μC Gyair Research Articles

APbI3-A2AgBiI6 Double-Layer Perovskite Film for a Self-Powered and High-Stability X-ray Detector.

The development of lead halide perovskite X-ray detectors has promising applications in medical imaging and security inspection but is hindered by poor long-term stability and drift of the dark current and photocurrent. Herein, we design a (Cs0.05MA0.65FA0.3)PbI3-(Cs0.1MA1.3FA0.6)AgBiI6 double-layer perovskite film to assemble a self-powered flat-panel X-ray detector. The demonstrated X-ray detector achieves an outstanding self-powered sensitivity of 80 μC Gyair-1 cm-2 under a 0 V bias. More importantly, owing to the inhibition of the phase transition process and ion migration of (Cs0.05MA0.65FA0.3)PbI3 by the (Cs0.1MA1.3FA0.6)AgBiI6 layer, the device exhibits excellent continuous operating stability with a retention rate of 99% dark current and photocurrent over X-ray pulses of up to 4000 s and excellent long-term stability without a loss of the original response current after 150 days in an air environment. The strategy of double-layer perovskites improves the stability and sensitivity of devices, which paves a path for the industrial application of lead halide perovskite X-ray detectors.

One-Dimensional orthorhombic CsPbI3 polycrystalline thick film for efficient and highly stable direct X-ray detection and imaging

An ideal direct X-ray detector should convert a low dose of X-ray photons into large quantity of electrical signals, coupled with sustained long-term stability. Nevertheless, a notable conflict arises between X-ray absorption efficiency and carrier transport in thick polycrystalline perovskite films. Moreover, conventional perovskite materials exhibit inherent challenges regarding the stability of their crystal phase and the consistency of the photocurrent. To circumvent these limitations, a polycrystalline perovskite thick film is proposed using orthorhombic CsPbI3 (δ-CsPbI3) as a highly stable active material. Combined with the liquid epitaxy process, δ-CsPbI3 prefers one-dimensional growth along the carrier transportation direction, which suppresses the formation of grain boundaries, enabling high carrier mobility while maintaining X-ray absorption for a thick polycrystalline film. Consequently, the polycrystalline δ-CsPbI3 based detector exhibits a highest sensitivity of 1768.46 μC Gyair-1 cm−2 at an electric field of 432 V mm−1 which is 88.42-fold higher than α-Se based detectors and 190-fold higher than the single crystalline δ-CsPbI3 based detector, respectively. The sensitivity maintains 91.34 % of its initial state after 7 days exposure in the air. Combing with a thin-film transistor array, the detector achieves 8-bit imaging within a 64 × 64 matrix. This work provides a feasible method for commercialized production of high-performance direct X-ray detectors.

High-Performance Flat-Panel Perovskite X-ray Detectors Enabled by Defect Passivation in Ruddlesden-Popper Perovskites.

Halide perovskites have emerged as promising candidates in X-ray detection due to their strong X-ray absorption and excellent optoelectronic properties. The development of sensitive and stable flat-panel X-ray detectors with high resolution is crucial for practical applications. In this paper, we introduce a novel flat-panel X-ray detector that integrates quasi-two-dimensional (2D) Ruddlesden-Popper (RP) perovskite with a pixeled thin film transistor (TFT) backplane. We incorporate 2,5-dibromopyrimidine (DBPM) as an additive to passivate the Lewis acid defects in the quasi-2D RP perovskite. This modification results in suppressed ion migration, improved optoelectronic performance, and enhanced operational stability of the device. Impressively, the activation energy of the RP perovskite increases from 0.96 to 1.35 eV with the DBPM additive. As a result, X-ray detectors exhibit a high sensitivity of ∼13,600 μC Gyair-1 cm-2, a low detection limit of 6.56 nGyair s-1, and excellent operational stability. Moreover, the flat-panel detectors demonstrate a high spatial resolution of 3.7 line pairs per millimeter and excellent X-ray imaging properties under a remarkably low X-ray dose of ∼50 μGyair, which is just half of the X-ray dose typically used in commercial equipment. This study opens new avenues for the development of flat-panel perovskite X-ray detectors with significant potential for various applications.

Structure design of lead-free chiral-polar perovskites for sensitive self-powered X-ray detection

Metal halide perovskites have made significant progress in X-ray detection owing to their exceptional optoelectronic properties. However, most of these materials suffer from toxic element lead and require for high operating voltages. Hence, it is imperative to explore environmentally friendly perovskite crystals without external bias for X-ray detection. Herein, we strategically introduce chiral cations to synthesize a pair of lead-free chiral-polar hybrid perovskites (S-MPz)6Bi3I21·6H2O and (R-MPz)6Bi3I21·6H2O (1S and 1R, S/R-MPz = S/R-2-methylpiperazinium), which exhibit strong circular dichroism (CD) signals with an anisotropic g-factor reaching approximately 0.017. Significantly, the chiral-polar feature gives rise to distinctive spontaneous polarization, which leads to a photovoltage of 1.1 V under X-ray illumination, endowing self-powered detection capabilities for X-ray. Further exploration of X-ray devices based on 1R single crystal (SC) demonstrates a high sensitivity of 5.2 μC Gyair−1 cm−2 at zero bias. This study realizes passive X-ray detection depending on the intrinsic spontaneous polarization induced built-in electric field of chiral-polar perovskite, providing an effective approach to the chemical design of desired materials for high-performance “green” self-powered radiation detection.

Dynamic X-ray imaging with screen-printed perovskite CMOS array.

High performance X-ray detector with ultra-high spatial and temporal resolution are crucial for biomedical imaging. This study reports a dynamic direct-conversion CMOS X-ray detector assembled with screen-printed CsPbBr3, whose mobility-lifetime product is 5.2 × 10-4 cm2 V-1 and X-ray sensitivity is 1.6 × 104 µC Gyair-1 cm-2. Samples larger than 5 cm[Formula: see text]10 cm can be rapidly imaged by scanning this detector at a speed of 300 frames per second along the vertical and horizontal directions. In comparison to traditional indirect-conversion CMOS X-ray detector, this perovskite CMOS detector offers high spatial resolution (5.0 lp mm-1) X-ray radiographic imaging capability at low radiation dose (260 nGy). Moreover, 3D tomographic images of a biological specimen are also successfully reconstructed. These results highlight the perovskite CMOS detector's potential in high-resolution, large-area, low-dose dynamic biomedical X-ray and CT imaging, as well as in non-destructive X-ray testing and security scanning.

Toward Low-Voltage and High-Sensitivity Direct X-ray Detectors Based on Thick Bulk Heterojunction Organic Device.

Organic semiconducting materials are promising for the fabrication of flexible ionizing radiation detectors for imaging because of their tissue equivalence, simple large-scale processing, and mass production. However, it is challenging to achieve high-sensitivity detection for organic direct detectors prepared by low-cost solution processing because of the compromise between thickness and carrier transport. In this study, high-performance organic direct X-ray detectors were fabricated by building a micrometer-thick bulk heterojunction (BHJ) using poly(3-hexylthiophene-2,5-diyl) (P3HT):(6,6)-phenyl c71 butyric acid methyl ester. A 5 μm BHJ film was fabricated by drop-casting and enhanced crystallization of P3HT using binary solvents and high-boiling-point additives to improve the charge carrier mobility. Furthermore, this organic direct X-ray detector has a sensitivity of >654.26 μC Gyair s-1 and a self-powered response. Because of the architecture of the thick active layer and the energy cascade in this diode detector, it has a very low dark current of 46.26 pA at -2 V. A fast and efficient approach was developed for fabricating thick, highly mobile organic BHJ films for high-performance direct X-ray detectors. It has great potential for application in a new generation of flexible and portable large-area flat-panel detectors.

Halogen-Regulated Tc and X-ray Radiation Detection in 2D Hybrid Perovskite Ferroelastic Semiconductor.

Organic-inorganic hybrid perovskites (OIHPs) have received particular attention due to their characteristic structural tunability and flexibility. These features make OIHPs behave with excellent modifications on macroscopic properties, such as ferroicity or semiconductor performances, etc. Herein, we report two 2D hybrid stibium-based halide perovskite (C3H7N)3Sb2X9 (X = Br, 1; Cl, 2) ferroelastic semiconductor possessing dual switching properties of dielectric and second harmonic generation (SHG). Notably, these two hybrids exhibit halogen-regulated ferroelasticity and semiconductor properties. There is a significant difference in Curie temperature (Tc) and X-ray radiation detection sensitivity (S), i.e., the ΔTc and ΔS are 38 K and 87 μC Gyair-1 cm-2, respectively. Meanwhile, crystals 1 and 2 do not show dark current drift in cyclic measurements of different radiation doses with stable switching ratios of 30 and 10, separately. Meanwhile, these results were proven by scientific experimental results and density functional theory (DFT) calculations. Our work presents a facile and practical method to regulate macroproperties on the molecular level, providing a new vision to develop hybrid perovskite ferroic-photoelectric materials.

Aging CsPbBr3 Nanocrystal Wafer for Ultralow Ionic Migration and Environmental Stability for Direct X-ray Detection.

The outstanding photoelectric properties of perovskites demonstrate extreme promise for application in X-ray detection. However, the soft lattice of the perovskite results in severe ionic migration for three-dimensional materials, limiting the operation stability of perovskite X-ray detectors. Although ligand-decorated nanocrystals (NCs) exhibit significantly higher stability than three-dimensional perovskites, defects remaining on the interface of NCs could still trigger halide migration under a high bias due to the incomplete ligand decoration. Furthermore, it is still challenging to realize sufficient thickness of absorption layers based on NCs for X-ray detectors through traditional methods. Herein, we develop a centimeter-size and millimeter-thick wafer based on CsPbBr3 NCs through isostatic pressing for X-ray detectors, in which the interfacial defects of NCs are remedied by CsPb2Br5 during aging of wafer in ambient humidity. The wafer shows outstanding sensitivity (200 μC Gyair-1 cm-2) and ultralow dark current drift (1.78 × 10-8 nA cm-1 s-1 V-1 @ 400 V cm-1). Moreover, it shows storage stability with negligible performance degradation for 60 days in ambient humidity. Thus, aging perovskite NC wafers for X-ray detection holds huge potential for next-generation X-ray imaging plates.

Efficient Direct X-ray Detection and Imaging Based on a Lead-Free Electron Donor-Acceptor MOF.

Metal-organic frameworks (MOFs) have recently gained extensive attention as potential materials for direct radiation detection due to their strong radiation absorption, long-range order, and chemical tunability. However, it remains challenging to develop a practical MOF-based X-ray direct detector that possesses high X-ray detection efficiency, radiation stability, and environmental friendliness. The integration of donor-acceptor (D-A) pairs into crystalline MOFs is a powerful strategy for the precise fabrication of multifunctional materials with unique optoelectronic properties. Herein, a new lead-free MOF, Cu2I2(TPPA) (CuI-TPPA, TPPA = tris[4-(pyridine-4-yl)phenyl]amine), with a 6-fold interpenetrated structure is designed and synthesized based on the electron donor-acceptor strategy. CuI-TPPA has a large mobility-lifetime (μτ) product of 5.8 × 10-4 cm2 V-1 and a high detection sensitivity of 73.1 μC Gyair-1 cm-2, surpassing that of commercial α-Se detectors. Moreover, the detector remains fairly stable with only a 2% reduction in photocurrent under continuous bias irradiation conditions with a total dose of over 42.83 Gyair. The CuI-TPPA/poly(vinylidene fluoride) flexible composite X-ray detector films are successfully manufactured with different thicknesses. Through multifaceted assessments, the optimal thickness is found with a high detection sensitivity of up to 143.6 μC Gyair-1 cm-2. As proof-of-concept, 11 × 9 pixelated X-ray detectors are fabricated on the same composite film to realize X-ray direct imaging. This work opens up potential applications of MOFs in environmentally friendly and wearable devices for direct X-ray detection and imaging.

2D CuInP2Se6 in High‐Sensitivity UV‐vis And X‐Ray Detection

AbstractMetal thio(seleno)phosphates are renowned for their multifaceted physical characteristics and versatile applications, particularly in optoelectronics. In detection applications, a low and stable dark current is crucial, enhancing the sensitivity and signal‐to‐noise ratio of detectors. Herein, a van der Waals layered material has synthesized, CuInP2Se6. Despite its nanometric scale, 2D CuInP2Se6 detector transcends the conventional absorption inefficiencies tied to ultrathin materials. It delivers exceptional ultraviolet–visible detection, characterized by an ultralow, stable dark current of 150 fA, and a noise power density of 27.7 fA Hz−1/2 at room temperature. The in‐depth investigation reveals a responsivity of 4.47 A W−1, an external quantum efficiency of 1369%, a special detectivity of 1.44 × 1013 Jones, and a rapid response speed of 280 µs, positioning it at the pinnacle of 2D photodetector performance. The CuInP2Se6’s ultralow, stable dark current paves the way for X‐ray detection, achieving an unprecedented sensitivity of 1.32 × 105 µC Gyair−1 cm−2 and a low detection limit of 0.15 µGyair s−1. Furthermore, 2D CuInP2Se6 detector exhibits a remarkable image‐sensing capability, adeptly capturing intricate patterns with high resolution. This discovery indicates its promise in revolutionizing integrated micro/nano optoelectronic devices, opening avenues for advancements in light and X‐ray detection and imaging technologies.

Self‐Cleaning Perovskite Single Crystals Fabricated with Bis(trifluoromethylsulfonyl)imide Derived Ionic Liquid Toward High‐Performance Photodetection

AbstractSurface defects are crucial to perovskite single crystals (SCs) for versatile optoelectronic applications, whereas suffers from the intricate post‐treatments and unsatisfactory reproducibility within solution growth strategy due to the residue solvent corrosion and adsorbed precursors deposition. Here, an ionic liquid, 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (BMITFSI) is demonstrated, assisted solution growth approach for fabricating high‐quality self‐cleaning perovskite single crystals with no need for any post‐treatment. Benefiting from the in situ assembling in crystalline surface, BMITFSI can effectively decrease the crystallographic trap density by simultaneously introducing the self‐cleaning effect and optimizing the crystalline growth process. Particularly, as fabricated MAPbI3 single crystal exhibits an impressive photodetection performance with a specific detectivity of 2.83 × 1012 Jones in visible‐IR spectrum and a sensitivity of 7.24 × 104 µC Gyair−1 cm−2 in X‐ray detection, which is as good as the conventionally fabricated crystal with elaborate post‐treatments. Based on the chemical composition independent universality, this work paves an easy but efficient route to improve the current crystallization methodology toward high‐quality perovskite SCs fabrication.

Cation-π interactions enabled water-stable perovskite X-ray flat mini-panel imager

Sensitive and stable perovskite X-ray detectors are attractive in low-dosage medical examinations. The high sensitivity, tunable chemical compositions, electronic dimensions, and low-cost raw materials make perovskites promising next-generation semiconductors. However, their ionic nature brings serious concerns about their chemical and water stability, limiting their applications in well-established technologies like crystal polishing, micro-processing, photolithography, etc. Herein we report a one-dimensional tryptamine lead iodide perovskite, which is stable in water for several months as the strong cation-π interactions between organic cations. The one-dimensional and two-dimensional tryptamine lead iodide perovskite tablets are switchable through thermal-annealing or water-soaking treatments to relax microstrains. The water-stable and microstrain-free one-dimensional perovskite tablets yield a large sensitivity of 2.5 × 106 μC Gyair−1 cm−2 with the lowest detectable dose rate of 5 nGyair s−1. Microelectrode arrays are realized by surface photolithography to construct high-performance X-ray flat mini-panels with good X-ray imaging capability, and a record spatial resolution of 17.2 lp mm−1 is demonstrated.

Tetraphenylene-based semiconductive metal-organic framework crystals for direct X-ray detection and imaging.

MOFs have good potential for X-ray detection, but direct X-ray detection in single crystal form is rarely reported. In this work, we successfully synthesized Pb-TCPE, and the single crystal achieves a low detection limit and high detection sensitivity of 4812.6 μC Gyair-1 cm-2, which exhibits great potential for X-ray detection and imaging.

Enhanced exciton-phonon coupling in pseudohalide 2D perovskite for X-ray to visible light detection.

Two-dimensional Cs2Pb(SCN)2I2 perovskite has an ultra-small interlayer spacing, inducing a series of interesting semiconductor properties, such as efficient interlayer carrier transport as well as lower exciton binding energy compared to perovskites with long alkylammonium cations. The prepared Cs2Pb(SCN)2I2 photodetector achieves a high on/off ratio of 2.1 × 104 with a specific detectivity of 6.2 × 1011 jones to 450 nm visible light, and a high sensitivity of 2747 μC Gyair-1 cm-2 to X-rays.

Exploring centimeter-sized single crystals of a 2D Dion–Jacobson halide perovskite toward efficient X-ray detection

A 2D halide perovskite (1) was syntheized. 1 shows semiconductor properties, such as a high resistivity (6.01 × 1010 Ω cm) and a μτ product (6.21 × 10−4 cm2 V−1), a low LOD of 236 nGyair s−1 and a sensitivity of 270 μC Gyair−1 cm−2 at a 5 V bias.

Oriented Heterodimensional Perovskite Crystals for Self‐Powered X‐Ray Detection with Reduced Dark Current and Anisotropic Response

AbstractX‐ray detectors utilizing 2D/3D heterodimensional perovskites have achieved great success. However, the labile nature of halide perovskites generally results in structures with random orientations and interfaces, which in turn increases the dark noise of X‐ray detectors, hindering their use in low‐dose X‐ray detection. Here, it is shown that both anisotropy and ultralow dark current can be achieved in self‐powered X‐ray detectors using well‐oriented 2D/3D heterodimensional perovskite crystals (HPCs). A halide diffusion‐promoted welding approach is devised to create the oriented HPCs, enabling two distinct configurations: A lateral orientation where the inorganic frameworks of the two phases are perpendicular, and a vertical orientation with parallel inorganic slabs. The different crystalline orientations produce unique anisotropic X‐ray detecting performance of 2D/3D HPCs, with a large anisotropic ratio of 4. Moreover, a self‐powered X‐ray detector using vertical HPC exhibits a greatly suppressed dark current density of 0.17 nA cm−2 and a low detection limit of 77 nGyair s−1, enabling high‐resolution X‐ray imaging. In contrast, the lateral devices show higher X‐ray sensitivity (1850 µC Gyair−1cm−2) at zero bias. This work reveals the interplay between crystalline orientation and X‐ray detection performance, opening new possibilities for developing low‐cost, low‐noise X‐ray detectors.

Aligned Conjugated Polymer Nanofiber Networks in an Elastomer Matrix for High-Performance Printed Stretchable Electronics.

Conjugated polymer films are promising in wearable X-ray detection. However, achieving optimal film microstructure possessing good electrical and detection performance under large deformation via scalable printing remains challenging. Herein, we report bar-coated high-performance stretchable films based on a conjugated polymer P(TDPP-Se) and elastomer SEBS blend by optimizing the solution-processing conditions. The moderate preaggregation in solution and prolonged growth dynamics from a solvent mixture with limited dissolving capacity is critical to forming aligned P(TDPP-Se) chains/crystalline nanofibers in the SEBS phase with enhanced π-π stacking for charge transport and stress dissipation. The film shows a large elongation at break of >400% and high mobilities of 5.29 cm2 V-1 s-1 at 0% strain and 1.66 cm2 V-1 s-1 over 500 stretch-release cycles at 50% strain, enabling good X-ray imaging with a high sensitivity of 1501.52 μC Gyair-1 cm-2. Our work provides a morphology control strategy toward high-performance conjugated polymer film-based stretchable electronics.

Halide Perovskites and Their Derivatives for Efficient, High-Resolution Direct Radiation Detection: Design Strategies and Applications.

The past decade has witnessed a rapid rise in the performance of optoelectronic devices based on lead-halide perovskites (LHPs). The large mobility-lifetime products and defect tolerance of these materials, essential for optoelectronics, also make them well-suited for radiation detectors, especially given the heavy elements present, which is essential for strong X-ray and γ-ray attenuation. Over the past decade, LHP thick films, wafers, and single crystals have given rise to direct radiation detectors that have outperformed incumbent technologies in terms of sensitivity (reported values up to 3.5×106 µC Gyair -1 cm-2 ), limit of detection (directly measured values down to 1.5 nGyair s-1 ), along with competitive energy and imaging resolution at room temperature. At the same time, lead-free perovskite-inspired materials (e.g., methylammonium bismuth iodide), which have underperformed in solar cells, have recently matched and, in some areas (e.g., in polarization stability), surpassed the performance of LHP detectors. These advances open up opportunities to achieve devices for safer medical imaging, as well as more effective non-invasive analysis for security, nuclear safety, or product inspection applications. Herein, the principles behind the rapid rises in performance of LHP and perovskite-inspired material detectors, and how their properties and performance link with critical applications in non-invasive diagnostics are discussed. The key strategies to engineer the performance of these materials, and the important challenges to overcome to commercialize these new technologies are also discussed.

Molecular Design of Layered Hybrid Silver Bismuth Bromine Single Crystal for Ultra-Stable X-Ray Detection With Record Sensitivity.

Nowadays, weak interlayer coupling and unclear mechanism in layered hybrid silver bismuth bromine (LH-AgBiBr) are the main reasons for limiting its further enhanced X-ray detection sensitivity and stability. Herein, the design rules for LH-AgBiBr and its influence on X-ray detection performance are reported for the first time. Although shortening amine size can enhance interlayer coupling, its detection performance is severely hampered by its easier defect formation caused by enlarged micro strain. In contrast, an appropriate divalent amine design endows the material with improved interlayer coupling and released micro strain, which benefits crystal stability and mechanical hardness. Another contribution is to increase material density and dielectric constant; thus, enhancing X-ray absorption and carrier transport. Consequently, the optimized parallel device based on BDA2 AgBiBr8 achieves a record sensitivity of 2638 µC Gyair -1 cm-2 and an ultra-low detection limit of 7.4 nGyair s-1 , outperforming other reported LH-AgBiBr X-ray detectors. Moreover, the unencapsulated device displays remarkable anti-moisture, anti-thermal (>150 °C), and anti-radiation (>1000 Gyair ) endurance. Eventually, high-resolution hard X-ray imaging is demonstrated by linear detector arrays under a benign dose rate (1.63 µGyair s-1 ) and low external bias (5V). Hence, these findings provide guidelines for future materials design and device optimization.

Heterointerface Design of Perovskite Single Crystals for High-Performance X-Ray Imaging.

Metal halide perovskite single crystals (MHP-SCs) are known for their facile fabrication into large sizes using inexpensive solution methods. Owing to their combination of large mobility-lifetime products and strong X-ray absorption, they are considered promising materials for efficient X-ray detection. However, they suffer from large dark currents and severe ion migration, which limit their sensitivity and stability in critical X-ray detection applications. Herein, a heterointerface design is proposed to reduce both the dark current and ion migration by forming a heterojunction. In addition, the carrier transport performance is significantly improved using heterointerface engineering by designing a gradient band structure in the SCs. The SC heterojunction detectors exhibit a high sensitivity of 3.98 × 105 µC Gyair -1 cm-2 with a low detection limit of 12.2 nGyair s-1 and a high spatial resolution of 10.2 lp mm-1 during imaging. These values are among the highest reported for state-of-the-art MHP X-ray detectors. Moreover, the detectors show excellent stability under continuous X-ray irradiation and maintainclear X-ray imaging after 240 d. This study provides novel insights into the design and fabrication of X-ray detectors with high detection efficiency and stability, which are beneficial for developing inexpensive, high-resolution X-ray imaging equipment.