (C₁₂H₂₈N)SbCl₄ with seesaw-shaped [SbCl₄]^- species is not emissive at room temperature. Theoretical calculations indicate that the different photophysical properties of these two crystals can be attributed to the different symmetries of their crystal structures. (C₁₂H₂₈N)₂SbCl₅ adopts a triclinic structure with P-1 symmetry, while (C₁₂H₂₈N)SbCl₄ possesses a monoclinic structure with P2₁/c symmetry, which has an inversion center, and thus the optical transitions between their band-edge states give a minimal dipole intensity because of their similar parity character. In addition, we also successfully synthesized (C₁₂H₂₈N)₂SbCl₅ nanocrystals for the first time, which are particularly appealing for their solution processibility and excellent optical properties. Furthermore, (C₁₂H₂₈N)₂SbCl₅ nanocrystals flexible composite film shows bright yellow emission under β-ray excitation, suggesting a strong potential of (C₁₂H₂₈N)₂SbCl₅ for β-ray detection.

Recent Advances in Synthesis, Properties, and Applications of Metal Halide Perovskite Nanocrystals/Polymer Nanocomposites

Metal halide perovskite nanocrystals (PNCs) have recently garnered tremendous research interest due to their unique optoelectronic properties and promising applications in photovoltaics and optoelectronics. Metal halide PNCs can be combined with polymers to create nanocomposites that carry an array of advantageous characteristics. The polymer matrix can bestow stability, stretchability, and solution-processability while the PNCs maintain their size-, shape- and composition-dependent optoelectronic properties. As such, these nanocomposites possess great promise for next-generation displays, lighting, sensing, biomedical technologies, and energy conversion. The recent advances in metal halide PNC/polymer nanocomposites are summarized here. First, a variety of synthetic strategies for crafting PNC/polymer nanocomposites are discussed. Second, their array of intriguing properties is examined. Third, the broad range of applications of PNC/polymer nanocomposites is highlighted, including light-emitting diodes (LEDs), lasers, and scintillators. Finally, an outlook on future research directions and challenges in this rapidly evolving field are presented.

2D perovskite-based high spatial resolution X-ray detectors

X-ray radiography is the most widely used imaging technique with applications encompassing medical and industrial imaging, homeland security, and materials research. Although a significant amount of research and development has gone into improving the spatial resolution of the current state-of-the-art indirect X-ray detectors, it is still limited by the detector thickness and microcolumnar structure quality. This paper demonstrates high spatial resolution X-ray imaging with solution-processable two-dimensional hybrid perovskite single-crystal scintillators grown inside microcapillary channels as small as 20 µm. These highly scalable non-hygroscopic detectors demonstrate excellent spatial resolution similar to the direct X-ray detectors. X-ray imaging results of a camera constructed using this scintillator show Modulation Transfer Function values significantly better than the current state-of-the-art X-ray detectors. These structured detectors open up a new era of low-cost large-area ultrahigh spatial resolution high frame rate X-ray imaging with numerous applications.

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.

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.

Hybrid halide perovskite neutron detectors

Interest in fast and easy detection of high-energy radiation (x-, γ-rays and neutrons) is closely related to numerous practical applications ranging from biomedicine and industry to homeland security issues. In this regard, crystals of hybrid halide perovskite have proven to be excellent detectors of x- and γ-rays, offering exceptionally high sensitivities in parallel to the ease of design and handling. Here, we demonstrate that by assembling a methylammonium lead tri-bromide perovskite single crystal (CH₃NH₃PbBr₃ SC) with a Gadolinium (Gd) foil, one can very efficiently detect a flux of thermal neutrons. The neutrons absorbed by the Gd foil turn into γ-rays, which photo-generate charge carriers in the CH₃NH₃PbBr₃ SC. The induced photo-carriers contribute to the electric current, which can easily be measured, providing information on the radiation intensity of thermal neutrons. The dependence on the beam size, bias voltage and the converting distance is investigated. To ensure stable and efficient charge extraction, the perovskite SCs were equipped with carbon electrodes. Furthermore, other types of conversion layers were also tested, including borated polyethylene sheets as well as Gd grains and Gd₂O₃ pellets directly engulfed into the SCs. Monte Carlo N-Particle (MCNP) radiation transport code calculations quantitatively confirmed the detection mechanism herein proposed.

Thermal and photo stability of all inorganic lead halide perovskite nanocrystals

Inorganic lead halide perovskite (ILHP) nanocrystals (NCs) show great potential in solid state lighting and next generation display technology due to their excellent optical properties. However, almost all ILHP NCs are still facing the problem of unstable luminescence properties caused by heating and/or UV illumination. Further improving the thermal and photo stability of ILHP NCs has become the most urgent challenge for their practical application. This Perspective review specifically focuses on the thermal and photo stability of ILHP NCs, discusses and analyzes the factors that affect the thermal and photo stability of ILHP NCs from the perspective of surface ligands and structure composition, summarizes the current strategies to improve the thermal and photo stability of ILHP NCs, and presents the key challenges and perspectives on the research for the improvement of thermal and photo stability of ILHP NCs.

Perovskite Solar Cells for Space Applications: Progress and Challenges

Metal halide perovskites have aroused burgeoning interest in the field of photovoltaics owing to their versatile optoelectronic properties. The outstanding power conversion efficiency, high specific power (i.e., power to weight ratio), compatibility with flexible substrates, and excellent radiation resistance of perovskite solar cells (PSCs) enable them to be a promising candidate for next-generation space photovoltaic technology. Nevertheless, compared with other practical space photovoltaics, such as silicon and III-V multi-junction compound solar cells, the research on PSCs for space applications is just in the infancy stage. Therefore, there are considerable interests in further strengthening relevant research from the perspective of both mechanism and technology. Consequently, the approaches used for and the consequences of PSCs for space applications are reviewed. This review provides an overview of recent progress in PSCs for space applications in terms of performance evolution and mechanism exploration of perovskite films and devices under space extreme environments.