Vertically Oriented Quasi-2D Perovskite Grown In-Situ by Carbonyl Array-Synergized Crystallization for Direct X-Ray Detectors.

Quasi-2D perovskite quantum wells are increasingly recognized as promising candidates for direct-conversion X-ray detection. However, the fabrication of oriented and uniformly thick quasi-2D perovskite films, crucial for effective high-energy X-ray detection, is hindered by the inherent challenges of preferential crystallization at the gas-liquid interface, resulting in poor film quality. In addressing this limitation, a carbonyl array-synergized crystallization (CSC) strategy is employed for the fabrication of thick films of a quasi-2D Ruddlesden-Popper (RP) phase perovskite, specifically PEA2MA4Pb5I16. The CSC strategy involves incorporating two forms of carbonyls in the perovskite precursor, generating large and dense intermediates. This design reduces the nucleation rate at the gas-liquid interface, enhances the binding energies of Pb2+ at (202) and (111) planes, and passivates ion vacancy defects. Consequently, the construction of high-quality thick films of PEA2MA4Pb5I16 RP perovskite quantum wells is achieved and characterized by vertical orientation and a pure well-width distribution. The corresponding PEA2MA4Pb5I16 RP perovskite X-ray detectors exhibit multi-dimensional advantages in performance compared to previous approaches and commercially available a-Se detectors. This CSC strategy promotes 2D perovskites as a candidate for next-generation large-area flat-panel X-ray detection systems.

Polycrystalline Lead-Free Perovskite Direct X-Ray Detectors with High Durability and Low Limit of Detection via Low-Temperature Coating.

Direct X-ray detectors represent a transformative technology in the realm of radiography and imaging. The double halide-based perovskite cesium silver bismuth bromide (Cs2AgBiBr6) has emerged as a promising material for use in direct X-ray imaging, owing to its nontoxic composition, strong X-ray absorption, decent charge mobility lifetime product (µτ), and low-cost preparation. However, formidable issues related to scalability and ion migration, stemming from intrinsic factors such as halogen vacancies and grain boundaries, have presented significant impediments. These issues have been associated with substantial noise, baseline instability, and a curtailment of detection performance. In response to these multifaceted challenges, we propose a slurry-based in situ treatment technique for fabricating robust Cs2AgBiBr6 thick films. This novel approach adeptly mitigates halogen vacancies, actively passivates grain boundaries, and concurrently elevates the ion migration activation energy, thus effectively suppressing ion migration. Consequently, the obtained X-ray detector exhibits excellent operating stability with minimal signal drift of 8.5 × 10-9 nA cm-1 s-1 V-1 and achieves a remarkable 385% increase in sensitivity with a limit of detection as low as 7.8 nGyair s-1. These results mark a significant step toward the development of high-performance and long-lasting lead-free perovskite direct X-ray detectors.

Large lateral photovoltaic effect with ultrafast optical relaxation time in SnS2/n-Si junctions.

A large lateral photovoltaic effect (LPE) with a fast optical response time is necessary to develop high-performance position-sensitive detectors. In this paper, we report an LPE with a high self-powered position sensitivity and ultrafast optical relaxation time in S n S 2/n-S i junctions prepared using pulsed laser deposition. A large built-in electric field was generated at the S n S 2/S i interface, which resulted in a large LPE with a positional sensitivity of up to 116 mV/mm. Furthermore, the measurement circuit with multiple parallel resistors had a strong influence on the ultrafast optical response time of the LPE and the fastest optical relaxation time observed was ∼0.44µs. Our results suggest that the S n S 2/S i junction would be a promising candidate for a wide range of optoelectronic device applications.

The impact of oxygen on Ga doped ZnO film.

The Ga doped ZnO (GZO) film is one of the promising alternative films to replace ITO film, but its properties suffer from degradation when it is deposited under oxygen-rich conditions. This degradation has been investigated by depositing the films under different oxygen partial pressures. XRD results showed that all GZO films had wurtzite structure and the lattice parameter-c contracted when oxygen was introduced into the argon deposition atmosphere, but the parameter-c nearly remained constant when oxygen partial pressures were further increased. The contraction of parameter-c was caused by the increasing concentrations of VZn (Zn vacancy). It was the first time to observe that the impurity phase of Ga2Zn6O9 appeared and disappeared in GZO films during the increase of oxygen partial pressures. Analogously, conductivity decayed and optical bandgap decreased abruptly as oxygen was introduced, which enhanced self-compensation of donors and acceptors. The energy band structures of GZO and ZnO films were determined by using UPS, and the results showed that oxygen had little effect on the electron affinity of the GZO film, but a significant difference in electron affinity between the ZnO and GZO films was observed. This result indicated that although the electron affinity of ZnO could be effectively tuned by doping with Ga, it remained quite stable for GZO under oxygen-rich conditions.

Synergistic Ionic Liquid in Hole Transport Layers for Highly Stable and Efficient Perovskite Solar Cells.

Perovskite solar cells (PSCs) with n-i-p structures often utilize an organic 2,2',7,7'-tetrakis (N, N-di-p-methoxyphenyl-amine) 9,9'-spirobifluorene (spiro-OMeTAD) along with additives of lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI) and tert-butylpyridine as the hole transporting layer (HTL). However, the HTL lacks stability in ambient air, and numerous defects are often present on the perovskite surface, which is not conducive to a stable and efficient PSC. Therefore, constructive strategies that simultaneously stabilize spiro-OMeTAD and passivate the perovskite surface are required. In this work, it is demonstrated that a novel ionic liquid of dimethylammonium bis(trifluoromethanesulfonyl)imide (DMATFSI) could act as a bifunctional HTL modulator in n-i-p PSCs. The addition of DMATFSI into spiro-OMeTAD can effectively stabilize the oxidized spiro-OMeTAD+ cation radicals through the formation of spiro-OMeTAD+ TFSI- because of the excellent charge delocalization of the conjugated CF3 SO2 - moiety within TFSI- . In addition, DMA+ cations could move toward the perovskite from the HTL, resulting in the passivation of defects at the perovskite surface. Accordingly, a power conversion efficiency of 23.22% is achieved for PSCs with DMATFSI and LiTFSI co-doped spiro-OMeTAD. Moreover, benefiting from the improved ion migration barrier and hydrophobicity of the HTL, still retained nearly 80% of their initial power conversion efficiency after 36 days of exposure to ambient air.

A geometric alignment for human temporal bone CT images via lateral semicircular canals segmentation.

PURPOSE: Due to the different posture of the subject and settings of CT scanners, the CT images of the human temporal bone should be geometrically aligned with multiplanar reconstruction to ensure the symmetry of the bilateral anatomical structure. Manual alignment is a time-consuming task for radiologists and an important preprocessing step for further computer-aided CT analysis. We propose a fully automatic alignment algorithm for temporal bone CT images via lateral semicircular canals (LSCs) segmentation. METHODS: The LSCs are segmented with our proposed multifeature fusion network as anchors at first. Then, we define a standard 3D coordinate system and propose an alignment procedure. RESULTS: The experimental results show that our LSC segmentation network achieved a higher segmentation accuracy. The acceptable rate is achieved 85% over 910 raw temporal bone CT sequences. The alignment speed is reduced from 10 min by manual to 60s. CONCLUSIONS: Aiming at the problem of bilateral asymmetry in the raw temporal bone CT images, we propose an automatic geometric alignment method. Our proposed method can help to perform alignment of temporal bone CT images efficiently.

Labyrinth net: A robust segmentation method for inner ear labyrinth in CT images.

The inner ear labyrinth is a combined sensory organ of hearing and balance, which is surrounding the bony cavity located in the petrous temporal bone. The structure of the inner ear labyrinth plays an important role in otology research and clinic diagnosis of ear diseases. Automatic and accurate segmentation of the inner ear labyrinth is a foundation of computer-aided temporal bone quantitively measurements and diagnosis. The inner ear labyrinth is characterized by its complex morphology, small size, and high labeling cost, which brings challenges for deep learning-based automatic segmentation methods. In this paper, we propose a robust segmentation method for the labyrinth in temporal bone CT images via multi-model inconsistency. In the active-learning paradigm, we design an informative sample assessment strategy for screening informative unlabeled data. An observer network is introduced to confirm the confidence of segmented voxels based on the inconsistency to a backbone segmentation network. To further improve the efficiency of the sample screening, a maximum-connected probability map (MCP-Map) is introduced to eliminate the influence of outliers in the result of coarse segmentation. Experimental results show that our methods have the highest labeling efficiency and the lowest labeling cost compared with several existing active learning methods. With 40% labeled reduce, our method achieved 95.67% in Dice Similarity Coefficient (DSC), which is the state-of-the-art in the labyrinth segmentation.