Publisher：Advanced Functional Materials  

2D Ruddlesden─Popper (RP) halide perovskites are attracting increasing research interest due to their enhanced stability compared to 3D perovskites. However, the quantum confinement effect of bulk organic spacers hinders the separation and transport of photo-generated carriers. Here, a multiple aromatic ring spacer, 3-benzothiophene methylammonium (BTMA), is developed for a new 2D RP perovskite. The BTMA spacer is demonstrated, with a significant dipole moment, can impair the influence of the quantum confinement effect, and the presence of S atoms or thiophene is favorable for enhancing the interaction between organic spacers and inorganic sheets, improving the stability of perovskites. The perovskite photodetector with BTMA as spacers displays higher device performance than the control sample with 1-naphthalene methylammonium (NMA) as spacers. Importantly, the outstanding stability of BTMA-based perovskite films and devices is also confirmed under moisture, heat, and illumination conditions. Combining the asymmetric coplanar nanogap electrode architecture, the photodetectors' enhanced responsivity, detectivity, and external quantum efficiency of 314 A W−1, 3.4 × 1013 Jones, and 865%, respectively, are demonstrated. Importantly, the nanogap photodetectors display promising self-power characteristics, which makes them attractive for numerous energy-efficient applications. The work highlights a new route toward developing high-performance 2D RP perovskite-based photodetectors with excellent long-term stability.

DOI： 10.1002/adfm.202403746

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Language：English   Publisher：Small  

As demand for higher integration density and smaller devices grows, silicon-based complementary metal-oxide-semiconductor (CMOS) devices will soon reach their ultimate limits. 2D transition metal dichalcogenides (TMDs) semiconductors, known for excellent electrical performance and stable atomic structure, are seen as promising materials for future integrated circuits. However, controlled and reliable doping of 2D TMDs, a key step for creating homogeneous CMOS logic components, remains a challenge. In this study, a continuous electrical polarity modulation of monolayer WS2 from intrinsic n-type to ambipolar, then to p-type, and ultimately to a quasi-metallic state is achieved simply by introducing controllable amounts of vanadium (V) atoms into the WS2 lattice as p-type dopants during chemical vapor deposition (CVD). The achievement of purely p-type field-effect transistors (FETs) is particularly noteworthy based on the 4.7 at% V-doped monolayer WS2, demonstrating a remarkable on/off current ratio of 105. Expanding on this triumph, the first initial prototype of ultrathin homogeneous CMOS inverters based on monolayer WS2 is being constructed. These outcomes validate the feasibility of constructing homogeneous CMOS devices through the atomic doping process of 2D materials, marking a significant milestone for the future development of integrated circuits.

DOI： 10.1002/smll.202402217

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PubMed

Publisher：Matter  

van der Waals (vdWs) dielectrics are widely used in nanoelectronics to preserve the intrinsic properties of two-dimensional (2D) semiconductors. However, achieving aligned growth of 2D semiconductors and their direct utilization on original vdWs epitaxial dielectrics to avoid disorders poses significant challenges. Here, a hydromechanical strategy for aligned epitaxy of 2D materials on naturally occurring vdWs mica dielectrics is developed. By combining density functional theory with Lagrange's group theorem, a quantitative criterion for 2D material epitaxy on 6-fold symmetric vdWs dielectrics is established. Moreover, the as-grown ultrathin Bi2O2Se-channeled field-effect transistor, with a hybrid dielectric layer, achieves a superior current on/off ratio (1.4 × 107) and high carrier mobility (22.4 cm2 V−1 S−1) by directly integrating as-grown 2D materials/vdWs dielectrics. This work provides a powerful methodological platform for aligned 2D material synthesis, alignment direction prediction, and intrinsic property investigation, laying the foundation for advanced electronics on as-grown 2D materials/vdWs dielectrics.

DOI： 10.1016/j.matt.2024.04.013

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Publisher：Advanced Optical Materials  

Van der Waals (vdW) heterostructures have gained significant attention in photodetectors due to their seamless integration with materials possessing diverse functionalities. In this study, the fabrication of a Te nanomesh/black-Si vdW heterostructure is presented, and investigated its photoresponse properties. The heterostructure exhibits a pronounced rectification behavior, characterized by a rectification ratio of 2.2 × 104. Notably, the heterostructure device demonstrates commendable photoresponse properties, including a high responsivity of 350 mA W−1, an extensive linear dynamic range of 45.5 dB, a high specific detectivity of 9.6 × 1011 Jones, and a wide spectral response ranging from 400 to 1550 nm. Furthermore, the heterostructure exhibits rapid response, with a rise time and a decay time of 70 and 140 µs, respectively. These exceptional photoresponse properties can be attributed to the robust internal built-in electrical field at the hetero-interface and the augmented light absorption in black-Si. The outstanding photoresponse properties of the heterostructure make it a promising candidate for multiwavelength single-pixel imaging, enabling the collection of mask patterns under varying wavelengths of light radiation. This work provides a novel approach for fabricating mixed-dimensional vdW heterostructures, offering promising prospects for advancements in optoelectronics.

DOI： 10.1002/adom.202400056

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Publisher：Materials Today Electronics  

Perovskites have emerged as a promising new generation of photovoltaic conversion materials, gradually surpassing traditional silicon-based materials in solar cell research. This development is primarily due to their superior power-conversion efficiency (PCE), simple fabrication process, and cost-effective production. However, the low stability of perovskite ionic crystals poses a significant challenge to their stability, hindering the progress of perovskite materials and devices. Although two-dimensional (2D) perovskites offer improved stability, adding organic amine ions results in a quantum confinement effect that reduces the optoelectronic performance of devices. To counter this issue, the strategic design of suitable spacer cations offers a potential solution. Aromatic amine ions possess greater polarity and structural adjustability compared to aliphatic amine ions, making them advantageous in mitigating the quantum confinement effect. This review focuses on phenylethylammonium (PEA) as a representative aromatic spacer cation. It categorizes the evolution of these cations into four trajectories: alkyl chain modification, substitution of hydrogen atoms on the aromatic ring with specific substituents, replacement of benzene rings with aromatic heterocycles, and utilization of multiple aromatic rings instead of a monoaromatic ring. The structure, properties, and corresponding device performance of aromatic spacer cations utilized in reported 2D perovskites are discussed, followed by the presentation of a series of factors for selecting and designing aromatic amine ions for future development.

DOI： 10.1016/j.mtelec.2024.100100

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Language：English   Publisher：Nature Communications  

Inorganic semiconductors typically have limited p-type behavior due to the scarcity of holes and the localized valence band maximum, hindering the progress of complementary devices and circuits. In this work, we propose an inorganic blending strategy to activate the hole-transporting character in an inorganic semiconductor compound, namely tellurium-selenium-oxygen (TeSeO). By rationally combining intrinsic p-type semimetal, semiconductor, and wide-bandgap semiconductor into a single compound, the TeSeO system displays tunable bandgaps ranging from 0.7 to 2.2 eV. Wafer-scale ultrathin TeSeO films, which can be deposited at room temperature, display high hole field-effect mobility of 48.5 cm2/(Vs) and robust hole transport properties, facilitated by Te-Te (Se) portions and O-Te-O portions, respectively. The nanosphere lithography process is employed to create nanopatterned honeycomb TeSeO broadband photodetectors, demonstrating a high responsibility of 603 A/W, an ultrafast response of 5 μs, and superior mechanical flexibility. The p-type TeSeO system is highly adaptable, scalable, and reliable, which can address emerging technological needs that current semiconductor solutions may not fulfill.

DOI： 10.1038/s41467-024-48628-z

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Publisher：Applied Physics Reviews  

The Von Neumann architecture has been the foundation of modern computing systems. Still, its limitations in processing large amounts of data and parallel processing have become more apparent as computing requirements increase. Neuromorphic computing, inspired by the architecture of the human brain, has emerged as a promising solution for developing next-generation computing and memory devices with unprecedented computational power and significantly lower energy consumption. In particular, the development of optoelectronic artificial synaptic devices has made significant progress toward emulating the functionality of biological synapses in the brain. Among them, the potential to mimic the function of the biological eye also paves the way for advancements in robot vision and artificial intelligence. This review focuses on the emerging field of optoelectronic artificial synapses and memristors based on low-dimensional nanomaterials. The unique photoelectric properties of these materials make them ideal for use in neuromorphic and optoelectronic storage devices, with advantages including high carrier mobility, size-tunable optical properties, and low resistor-capacitor circuit delay. The working mechanisms, device structure designs, and applications of these devices are also summarized to achieve truly sense-storage-computer integrated optoelectronic artificial synapses.

DOI： 10.1063/5.0173547

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Publisher：Journal of Materiomics  

Organic-inorganic halide perovskite, as a low-cost, solution-processable material with remarkable optoelectronic properties, is ideal candidate to fabricate high-performance photodetectors and is expected to significantly reduce device costs. Compared to the common Dion-Jacobson and Ruddlesden-Popper two-dimensional (2D) layered hybrid perovskite compounds, the perovskites with alternating cations in the interlayer (ACI) phase show higher crystal symmetry and narrower optical bandgaps, which exhibit great potential for excellent photodetection performance. Herein, we report a high-performance photodetector based on the 2D bilayered hybrid lead halide perovskite single crystal with the ACI phase (GAMA2Pb2I7; GA = C(NH2)3 and MA = CH3NH3). The single-crystal photodetector exhibits high photoresponsivity of 1.56, 2.54, and 2.60 A/W for incident light wavelengths of 405, 532, and 635 nm under 9.82 nW, respectively, together with the correspondingly high detectivity values of 1.86 × 1012, 3.04 × 1012, and 3.11 × 1012 Jones under the same operating conditions. Meanwhile, a high-resolution imaging sensor is built based on the GAMA2Pb2I7 single-crystal photodetector, confirming the high stability and photosensitivity of the imaging system. These results show that the 2D hybrid lead halide perovskites with alternating interlayer cations are promising for high-performance visible light photodetectors and imaging systems.

DOI： 10.1016/j.jmat.2023.05.003

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Language：English  

Halide perovskites have attracted significant recent attention due to their remarkable photoelectric properties; however, the poor structural and moisture stability limit their use for practical utilization. Interestingly, binary halides, such as BiI3 and PbI2, are the typical constituents of halide perovskites, where they do not only have the similar outstanding properties of perovskites but also the superior stability. Herein, the synthesis of layered BiI3 and PbI2 microcrystals by simple drop-casting is investigated and their enhanced photoelectric performance compared to the thin-film counterparts obtained by conventional spin-coating is demonstrated. For the formation of high-quality layered microcrystals, the keys are adopting glycol as a green solvent and appropriate temperature during processing. Once configured into photodetectors, the BiI3 and PbI2 microcrystals exhibit a higher photocurrent, on/off current ratio, responsivity, and other performance parameters than their thin-film devices. These improved performances of microcrystals can be attributed to their superior crystallinity, thanks to the excellent solvent properties of glycol and the optimal growth temperature chosen. This work proposes a more simple and effective solution processing technique to fabricate layered binary halides with higher quality than the conventional spin-coating method, enabling the further development of halides-based optoelectronic devices.

CiNii Research

Publisher：Nano Research  

Due to the exciting photoelectric properties, better stability, and environmental-friendly nature, all-inorganic halide perovskites (AIHPs), especially the lead-free perovskites, have attracted worldwide attention. However, the film quality of AIHPs fabricated by typical spin-coating and subsequent high-temperature annealing is still not satisfactory, restricting their further development. Herein, we demonstrate a simple low-temperature solution-processed drop-casting method to achieve highly-crystalline cubic CsPbBr3 and lead-free layer-structured Cs3Sb2I9 microcrystals (MCs). This drop-casting technique not only consumes the less amount of precursor solution but also eliminates the high-temperature annealing as compared with those of spin coating. When these MCs are configured into photodetectors, they exhibit superior device performance, which is in distinct contrast to the one of spin-coated counterparts. Specifically, the responsivity of CsPbBr3 MCs is found to be as large as 8,990 mA/W, being 13 times larger than the spin-coated films and even better than many state-of-the-art solution-processed AIHPs devices. This device performance enhancement is attributed to the better film quality and phase purity obtained by the drop-casting method. All these results can evidently fill the “technology gap” for further enhancing the material quality of solution-processed AIHPs and breaking down the barriers that hinder the development of AIHPs based optoelectronic devices. [Figure not available: see fulltext.]

DOI： 10.1007/s12274-021-3907-9

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Publisher：APL Materials  

CsPb2Br5/CsPbBr3 composite systems have received considerable attention among numerous lead halide perovskite materials due to their significantly enhanced photoluminescence intensity and stability against moisture. However, the luminescence mechanism of CsPb2Br5 based materials remains controversial, which significantly hinders the further material design and utilization for optoelectronic devices. In this work, to deconvolute their luminescent mechanisms, high-quality CsPb2Br5 crystals without any undesired by-products and impurities have been first prepared by a microwave-assisted synthesis method. The luminescence-inactive characteristics of the material are then confirmed by the steady-state absorption, photoluminescence, transient absorption spectra, and time-resolved terahertz spectroscopy. The prepared CsPb2Br5 crystals exhibit excellent crystallinity and enhanced thermal stability, particularly that they can maintain their crystalline structures in polar organic solvents. By simply manipulating the ratios of different precursor materials, it is witnessed that the green emission comes from the CsPbBr3 adhered, nucleated, and grown on the CsPb2Br5 crystals. Ultrafast transient absorption measurements in visible and terahertz spectral regions reveal that with the help of phonon scattering-assisted hopping at interfacial states, intersystem crossing dominates the electron transfer process in the composite crystals. As a result, the CsPb2Br5 and CsPbBr3 interact extensively with each other. Meanwhile, the Auger recombination rate and the defect-related non-radiative process are suppressed in the composite crystals, thereby enhancing the fluorescence of composite crystals. This work has not only deconvoluted the controversial and unclear luminescent mechanisms of CsPb2Br5 materials but also established a pathway to design and enhance the fluorescence of materials for technological applications.

DOI： 10.1063/5.0083022

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