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Significant progress is achieved in the development of hybrid lead halide perovskite‐based X‐ray detectors. An in‐depth understanding of the impact of X‐ray irradiation on charge carrier behaviors is essential to assess the long‐term operational reliability of these devices. In this study, high‐quality methylammonium lead bromide (MAPbBr3) single crystals with good environmental stability are grown by an inverse temperature method, and the evolution of their carrier transport capacity is investigated by tracking the optoelectronic properties of MAPbBr3 single crystal devices under X‐ray irradiation with different fluence. Notably, the carrier transport capacity is enhanced when the X‐ray fluence is between 1.2 × 1017 and 1.8 × 1017 photons, as evidenced by improved optoelectronic properties and reduced trap state density. Conversely, a larger X‐ray fluence of 3.6 × 1017 photons causes unrepaired decomposition of the MAPbBr3 single crystals and severe degradation of their carrier transport capacity. These findings provide valuable insights for the application of hybrid lead perovskite single crystals in X‐ray detection, emphasizing the importance of optimizing X‐ray fluence levels for sustained device performance. [ABSTRACT FROM AUTHOR]

The recently reported two-dimensional lead halide perovskites have attracted much attention in high-energy radiation detector applications due to its high structural stability and low ion migration. However, the increased exciton binding energy and the charge transport barrier resulting from the A-site cation can easily limit the charge extraction and device performance. As an emerging material in high-energy detection field, guanidinium {GA+ = [C(NH2)3]+} is a relatively large organic cation composed of three amino groups, which can enhance the hydrogen bond formation and the van der Waals interactions with the metal halide framework. Meanwhile, the polymer symmetry of GA+ cation leads to almost zero dipole moments, excellent electronic properties, and high thermodynamic stability. However, there is a lack of report on the preparation, structure, and properties of GA-based 2D perovskite single crystals as well as their applications in x-ray detection. Herein, we have synthesized large-size two-dimensional GA2PbI4 single crystals with a bandgap of 2.28 eV by cooling crystallization and applied them to x-ray detectors. GA2PbI4 single crystals exhibit a high μτ product of 7.5 × 10−4 cm2 V−1 and a low trap density of 6.44 × 108 cm−3. An effective x-ray photoresponse was realized with a sensitivity as high as 392.4 μC Gyair−1 cm−2. The unique structure and excellent charge transport properties of GA+ organic cations exhibit promising prospects in high-performance x-ray detection. [ABSTRACT FROM AUTHOR]

Cs3Bi2I9 (CBI) is a promising material for direct X‐ray detectors. However, for the solution method, due to the difference in the chemical potential of Cs+, Bi3+, I− ions in the solvent, the composition of CBI single crystals (SCs) prepared by the solution method often deviates from the stoichiometric ratio, resulting in the formation of many defects in the material, which degrades the quality of the SC. Herein, Br− and Cl− are used as dopants to produce CBI SCs by the top seed solution method. It can be speculated that the dopant ions can reduce the VI defects in the CBI by means of density functional theory calculations. The carrier lifetimes of CBI SCs doped with Br− and Cl− have been increased to 41.7 and 13.0 ns, respectively. Meanwhile, the defect densities of the SCs are reduced to 1.02 × 109 and 1.85 × 109 cm−3, respectively. X‐ray detectors based on Br‐doped CBI and Cl‐doped CBI SCs exhibit high X‐ray sensitivity of 23071.3 and 18525.3 μC Gyair−1 cm−2 at an electric field of 40 V mm−1, respectively. In addition, the X‐ray detection limit reaches 1.07 and 1.35 nGyairs−1 at an electric field of 2.5 V mm−1, respectively. [ABSTRACT FROM AUTHOR]

Owing to the large x-ray attenuation coefficient, appropriate bandgap, high resistivity, and high mobility-lifetime (μτ) product, binary II–VI semiconductor CdSe is a promising x-ray detection material and it has exhibited excellent x-ray detection at room temperature (RT). For further improving the characteristics of CdSe x-ray detectors, the electrical properties of CdSe single crystals (SCs) grown through the pressure-assisted vertical Bridgman method and their x-ray detection performance have been investigated at RT and liquid nitrogen temperature (LNT), respectively. The significantly enhanced x-ray photocurrent and the prolonged response time of the devices operating at LNT indicate the photogenerated carrier lifetime could be increased by the enhanced trapping–detrapping effect obviously, and the μτ product of CdSe SCs increases from 1.39 × 10−5 to 5.34 × 10−4 cm2 V−1 with temperature lowering from RT to LNT. Meanwhile, an ultrahigh sensitivity of 5.24 × 106μC Gyair−1 cm−2 and an extremely low detection limit of 3.68 nGyair s−1 have been acquired by the CdSe SC based x-ray detectors at LNT, which is 140 times higher and 5.8 times lower than it has been at RT. Compared with conventional semiconductor x-ray detectors, the ultra-high sensitivity and extremely low detection limit of CdSe SC based detectors make their application prospects very promising. [ABSTRACT FROM AUTHOR]

Low‐dimensional perovskites (LDPs) have attracted significant attention due to their high stability, great chemical flexibility, and fertile "playground" for structural modulation, which are expected to herald the next‐generation multifunctional devices. While there is a high diversity of LDPs in the literature, the organic cations in most of the literature are still limited to amines. Here, the preparation of centimeter‐sized LDP single crystals with amidino‐based spacers is described, which enables systematic investigations on how halides initiate different structural stacking and on their physical properties. The 4‐amidinopyridine (4AP) cation in (4AP)PbX4 (X = Br, I) is vertically distributed between the inorganic layers to form a two‐dimensional perovskite. While the Cl‐based exhibits one‐dimensional perovskitoid packing. The change of halogens from Cl to Br and I leads to a lower hydrogen bonding, hardness and activation energy of the crystal. Finally, the potential of these crystals for X‐ray detectors is demonstrated. The (4AP)PbBr4 device achieves the highest sensitivity among three devices (373.1 µC Gyair−1 cm−2, 10 V), benefiting from the balanced charge transport and ionic migration. It is anticipated that this work will lead to further studies on the exploration and physics of novel LDP with properties suitable for radiation detection. [ABSTRACT FROM AUTHOR]

Detecting low dose rates of X-rays is critical for making safer radiology instruments, but is limited by the absorber materials available. Here, we develop bismuth oxyiodide (BiOI) single crystals into effective X-ray detectors. BiOI features complex lattice dynamics, owing to the ionic character of the lattice and weak van der Waals interactions between layers. Through use of ultrafast spectroscopy, first-principles computations and detailed optical and structural characterisation, we show that photoexcited charge-carriers in BiOI couple to intralayer breathing phonon modes, forming large polarons, thus enabling longer drift lengths for the photoexcited carriers than would be expected if self-trapping occurred. This, combined with the low and stable dark currents and high linear X-ray attenuation coefficients, leads to strong detector performance. High sensitivities reaching 1.1 × 103 μC Gyair−1 cm−2 are achieved, and the lowest dose rate directly measured by the detectors was 22 nGyair s−1. The photophysical principles discussed herein offer new design avenues for novel materials with heavy elements and low-dimensional electronic structures for (opto)electronic applications. The complex coupling between charge-carriers and phonons in bismuth oxyiodide (BiOI) are uncovered, showing how carrier localisation is avoided and long transport lengths achieved. As a result, BiOI is revealed to be highly effective for X-ray detection. [ABSTRACT FROM AUTHOR]

CsI(Tl) scintillator has been widely used in X-ray flat-panel detectors due to excellent performance characteristics including a suitable Si-photodiode emission wavelength, excellent optical output, and fast decay time. Here, a solution-based space-confined growth method was presented to achieve CsI(Tl) scintillator single-crystal flakes with controllable thickness. The grown CsI(Tl) single-crystal flake exhibits a comparable light yield (∼72,000 photons/MeV) and a lower afterglow level (0.1% @ 21 ms, 0.01% @ 118 ms) in comparison to that by the traditional melting method. This space-confined method allows for the achievement of a single crystal thickness of only 0.27 mm, making it suitable for direct application in X-ray detection and other related fields. It may open up new possibilities for the development of halide scintillator single crystals. A solution-based space-confined growth method enables the growth of high-quality CsI(Tl) single crystal flakes with controlled thickness for X-ray flat-panel detectors. [Display omitted] • A space-confined solution method is used to grown CsI(Tl) single-crystal flakes. • The thickness of the CsI(Tl) flake grown using this method can be controlled to be as thin as approximately 0.27 mm. • The CsI(Tl) flake exhibits a lower afterglow and a comparable light yield in comparison to that by the melting method. [ABSTRACT FROM AUTHOR]

Perovskite X-ray detectors are actively investigated because of their exceptional properties, including their significant attenuation coefficient, low defect density, excellent transport characteristics, easy growth, and high sensitivity to X-ray photons. However, perovskite-based high-energy X-ray detectors on the MeV scale are rarely explored. In this study, we investigate the optoelectronic characteristics and radiation detection capabilities of triple-cation Cs 0.05 FA 0.9 MA 0.05 PbI 3 single crystals (CSC) grown using the inverse temperature crystallization method. The CSCs with a reduced Goldschmidt tolerance factor owing to the presence of Cs and MA ions exhibit exceptional properties, including a bandgap of 1.447 eV, low dark current, and self-powered response to X-ray irradiation. The X-ray absorption rate of 36 keV exceeded 99% with a CSC thickness of 2 mm, demonstrating its strong stopping power. Moreover, the CSC detectors exhibit precise linear responses to varying X-ray doses and dose rates with R2 values close to 1 and relative standard deviation (RSD) values below 3% under all the tested conditions. In addition, the detector effectively detected high-energy X-rays of up to 15 MV with minimal variations in the RSD values. These findings highlight the potential of CSC as promising materials for high-performance X-ray detectors. • Triple-cation lead–halide perovskites for high-energy X-ray detection were studied. • CSC detector has uniform linear response to varying X-ray doses and rates. • CSC detector can detect high-energy X-rays of up to 15 MeV. • CSC demonstrated remarkable promise as excellent self-powered X-ray detectors. [ABSTRACT FROM AUTHOR]

Hybrid bismuth halides perovskites have emerged as promising candidates for X‐ray detection, due to the strong absorptivity of high‐energy X‐ray photons, high resistivity, large carrier diffusion length and low toxicity. However, the mostly investigated hybrid bismuth iodides single crystals are usually opaque and require a harsh synthesis process. Herein, novel one‐dimensional (1D) pentamethylenediamine bismuth bromide (PDA)BiBr5 single crystals were synthesized via an antisolvent‐assisted crystallization method at room temperature. Bulk (PDA)BiBr5 single crystals have sizes of 10×1.3×1.5 mm3 and high transparency. They are shown to have low density of defects of 2.0×1010 cm−3 and obvious photoconductivity. Moreover, they exhibit large bulk resistivity of 2.13×1011 Ω cm and good X‐ray attenuation coefficient. Consequently, the vertical structured (PDA)BiBr5 single crystal X‐ray photoconductor produces a sensitivity of 3.8 μC Gyair−1 cm−2. This study provides a facile strategy for synthesizing bulk hybrid bismuth bromides single crystals with potential X‐ray detection application. [ABSTRACT FROM AUTHOR]

The recently demonstrated Cs3Bi2I9 single crystals (SCs) exhibit superior performance for X‐ray detection. More importantly, they do not contain any toxic lead element. However, compared with lead‐halide perovskites, one challenge for the Cs3Bi2I9 SC for X‐ray detection application is that it is difficult to prepare large‐sized and high‐quality SCs. Here, a liquid diffused separation induced crystallization (LDSC) method is employed to grow Cs3Bi2I9 SCs for eliminating the temperature fluctuation and convection currents caused by the thermal gradient in the growth solution. The resultant Cs3Bi2I9 SC exhibits a microstrain of 1.21 × 10–3, a resistivity of 1.12 × 109 Ω cm, a carrier mobility of 4.57 cm2 V–1 s–1, and a mobility‐lifetime product of 1.87 × 10–3 cm2 V–1. As a result, an X‐ray detector based on the high‐quality Cs3Bi2I9 SC exhibits an excellent dose rate linearity, a sensitivity of 964 µC Gyair–1 cm–2, and a limit of detection (LoD) of 44.6 nGyair s–1. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) hybrid perovskite single crystals are promising photovoltaic materials. However, the single crystals grown from solution usually respond poorly to light and other charged particles. The 2D (BDA)CsPb 2 Br 7 single crystals (BDA = 1,4-butanediamine) are grown from a supersaturated solution. The macroscopical growth steps are present on the surface, leading to a large leakage current during device operation. The surface defects are removed to expose a clean and flat surface. This well-defined crystallographic surface enables an Ohmic contact with the electrode, which minimized the dark current and baseline drift. Consequently, the assembled devices exhibit an enhanced response to LED light and X-rays, revealing the surface defect to be one of the culprits underneath the poor performance of solution-grown perovskite single crystals. • The (BDA)CsPb 2 Br 7 perovskite single crystal was grown by solution cooling method. • Surface defects worsen the detection performance of crystals for photons and X-rays. • A surface treatment method was used to remove defects and improve device performance. [ABSTRACT FROM AUTHOR]