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Truly Concomitant and Independently Expressed Short- and Long-Term Plasticity in a Bi <sub/>2</sub> O <sub/>2</sub> Se-Based Three-Terminal Memristor
摘要： Concomitance of diverse synaptic plasticity across different timescales produces complex cognitive processes. To achieve comparable cognitive complexity in memristive neuromorphic systems, devices that are capable of emulating short-term (STP) and long-term plasticity (LTP) concomitantly are essential. In existing memristors, however, STP and LTP can only be induced selectively because of the inability to be decoupled using different loci and mechanisms. In this work, the first demonstration of truly concomitant STP and LTP is reported in a three-terminal memristor that uses independent physical phenomena to represent each form of plasticity. The emerging layered material Bi2O2Se is used for memristors for the first time, opening up the prospects for ultrathin, high-speed, and low-power neuromorphic devices. The concerted action of STP and LTP allows full-range modulation of the transient synaptic efficacy, from depression to facilitation, by stimulus frequency or intensity, providing a versatile device platform for neuromorphic function implementation. A heuristic recurrent neural circuitry model is developed to simulate the intricate “sleep–wake cycle autoregulation” process, in which the concomitance of STP and LTP is posited as a key factor in enabling this neural homeostasis. This work sheds new light on the development of generic memristor platforms for highly dynamic neuromorphic computing.
关键词： Bi2O2Se,hybrid density functional calculations,long-term plasticity,short-term plasticity,three-terminal memristors
更新于2025-09-23 15:21:01
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Thickness-modulated in-plane Bi<sub>2</sub>O<sub>2</sub>Se homojunctions for ultrafast high-performance photodetectors
摘要： Bi2O2Se thin film could be one of the promising material candidates for next-generation electronic and optoelectronic applications with the outstanding electrical and optoelectrical properties. However, the device performance based on the Bi2O2Se thin films was not fully explored in the photodetecting area. Considering that the electrical properties such as carrier mobility, work function and energy band structure of Bi2O2Se are thickness dependent, in-plane Bi2O2Se homojunctions consisting of layers with different thickness were successfully synthesized by CVD method across the terraces on the mica substrates, where terraces were created during the mica surface layer peeling off process. In this way, effective internal electrical fields were built up along the Bi2O2Se homojunctions, The Bi2O2Se in-plane homojunctions exhibiting diode-like rectification behavior with an on/off ratio of 102, what’s more, the photodetectors based on which were featured as highly sensitive and ultrafast with the maximum photoresponsivity of 2.5A/W and the lifetime of 4.8μs. Compared with the Bi2O2Se uniform thin films, the photo-electric conversion efficiency was greatly improved for the in-plane homojunctions.
关键词： thickness modulation,in-plane homojunction,photodetectors,Bi2O2Se
更新于2025-09-23 15:19:57
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Two-Dimensional Bi <sub/>2</sub> O <sub/>2</sub> Se with High Mobility for High-Performance Polymer Solar Cells
摘要： Carrier mobility is a critical factor for power conversion efficiency (PCE) of polymer solar cells (PSCs), and the low charge carrier mobility still limits performance improvement of PSCs. Adding high mobility material into the active layer is one of the better ways to enhance the PCE of PSCs. Two-dimensional (2D) Bi2O2Se can be an ideal additive material for improving the carrier mobility of PSCs because its ultrahigh mobility and high thermal stability. In this work, the Bi2O2Se few-layer 2D nanoflakes are fabricated by combining lithium intercalation with shear force-assisted liquid phase exfoliation and applied as an additive to promote charge transport in PSCs for the first time. The 2D Bi2O2Se nanoflakes, when introduced into the active layer, not only provide new interface between donor and acceptor and efficient charge transfer pathways but also induce crystallization of photosensitive layer and form the continuous interpenetrating networks, which promotes the exciton separation and charge transfer in photosensitive layer. As a result, the PCE of device based on PBDB-T:ITIC is increased from 10.09% (0 wt%) to 12.22% (2 wt%). Meanwhile, the PCE of device based on PM6:Y6 is also increased from 14.59% for binary device to 16.28% for optimized ternary device (2 wt%). Moreover, the optimized ternary device shows excellent air stability by suppressing the mixing of the two phases. This work supplies a good method to enhance the PCE of PSCs, also shows the Bi2O2Se material has a good prospect in photovoltaic devices.
关键词： crystallinity,charge recombination,Polymer solar cells,stability,carrier mobility,2D Bi2O2Se flakes
更新于2025-09-19 17:13:59
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Bolometric Effect in Bi <sub/>2</sub> O <sub/>2</sub> Se Photodetectors
摘要： Bi2O2Se is emerging as a photosensitive functional material for optoelectronics, and its photodetection mechanism is mostly considered to be a photo-conductive regime in previous reports. Here, the bolometric effect is discovered in Bi2O2Se photodetectors. The coexistence of photoconductive effect and bolometric effect is generally observed in multiwavelength photoresponse measurements and then confirmed with microscale local heating experiments. The unique photoresponse of Bi2O2Se photodetectors may arise from a change of hot electrons during temperature rises instead of photoexcited holes and electrons. Direct proof of the bolometric effect is achieved by real-time temperature tracking of Bi2O2Se photodetectors under time evolution after light excitation. Moreover, the Bi2O2Se bolometer shows a high temperature coefficient of resistance (?1.6% K?1), high bolometric coefficient (?31 nA K?1), and high bolometric responsivity (>320 A W?1). These findings offer a new approach to develop bolometric photodetectors based on Bi2O2Se layered materials.
关键词： bolometric effect,photodetectors,Bi2O2Se
更新于2025-09-19 17:13:59
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Highly efficient broadband photodetectors based on lithography-free Au/Bi <sub/>2</sub> O <sub/>2</sub> Se/Au heterostructures
摘要： As one of the bismuth-based oxychalcogenide materials, Bi2O2Se ultrathin films have received intense research interest due to their high carrier mobility, narrow bandgaps, ultrafast intrinsic photoresponse and long-term ambient stability; they exhibit great potential in electronic and optoelectronic applications. However, the device performance of photodetectors based on metal/Bi2O2Se/metal structures has degraded due to the undesirable defects or contaminants from the electrode deposition or the sample transfer processes. In this work, highly efficient photodetectors based on Au/Bi2O2Se junctions were achieved with Au electrodes transferred under the assistance of a probe tip to avoid contaminants from traditional lithography methods. Furthermore, to improve the charge transfer efficiency, specifically by increasing the intensity of the electrical field at the Au/Bi2O2Se interface and along the Bi2O2Se channels, the device annealing temperature was optimized to narrow the van der Waals gap at the Au/Bi2O2Se interface and the device channel length was shortened to improve the overall device performance. Among all the devices, the maximum device photoresponsivity was 9.1 A W?1, and the device response time could approach 36 μs; moreover, the photodetectors featured broadband spectral responses from 360 nm to 1090 nm.
关键词： photodetectors,Au/Bi2O2Se/Au heterostructures,Bi2O2Se,broadband spectral responses
更新于2025-09-16 10:30:52
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Epitaxial growth and characterization of high quality Bi<sub>2</sub>O<sub>2</sub>Se thin films on SrTiO<sub>3</sub> substrates by pulsed laser deposition
摘要： Recently, Bi2O2Se is discovered as a promising two-dimensional (2D) semiconductor for next generation electronics, due to its moderate bandgap size, high electron mobility and pronounced ambient stability. Meanwhile, it has been predicted that high quality Bi2O2Se-related heterostructures may possess exotic physical phenomena, such as piezoelectricity and topological superconductivity. Herein, we report the first successful heteroepitaxial growth of Bi2O2Se films on SrTiO3 substrates via pulsed laser deposition (PLD) method. Films obtained under optimal conditions show an epitaxial growth with the c axis perpendicular to the film surface and the a and b axes parallel to the substrate. The growth mode transition to three dimensional (3D) island is observed as prolonging deposition time of films. The maximum value of electron mobility reaches 160 cm2/V-1s-1 at room temperature in a 70 nm-thick film. The thickness dependent mobility provides evidence that interface-scattering is likely to be the limiting factor for the relatively low electron mobility at low temperature, implying that the interface engineering as an effective method to tune the low temperature electron mobility. Our work suggests the epitaxial Bi2O2Se films grown by PLD are promising for both fundamental study and practical applications.
关键词： Bi2O2Se,pulsed laser deposition,heterostructure,high mobility,two-dimensional materials
更新于2025-09-16 10:30:52
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Biodegradable Bi <sub/>2</sub> O <sub/>2</sub> Se Quantum Dots for Photoacoustic Imaging-Guided Cancer Photothermal Therapy
摘要： As new 2D layered nanomaterials, Bi2O2Se nanoplates have unique semiconducting properties that can benefit biomedical applications. Herein, a facile top-down approach for the synthesis of Bi2O2Se quantum dots (QDs) in a solution is described. The Bi2O2Se QDs with a size of 3.8 nm and thickness of 1.9 nm exhibit a high photothermal conversion coefficient of 35.7% and good photothermal stability. In vitro and in vivo assessments demonstrate that the Bi2O2Se QDs possess excellent photoacoustic (PA) performance and photothermal therapy (PTT) efficiency. After systemic administration, the Bi2O2Se QDs accumulate passively in tumors enabling efficient PA imaging of the entire tumors to facilitate imaging-guided PTT without obvious toxicity. Furthermore, the Bi2O2Se QDs which exhibit degradability in aqueous media not only have sufficient stability during in vivo circulation to perform the designed therapeutic functions, but also can be discharged harmlessly from the body afterward. The results reveal the great potential of Bi2O2Se QDs as a biodegradable multifunctional agent in medical applications.
关键词： biodegradable,Bi2O2Se,2D layered materials,photothermal agents,photoacoustic imaging
更新于2025-09-11 14:15:04
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Electron and phonon transport properties of layered Bi <sub/>2</sub> O <sub/>2</sub> Se and Bi <sub/>2</sub> O <sub/>2</sub> Te from first-principles calculations
摘要： Recent experiments indicated that both layered Bi2O2Se and Bi2O2Te are promising thermoelectric materials with low thermal conductivities. However, theoretical study on the thermoelectric properties, especially the phonon transport properties, is rare. In order to understand the thermoelectric transport mechanism, we here investigate the electron and phonon transport properties by using the first-principles calculations combined with the Boltzmann transport theory. Our results indicate that both Bi2O2Se and Bi2O2Te are semiconductors with indirect energy gaps of 0.87 eV and 0.21 eV within spin–orbit coupling, respectively. Large Seebeck coefficient and power factor are found in the p-type than the n-type for both compounds. Low lattice thermal conductivities at room temperature are obtained, 1.14 W m?1 K?1 for Bi2O2Se and 0.58 W m?1 K?1 for Bi2O2Te, which are close to the experimental values. It is found that the low-frequency optical phonon branches with higher group velocity and longer lifetime also make a main contribution to the lattice thermal conductivity. Interestingly, the lattice thermal conductivity exhibits obvious anisotropy especially for Bi2O2Te. These results are helpful for the understanding and optimization of thermoelectric performance of layered Bi2O2Se and Bi2O2Te.
关键词： thermoelectric,Bi2O2Se,lattice thermal conductivity,Bi2O2Te,first-principles
更新于2025-09-04 15:30:14