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Two-Dimensional Fluorine Distribution in a Heavily Distorted Perovskite Nickel Oxyfluoride Revealed by First-Principles Calculation
摘要： Most perovskite oxyfluorides synthesized to date have cubic structures, wherein fluorine atoms tend to reside at every oxygen site randomly. In this theoretical study, we show a two-dimensional fluorine arrangement in a perovskite nickel oxyfluoride (NdNiO2F) with a large orthorhombic distortion. The site selectivity in the perovskite lattice is due to the orthorhombicity, which stabilizes the two-dimensional cis configurations with shorter Ni?O and longer Ni?F bonds to minimize the electrostatic energy. The electronic structure of NdNiO2F is characterized by its large octahedral rotation and the higher electronegativity of fluorine than oxygen. We also observed how the anion arrangement was affected by the biaxial strain by modeling epitaxial strained thin film on substrate and found that the 2D cis structure remains the most stable. However, the orientation of the two-dimensional structure containing F depends on the magnitude of the biaxial strain. Our findings suggest that fluorine doping in orthorhombic perovskite oxides effectively yields oxyfluorides with anisotropic anion ordering.
关键词： electronic structure,orthorhombic distortion,perovskite oxyfluorides,two-dimensional fluorine arrangement,biaxial strain
更新于2025-09-12 10:27:22
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Two-Dimensional Fluorescent Strategy Based on Porous Silicon Quantum Dots for Metal-Ion Detection and Recognition
摘要： A two-dimensional photoluminescent (2D PL) detection strategy was established based on luminescent porous silicon (LuPSi) with wide-size-distributed silicon quantum dots and abundant surface chemistry. Owing to the intrinsic nature of LuPSi, interaction or reaction between analytes and LuPSi may cause static, dynamic, oxidation-induced, and deposition-induced quenching. By monitoring of both the PL intensity change and peak shift of LuPSi, the 2D PL detection strategy could discriminate di?erent analytes. Detection and recognition of di?erent metal ions in real water samples using a single peak were realized. Compared with the existing array-based methods, the 2D PL approach signi?cantly simpli?ed the sensing element and detection process.
关键词： metal ions,quantum dot array,two-dimensional photoluminescence,luminescent porous silicon,recognition
更新于2025-09-12 10:27:22
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Polarization induced two-dimensional electron gas in ZnO/ZnMgO Heterointerface for High-performance enhanced UV photodetector
摘要： The spontaneous formation of two-dimensional electron gas (2DEG) with a high carrier density (~1018 cm-3) was achieved at a ZnO/Mg0.2Zn0.8O interface grown using a facile radio-frequency magnetron sputtering system on a quartz substrate. Compared with Mg0.2Zn0.8O ultraviolet (UV) photodetectors (PDs) with and without a ZnO buffer layer, the PD based on ZnO/Mg0.2Zn0.8O bilayer films exhibited not only sensitivity to dual wavelength in the UV region, but also significantly enhanced spectral responsivity, photocurrent-to-dark current ratio (107), specific detectivity (1014), and UV/visible rejection ratio of about four orders of magnitude at a low operating voltage bias. Induced by 2DEG, the external quantum efficiency (EQE) of photodetector reached 14858% at 10 V, indicating that a considered high gain was achieved in the device based on this heterojunction architecture. The gain mechanism was further demonstrated by polarization induction and band bending in detail. This application of 2DEG in a practical detector offers a novel and effective approach for the substantial improvement in the high-performance of ZnO/Mg0.2Zn0.8O dual-band UV PDs.
关键词： two-dimensional electron gas,polarization,high-performance UV PDs,ZnO/Mg0.2Zn0.8O heterointerface,gain
更新于2025-09-12 10:27:22
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Controlled Plasma Thinning of Bulk MoS <sub/>2</sub> Flakes for Photodetector Fabrication
摘要： The electronic properties of layered materials are directly determined based on their thicknesses. Remarkable progress has been carried out on synthesis of wafer-scale atomically molybdenum disulfide (MoS2) layers as a two-dimensional material in the past few years in order to transform them into commercial products. Although chemical/mechanical exfoliation techniques are used to obtain a high-quality monolayer of MoS2, the lack of suitable control in the thickness and the lateral size of the flakes restrict their benefits. As a result, a straightforward, effective, and reliable approach is widely demanded to achieve a flake with control in its thickness for optoelectronic applications. In this study, thick MoS2 flakes are obtained by a short-time bath sonication in dimethylformamide solvent, which are thinned with the aid of a sequential plasma etching process using H2, O2, and SF6 plasma. A comprehensive study has been carried out on MoS2 flakes based on scanning electron microscopy, atomic force microscopy, Raman, transmission electron microscopy, and X-ray photoelectron microscopy measurements, which ultimately leads to a two-cycle plasma thinning method. In this approach, H2 is used in the passivation step in the first subcycle, and O2/SF6 plasma acts as an etching step for removing the MoS2 layers in the second subcycle. Finally, we show that this technique can be enthusiastically used to fabricate MoS2-based photodetectors with a considerable photoresponsivity of 1.39 A/W and a response time of 0.45 s under laser excitation of 532 nm.
关键词： photodetector,MoS2,optoelectronic applications,plasma thinning,two-dimensional materials
更新于2025-09-12 10:27:22
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Spectral responsivity and photoconductive gain in thin film black phosphorus photodetectors
摘要： We have fabricated black phosphorus photodetectors and characterized their full spectral responsivity. These devices, which are effectively in the bulk thin film limit, show broadband responsivity ranging from <400 nm to the ~3.8 μm bandgap. In the visible, an intrinsic responsivity >6 A/W can be obtained due to internal gain mechanisms. By examining the full spectral response, we identify a sharp contrast between the visible and infrared behavior. In particular, the visible responsivity shows a large photoconductive gain and gate-voltge dependence, while the infrared responsivity is nearly independent of gate voltage and incident light intensity under most conditions. This is attributed to a contribution from the surface oxide. In addition, we find that the polarization anisotropy in responsivity along armchair and zigzag directions can be as large as 103 and extends from the band edge to 500 nm. The devices were fabricated in an inert atmosphere and encapsulated by Al2O3 providing stable operation for more than 6 months.
关键词： Two-dimensional materials,Mid-infrared,Photodetectors,Black phosphorus,Photoconductive gain
更新于2025-09-12 10:27:22
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4-Aminoethyl Pyridine as a Bifunctional Spacer Cation for Efficient and Stable 2D Ruddlesden-Popper Perovskite Solar Cells
摘要： Two-dimensional (2D) Ruddlesden?Popper (RP) perovskites are attractive due to their appealing environmental stability. We demonstrate herein a spacer cation, 4-aminoethyl pyridine (4-AEP), for preparation of 2D RP perovskite films. The 4-AEP can not only act as a spacer cation, but also coordinate with the Pb2+ ions in PbI2 with the nitrogen atom on the pyridine ring. High-quality 2D RP perovskite films can thus be formed as the coordination interaction retards the crystallization rate of the 2D RP perovskites. As a result, the solar cell employing the (4-AEP)2MAn?1PbnI3n+1 (n=5) 2D perovskite achieves a power conversion efficiency (PCE) of 11.68% with good air stability, which is much better than the phenylethylamine spacer cation at the same conditions (PCE = 7.95%). This work provides a new idea for designing novel spacer cations towards efficient and stable 2D RP perovskite solar cells.
关键词： Two-dimensional perovskite,pyridine,spacer cation,perovskite solar cells,crystallization regulation
更新于2025-09-12 10:27:22
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Exploiting Bulk Photovoltaic Effect in a 2D Trilayered Hybrid Ferroelectric for Highly Sensitive Polarized Light Detection
摘要： Polarized light detection is attracting increasing attention for its wide applications ranging from optical switches to high-resolution photodetectors. Two-dimensional (2D) hybrid perovskite-type ferroelectrics combining inherent light polarization dependence of bulk photovoltaic effect (BPVE) with their excellent semiconducting performances present significant potential in this portfolio. Here, we first report the BPVE-driven highly sensitive polarized light detection in a 2D trilayered hybrid perovskite ferroelectric, (allyammonium)2(ethylammonium)2Pb3Br10 (1), which shows superior BPVE with a near-bandgap photovoltage of ~ 2.5 V and a high on/off switching ratio of current (~ 104). Notably, driven by the superior BPVE, 1 exhibits highly sensitive polarized light detection with a polarization ratio as high as ~15, which is far more beyond than those of structural anisotropy-based monocomponent devices. As far as we know, this is the first realization of BPVE-driven polarized light detection in hybrid perovskite ferroelectrics. This work opens a new avenue for the design of highly sensitive polarized light detection by exploiting the sinusoidal behavior of BPVE current in 2D multilayered hybrid perovskite ferroelectrics.
关键词： Ferroelectric photovoltaic,Two-dimensional hybrid perovskite,Polarization-sensitive photodetection,Bulk photovoltaic effect,Ferroelectric material
更新于2025-09-12 10:27:22
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Orientation-Controlled 2D Anisotropic and Isotropic Photon Transport in Cocrystal Polymorph Microplates
摘要： Two-dimensional (2D) anisotropic transport of photons/electrons is crucial for constructing ultracompact on-chip circuits. To date, the photons in organic 2D crystals usually exhibit the isotropic propagation, and the anisotropic behaviors have not yet been fully demonstrated. Herein, an orientation-controlled photon-dipole interaction strategy was proposed to rationally realize the anisotropic and isotropic 2D photon transmissions in two self-assembled cocrystal polymorph microplates. The monoclinic microplate adopting a nearly horizontal molecular transition dipole orientation in the 2D plane, exhibits anisotropic photon-dipole interactions and thus distinct re-absorption waveguide losses for different 2D directions. By contrast, the triclinic microplate with a vertical transition dipole orientation, shows the 2D isotropic photon-dipole interactions and thus the same re-absorption losses along different directions. Based on the anisotropic transport mechanism, a directional signal outcoupler (DSO) was further designed for the high-fidelity transmission of the real signals, which would enlighten the development of 2D anisotropic optical devices.
关键词： two-dimensional photonics,anisotropic optical waveguides,Cocrystal,polymorphs,transition dipole moment
更新于2025-09-12 10:27:22
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Exploiting Bulk Photovoltaic Effect in a 2D Trilayered Hybrid Ferroelectric for Highly Sensitive Polarized Light Detection
摘要： Polarized light detection is attracting increasing attention for its wide applications ranging from optical switches to high-resolution photodetectors. Two-dimensional (2D) hybrid perovskite-type ferroelectrics combining inherent light polarization dependence of bulk photovoltaic effect (BPVE) with their excellent semiconducting performances present significant potential in this portfolio. Here, we first report the BPVE-driven highly sensitive polarized light detection in a 2D trilayered hybrid perovskite ferroelectric, (allyammonium)2(ethylammonium)2Pb3Br10 (1), which shows superior BPVE with a near-bandgap photovoltage of ~ 2.5 V and a high on/off switching ratio of current (~ 104). Notably, driven by the superior BPVE, 1 exhibits highly sensitive polarized light detection with a polarization ratio as high as ~15, which is far more beyond than those of structural anisotropy-based monocomponent devices. As far as we know, this is the first realization of BPVE-driven polarized light detection in hybrid perovskite ferroelectrics. This work opens a new avenue for the design of highly sensitive polarized light detection by exploiting the sinusoidal behavior of BPVE current in 2D multilayered hybrid perovskite ferroelectrics.
关键词： Ferroelectric photovoltaic,Two-dimensional hybrid perovskite,Polarization-sensitive photodetection,Bulk photovoltaic effect,Ferroelectric material
更新于2025-09-12 10:27:22
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Efficient Quasi-Two-Dimensional Perovskite Light-Emitting Diodes with Improved Multiple Quantum Well Structure
摘要： Quasi-two-dimensional (quasi-2D) perovskites with a multiple quantum well structure can enhance the exciton binding energy and controllable quantum con?ne e?ect, which are attractive materials for e?cient perovskite light-emitting diodes (PeLEDs). However, the multiphase mixtures contained in these materials would cause nonradiative recombination at the perovskite ?lm surface. Here, a facile solution surface treatment is adopted to improve the multiple quantum well structure of the quasi-2D perovskite emitting layer, which can reduce the in?uence of defectinduced nonradiative recombination and the electric-?eld-induced dissociation of excitons for the PeLEDs. The improved multiple quantum well structure is veri?ed by UV absorption spectra and temperature-dependent photoluminescence spectra measurements. The photoluminescence quantum yield of the quasi-2D perovskite ?lm with surface treatment has been approximately increased by 200%. Meanwhile, the electroluminescence device achieves a current e?ciency of 45.9 cd/A.
关键词： electroluminescence,quasi-two-dimensional perovskite light-emitting diodes,surface treatment,multiple quantum well structure,photoluminescence quantum yield
更新于2025-09-12 10:27:22