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- 摘要
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- 实验方案
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Faceta??Dependent, Fast Response, and Broadband Photodetector Based on Highly Stable Alla??Inorganic CsCu <sub/>2</sub> I <sub/>3</sub> Single Crystal with 1D Electronic Structure
摘要： Low-dimensional metal halides at molecular level, which feature strong quantum confinement effects from intrinsic structure, are emerging as ideal candidates in optoelectronic fields. However, developing stable and nontoxic metal halides still remains a great challenge. Herein, for the first time, high-crystalline and highly stable CsCu2I3 single crystal, which is acquired by a low-cost antisolvent vapor assisted method, is successfully developed to construct high-speed (trise/tdecay = 0.19 ms/14.7 ms) and UV-to-visible broadband (300–700 nm) photodetector, outperforming most reported photodetectors based on individual all-inorganic lead-free metal halides. Intriguingly, facet-dependent photoresponse is observed for CsCu2I3 single crystal, whose morphology consists of {010}, {110}, and {021} crystal planes. The on–off ratio of {010} crystal plane is higher than that of {110} crystal plane, mainly owing to lower dark current. Furthermore, photogenerated electrons are localized in twofold chains created by [CuI4] tetrahedra, leading to relatively small effective mass and fast transport mobility along the 1D transport pathway. Anisotropic carrier transport characteristic is related to stronger confinement and higher electron density for {110} crystal planes. This work not only demonstrates the great potential of CsCu2I3 single crystal in high-performance optoelectronics, but also gives insights into 1D electronic structure associated with fast photoresponse and high anisotropy.
关键词： photodetectors,facet-dependent photoresponse,1D electronic structures,highly stable,fast response
更新于2025-09-23 15:21:01
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Electronic Structures of Ge <sub/>2</sub> Sb <sub/>2</sub> Te <sub/>5</sub> /Co <sub/>2</sub> FeX (X: Al, Si) Interfaces for Phase Change Spintronics
摘要： Phase change materials (PCMs), such as Ge2Sb2Te5, are highly attractive in modern electronics and photonics. However, their spintronic applications remain largely unexplored. Here, we propose a tentative modality of phase change spintronic devices based on the ferromagnet/PCM/ferromagnet structure. The electrically tunable properties of a PCM interlayer give rise to new possibilities of manipulating spin transport through phase change, adding new functionalities and modes of operation to the spintronic devices. As the first step toward realizing such phase change spintronic devices, we calculate the electronic structures of the interfaces of c-Ge2Sb2Te5 and half-metallic ferromagnetic Co2FeX (X: Al, Si). The interfaces are found not to be genuine half-metallic, indicating room for improvement. The band alignments are largely determined by the termination of c-Ge2Sb2Te5. Two types of band alignments are found for c-Ge2Sb2Te5/Co2FeX interfaces. Considering c-Ge2Sb2Te5 as heavily p-type-doped, interfaces with Te termination are generally suitable such that they offer low contact resistance for hole injection from Co2FeX to c-Ge2Sb2Te5 in the majority spin channel; at the same time, they naturally form tunneling barriers, alleviating the degradation of spin injection efficiency because of occasional hole injection in the minority spin channel. This work provides important insights into this proposed phase change spintronic framework.
关键词： Spintronics,Electronic structures,Co2FeX,Interface,Phase change materials,Ge2Sb2Te5
更新于2025-09-23 15:21:01
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Vapor-deposited all inorganic CsPbBr3 thin films and interface modification with C8-BTBT for high performance photodetector
摘要： All inorganic perovskites like CsPbBr3 have attracted rising attention and are considered as promising candidates for optoelectronic devices. Here we fabricated CsPbBr3 films by co-evaporation. The as-deposited and low temperature (below 300 °C) annealed films are in a mixture phase of CsPbBr3 and CsPb2Br5. After 400 °C annealing in ambient air, the CsPbBr3 phase becomes dominant with a good crystal structure and less defects. Then, 2,7-diocty[1]benzothieno-[3,2-b]benzothiophen (C8-BTBT) was deposited on the CsPbBr3 film layer-by-layer to investigate the interface electronic structure with X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). As C8-BTBT was deposited, p-doping effect was observed at the surface of CsPbBr3 by the interface energy level alignment. At the same time, we also observed a chemical reaction at the interface and a small amount of lead sulfite might be formed. CsPbBr3 based photodetectors with or without C8-BTBT modified layer were also fabricated and studied. It was found that the photocurrent of the detectors with an additional C8-BTBT layer was about two orders of magnitude higher than that without C8-BTBT layer. The responsivities and response time are also improved with C8-BTBT. We attribute the improvement of photoelectronic properties to the interface energy level adjustment by the C8-BTBT. These results highlight the potential of C8-BTBT as a modified layer for inorganic perovskite optoelectronic devices.
关键词： CsPbBr3 films,C8-BTBT,Interfacial electronic structures,Vacuum evaporation,Photoelectronic properties
更新于2025-09-23 15:21:01
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The electronic structures and optical properties of B, C or N doped BaTiO <sub/>3</sub>
摘要： The electronic structures and optical properties of Boron, Carbon or Nitrogen doped BaTiO3 are calculated by the first-principles calculations. The doped atoms decrease the band gap of BaTiO3 significantly, which could increase the host material ability to absorb the visible light. The absorption spectrum calculations confirm that both Boron and Carbon-doped BaTiO3 have a favorable performance in the absorption of visible light. However, Nitrogen-doped BaTiO3 doesn’t present the improvement. BaTiO3 doped with Boron or Carbon is expected to be a new class of perovskite materials for the field of solar energy.
关键词： BaTiO3,doping,optical properties,solar energy,electronic structures
更新于2025-09-23 15:21:01
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First-principles study on photovoltaic properties of 2D Cs <sub/>2</sub> PbI <sub/>4</sub> -black phosphorus heterojunctions
摘要： Both 2D perovskite Cs2PbI4 and phosphorus are significant optoelectronic semiconductor materials, the optical-electrical characters between both contact interfaces are interesting topics. In present work, we demonstrate comparative investigation of optoelectronic properties for two kinds of electrical contact interfaces. i.e. Pb–I and Cs–I interfaces with black phosphorus contacts. The carrier transport, charge transferring and optical properties for both cases are investigated by using first principle calculation. Both contact interfaces exhibit type II band alignment with direct band gap. Charge carrier migration from Cs–I interface to black phosphorus is more strong than that of Pb–I interface by considering differential charge density and bader charge between distinct electrical contact interfaces. Besides, electron–hole effective masses of heterojunctions for both cases along different direction are investigated. Optical absorption coefficients of both cases are compared with those of free-standing Cs2PbI4 and black phosphorus in the visible spectrum. We systematically compared advantages and disadvantages of two kinds of contact interfaces for photovoltaic application, and the results reveal interfacial engineering of 2D heterojunction plays a important role in tuning optoelectronic properties.
关键词： optical property,first-principles,electronic structures,2D heterojunction,carrier effective masses,charge transfer
更新于2025-09-23 15:19:57
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First-principles calculations on effects of Al and Ga dopants on atomic and electronic structures of amorphous Ge <sub/>2</sub> Sb <sub/>2</sub> Te <sub/>5</sub>
摘要： Effects of post-transition metal dopants M (M = Al, Zn, and Ga) on structural and electronic properties of amorphous Ge2Sb2Te5 (a-GST) are investigated through first-principles calculations based on the density functional theory. The doped a-GST is generated through the melt-quench procedure using molecular dynamics simulations. It is found that the three dopants behave similarly in a-GST, and they are mostly coordinated by Te atoms in tetrahedral geometry, which is similar to those in crystalline MxTey. This is in contrast with crystalline GST wherein the most stable position of dopant M is the octahedral vacancy site. The number of wrong bonds such as Ge–Ge, Ge–Sb, or Sb–Sb increases as dopant atoms predominantly bond with Te atoms. The number of 4-fold ring structures, especially ABAB-type, decreases significantly, explaining the enhanced thermal stability of doped a-GST in the experiment. The bandgap estimated from density of states and the optical gap obtained from Tauc plot increase upon doping, which is also in good agreement with the experiment. By successfully relating the experimental doping effects and changes in the atomic structure, we believe that the present work can serve as a key to offer better retention and lower power consumption in phase-change memory.
关键词： amorphous Ge2Sb2Te5,electronic structures,first-principles calculations,atomic structures,Al and Ga dopants
更新于2025-09-19 17:15:36
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Theoretical Study on Nanostructural Modifications of the Si (111) Surface
摘要： Modified Si(111) surface with designed nanostructural modifications including grown pits, nanobars and nanoislands as well as deposited hill-, diamond- and cage-like nanoclusters were studied using density-functional theory (DFT) calculations. The thermal stabilities, electronic structures and optical properties of these various nanostructural modifications of the Si(111) surface were calculated and discussed. The results indicate that the optical absorption of the modified Si(111) surface can be enhanced by these surface modifications especially when depositing diamond-like nanoclusters on the surface.
关键词： electronic structures,Si(111) surface modifications,Si nanostructures,optical properties
更新于2025-09-19 17:15:36
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Substitutional effect of different bridging groups on optical and charge transfer properties of small bipolar molecules for OLEDs
摘要： In this work, a series of eight different bipolar molecules were designed and calculated using density functional theory (DFT) and time‐dependent functional theory (TD‐DFT) for organic light emitting diodes (OLEDs) as efficient luminescent and charge transfer materials. The eight donor‐π‐donor type small molecules (D1‐D8) were composed of triphenylamine (TPA) donor (D) unit connected to 1,8‐naphthalimides (NI) acceptor (A) unit though different π‐conjugated or R‐groups (as π‐spacer). The effect of substitutions made in π‐spacer was investigated on optical, electronic, and stability properties. This calculation analysis showed that different substitutions in π‐spacer resulted smaller Eg (range from 1.63 to 2.00 eV), broader absorption with the lowest excitation energy covering both visible and near infrared regions of solar spectrum, especially D3, D4, D5, and D6 molecules. The analyses of local densities of states, frontier molecular orbitals, and natural population analysis of orbitals revealed that studied molecules exhibited π‐π* electronic transitions of absorption in singlet excited states, but D5 and D6 also show intramolecular charge transfer (ICT) characteristics. The study of chemical indices, molecular electrostatic potential (MEP) surfaces, and charge transfer properties turned out that D4, D5, and D6 are expected to show good potential for luminescent and hole transport materials in the favor of OLEDs.
关键词： DFT,organic light emitting diodes (OLEDs),optical properties,absorption spectra,electronic structures
更新于2025-09-19 17:13:59
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Fusing Thienyl with N-Annulated Perylene Dyes and Photovoltaic Parameters for Dye-Sensitized Solar Cells
摘要： Due to the role of dye in dye-sensitized solar cells (DSSCs), design novel dye sensitizer is effective strategy to improve power conversion efficiency. To this end, the fundamental issue is the understanding sensitizer’s trilateral relationship among molecular structure, optoelectronic properties and photovoltaic performance. Here, on the one hand, to investigate the relationship between molecular structure and properties, considering the good performance of N-annulated perlyene dye sensitizers, the geometries, electronic structures and excitations of the selected representative organic dye sensitizers C276, C277, C278 and the dyes adsorbed on TiO2 clusters were calculated. It is found that, fusing thienyl to N-annulated perlyene can elevate the highest occupied molecular orbital (HOMO) energies, reduce orbital energy gap, increase density of states, expand HOMO to benzothiadiazole moiety, enhance charge transfer excitation, elongate fluorescence lifetime, amplify light harvesting efficiency and induce red-shift of absorption spectra. The transition configurations and molecular orbitals of dye adsorbed systems support that the electron injection in DSSCs based on these dyes are fast mode. On the other hand, to exposure the relationship between properties and performance, based upon extensive analysis of electronic structures and excitation properties of these dye sensitizers and the dye adsorbed systems, we present new quantities as open-circuit voltage and short-circuit current density descriptors, which celebrate the quantitative bridge between the photovoltaic parameters and the electronic structure related properties. The results of this work are critical for design novel dye sensitizers for solar cells.
关键词： electronic structures,N-annulated perylene dyes,photovoltaic parameters,dye-sensitized solar cells,excitation properties
更新于2025-09-19 17:13:59
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Features of Vibrational and Electronic Structures of Decavanadate Revealed by Resonance Raman Spectroscopy and Density Functional Theory
摘要： Polyoxometalates are known to be inhibitors of a diverse collection of enzymes, although the specific interactions that lead to this bioactivity are still unclear. Spectroscopic characterization may be an invaluable if indirect tool for remedying this problem, yet this requires clear, cogent assignment of polyoxometalate spectra before the complicating effect of their binding to large biomolecules can be considered. We report the use of FT-IR and resonance Raman spectroscopies alongside density functional theory to describe the vibrational and electronic structures of decavanadate, [V10O28]6–. Our computational model, which reproduced the majority of vibrational features to within 10 cm–1, was then used to identify an axial oxo ligand as the most likely position of the acidic proton in the related cluster [HV10O28]5–. As resonance Raman spectroscopy can directly interrogate chromophores embedded in complex systems, this approach may be of general use in answering structural questions about polyoxometalate-enzyme systems.
关键词： vibrational and electronic structures,Polyoxometalates,decavanadate,density functional theory,resonance Raman spectroscopy
更新于2025-09-12 10:27:22