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Thickness dependence of solar cell efficiency in transition metal dichalcogenides MX2 (M: Mo, W; X: S, Se, Te)
摘要： Bulk transition metal dichalcogenides are indirect gap semiconductors with optical gaps in the range of 0.7–1.6 eV, which makes them suitable for solar cell applications. In this work, we study the electronic structure, optical properties, and the thickness dependence of the solar cell efficiencies of MX2 (M: Mo, W; X: S, Se, Te) with density functional theory and GW t BSE. Through this analysis, we find a change in solar cell efficiency trends at slab thicknesses of 3 μm. For thin films solar cells (thicknesses smaller than 3 μm), the tellurides present the highest efficiencies (about 20% for a 100 nm thick slab). In contrast, for thicknesses greater than 3 μm, our results indicate that a maximum solar cell efficiency can be achieved in WS2. For instance, a 100 μm slab of WS2 presents a solar cell efficiency of 36.3%, making this material a promising candidate for solar cell applications.
关键词： Thin film,First-principles,DFT,Solar cell,Transition metal dichalcogenides,GWtBSE
更新于2025-09-19 17:13:59
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Photoactivated transition metal dichalcogenides to boost electron extraction for all-inorganic tri-brominated planar perovskite solar cells
摘要： The band-energy structure, electron mobility and electronic trap states of electron-transporting layer (ETL) are critical for perovskite solar cells (PSCs). However, the state-of-the-art titanium oxide (TiO2) ETL prepared by means of high-temperature processing technology requires a long preparation time and more energy consumption; and the low-temperature processed species always present unfavourable electrical properties. In this work, we demonstrate the photoactivated transition metal dichalcogenides quantum dots (TMDCs QDs, MoS2 and MoSe2) boosted low-temperature processed TiO2 (L-TiO2) ETL for all-inorganic CsPbBr3 PSCs free of hole-transporting layer and precious metal electrode. Arising from the photo-generated electron injection from TMDCs QDs to L-TiO2 under light irradiation, the electronic trap states and the electron mobility of ETL have been effectively regulated, which in turn significantly enhances the electron extraction from perovskite to L-TiO2 ETL and reduces the carrier recombination. Finally, the optimal CsPbBr3 PSC achieves an enhanced power conversion efficiency of 10.02% with an ultrahigh open-circuit voltage of 1.615 V and excellent long-term stability, providing a new path to efficient photovoltaic devices.
关键词： perovskite solar cells,transition metal dichalcogenides,photoactivation,electron-transporting layer,quantum dots
更新于2025-09-19 17:13:59
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Spatially Controlled Lateral Heterostructures of Graphene and Transition Metal Dichalcogenides toward Atomically Thin and Multi-Functional Electronics
摘要： Edge contacts between two-dimensional (2D) materials in the in-plane direction can achieve minimal contact area and low contact resistance, producing atomically thin devices with improved performance. Specifically, lateral heterojunctions of metallic graphene and semiconducting transition metal dichalcogenides (TMDs) exhibit small Schottky barrier heights due to graphene’s low work-function. However, issues exist with fabrication of highly transparent and flexible multi-functional devices utilizing lateral heterostructures (HSs) of graphene and TMDs via spatially controlled growth. This review demonstrates growth and electronic applications of lateral HSs of graphene and TMDs, highlighting key technologies controlling wafer-scale growth of continuous films for practical applications. It deepens the understanding of the spatially controlled growth of lateral HSs using chemical vapor deposition methods, and also contribute to the applications for the scale-up of all-2D electronics with ultra-high electrical performance.
关键词： electronic applications,graphene,lateral heterostructures,chemical vapor deposition,transition metal dichalcogenides
更新于2025-09-19 17:13:59
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Plasmonic Pt Superstructures with Boosted Near‐Infrared Absorption and Photothermal Conversion Efficiency in the Second Biowindow for Cancer Therapy
摘要： Defects are commonly found in two-dimensional (2D) transition-metal dichalcogenide (TMD) materials. Such defects usually dictate the optical and electrical properties of TMDs. It is thus important to develop techniques to characterize the defects directly with good spatial resolution, specificity, and throughput. Herein, we demonstrate that Kelvin probe force microscopy (KPFM) is a versatile technique for this task. It is able to unveil defect heterogeneity of 2D materials with a spatial resolution of 10 nm and energy sensitivity better than 10 meV. KPFM mappings of monolayer WS2 exhibit interesting work function variances that are associated with defects distribution. This finding is verified by aberration-corrected scanning transmission electron microscopy and density functional theory calculations. In particular, a strong correlation among the work function, electrical and optical responses to the defects is revealed. Our findings demonstrate the potential of KPFM as an effective tool for exploring the intrinsic defects in TMDs.
关键词： transition-metal dichalcogenides,density functional theory,defects,Kelvin probe force microscopy,scanning transmission electron microscopy,work function,two-dimensional materials
更新于2025-09-19 17:13:59
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Plasmonically enabled two-dimensional material-based optoelectronic devices
摘要： Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, black phosphorus and hexagonal boron nitride, have been intensively investigated as building blocks for optoelectronic devices in the past few years. Very recently, significant efforts have been devoted to the improvement of the optoelectronic performances of 2D materials, which are restricted by their intrinsically low light absorption due to the ultrathin thickness. Making use of the plasmonic effects of metal nanostructures as well as intrinsic plasmon excitation in graphene has been shown to be one of the promising strategies. In this minireview, recent progresses in 2D material-based optoelectronics enabled by the plasmonic effects are highlighted. A perspective on more possibilities in plasmon-assisted 2D material-based optoelectronic applications will also be provided.
关键词： Transition metal dichalcogenides,Plasmonic effects,Two-dimensional materials,Black phosphorus,Hexagonal boron nitride,Graphene,Optoelectronic devices
更新于2025-09-19 17:13:59
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High‐Performance Flexible Broadband Photodetectors Based on 2D Hafnium Selenosulfide Nanosheets
摘要： 2D transition-metal dichalcogenides have attracted significant interest in recent years due to their multiple degrees of freedom, allowing for tuning their physical properties via band engineering and dimensionality adjustment. The study of ternary 2D hafnium selenosulfide HfSSe (HSS) high-quality single crystals grown with the chemical vapor transport (CVT) technique is reported. An as-grown HSS single crystal exhibits excellent phototransistor performance from the visible to the near-infrared with outstanding stability. A giant photoresponsivity (≈6.4 × 104 A W?1 at 488 nm) and high specific detectivity (≈1014 Jones) are exhibited by a device fabricated by exfoliating single-crystal HSS of nano-thickness on a rigid Si/SiO2 substrate. The application of HSS single crystal is extended to yield a sensible flexible photodetector of photoresponsivity up to ≈1.3 A W?1 at 980 nm. The photoresponsivity of CVT-grown HSS single crystal is significantly larger than those fabricated with other existing Hf-based chalcogenides. The results suggest that the layered multi-elemental 2D chalcogenide single crystals hold great promise for future wearable electronics and integrated optoelectronic circuits.
关键词： crystal growth,photoresponsivity,transition metal dichalcogenides,flexible optoelectronics,specific detectivity
更新于2025-09-19 17:13:59
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Ultrasensitive Multilayer MoS <sub/>2</sub> a??Based Photodetector with Permanently Grounded Gate Effect
摘要： 2D materials, specifically MoS2 semiconductors, have received tremendous attention for photo-sensing applications due to their tunable bandgap and low noise levels. A unique photodetector using multilayer MoS2 as the semiconductor channel, in which the gate electrode of the device is permanently connected to the grounded source electrode to introduce rectification, is reported. The proposed grounded-gate photodiode exhibits high photo-responsivity of 1.031 A W?1, excellent photodetectivity (>6 × 1010 jones), and highly stable rise/fall time response (100–200 ms) under illumination of visible light (at the wavelengths of 405, 532, and 638 nm). Numerical device simulations using quantum transport methods and photoconductive effects are used to explain the device operation. It is also suggested that the gate metal work function can be carefully chosen to increase the sensitivity of the grounded-gate photodetector by suppressing the dark current. The grounded-gate device proposed, owing to the properties of rectifying behavior, low contact resistance, consistent photoresponsivity, and linear sensitivity, provides a new platform for next-generation applications in the field of electronics and optoelectronics.
关键词： photodetectors,molybdenum disulfide,grounded-gate effect,photodiodes,transition metal dichalcogenides
更新于2025-09-19 17:13:59
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A new metal transfer process for van der Waals contacts to vertical Schottky-junction transition metal dichalcogenide photovoltaics
摘要： Two-dimensional transition metal dichalcogenides are promising candidates for ultrathin optoelectronic devices due to their high absorption coefficients and intrinsically passivated surfaces. To maintain these near-perfect surfaces, recent research has focused on fabricating contacts that limit Fermi-level pinning at the metal-semiconductor interface. Here, we develop a new, simple procedure for transferring metal contacts that does not require aligned lithography. Using this technique, we fabricate vertical Schottky-junction WS2 solar cells, with Ag and Au as asymmetric work function contacts. Under laser illumination, we observe rectifying behavior and open-circuit voltage above 500 mV in devices with transferred contacts, in contrast to resistive behavior and open-circuit voltage below 15 mV in devices with evaporated contacts. One-sun measurements and device simulation results indicate that this metal transfer process could enable high specific power vertical Schottky-junction transition metal dichalcogenide photovoltaics, and we anticipate that this technique will lead to advances for two-dimensional devices more broadly.
关键词： van der Waals contacts,transition metal dichalcogenides,photovoltaics,metal transfer process,Schottky-junction
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Investigation of Photoluminescence Properties of 2D-Nanoparticles to be Used as Fluorescence Markers in Microscopy
摘要： Transition metal dichalcogenides (TMDs) are direct bandgap semiconductors [1], and they exhibit fascinating optical properties, such as valley polarization, room temperature excitons, and high optical nonlinearity. Single and few-layer TMDs and TMD-nanoparticles exhibit much stronger photoluminescence than the bulk material [2]. This property makes them an attractive candidate for use as mesoscale fluorescent markers, e.g., for use in fluorescence microscopy. As opposed to conventional fluorescent markers, such as fluorescent molecules they do not exhibit phototoxicity and have been shown to be biocompatible in contrast to, e.g., many types of quantum dots. Here we focus on the characterization of MoS2 and WS2 nanoparticles, obtained through liquid phase exfoliation [3], from powdered precursors. Sonication of TMD powder in N-Methyl pyrrolidone (NMP) is carried out, as NMP and single layer TMDs have comparable surface energies to prevent the restacking of exfoliated nanosheets. The resulting solution was found to have particles of a typical size of 65 nm, which have been investigated for PL-spectra and long-term PL-behaviour, such as blinking and bleaching. Structural analysis reveals (See Fig.1 (a)) that we have a mixture of particles and particle agglomerates. PL spectra show that both exhibit comparable spectral signatures with peak wavelengths (Fig. 1(b)) ranging from 600 to 640nm. The excitation wavelength was 532nm. We find that these results indicate, that TMD-nanoparticles are suitable, e.g., for use as fluorescent guide stars [4] in adaptive optical microscopy in inhomogeneous samples, e.g., tissue. 2D-nanoparticles would be infiltrated into the sample, and the PL-emission could be used by a combination of a wavefront-sensor and an adaptive optical element to undo the effects of scattering in the vicinity of the particle. This method would leverage the strong PL, biocompatibility and long-term stability of the 2D-nanoparticles, to allow for longer observation cycles in sensitive samples, such as living tissue.
关键词： nanoparticles,photoluminescence,biocompatibility,fluorescence microscopy,Transition metal dichalcogenides
更新于2025-09-16 10:30:52
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In situ TEM observation of controlled growth of two-dimensional WS2 with vertically aligned layers and high-temperature stability
摘要： Layered transition metal dichalcogenides with vertically aligned morphology show great potentials in energy conversion and storage due to the high density of exposed edge sites which have enhanced electrochemical reactivity. In this letter, through in situ heating investigations in a transmission electron microscope, the controlled growth of vertically aligned WS2 with high-temperature stability has been achieved through the thermolysis of solid precursor K2WS4. It is found that the growth of vertically aligned WS2 layers employs hybrid growth modes, in which the growth of new WS2 slab is initiated at old ones from either the middle part or edge part. These vertically aligned WS2 layers show great stability at high temperature of 900°C. Our detailed investigations and theoretical calculations indicate that potassium element in the solid precursor plays a critical role in the growth and evolution of vertically aligned WS2. This method is also applicable to the controlled growth of vertically aligned MoS2 with high-temperature stability through the decomposition of K2MoS4. These findings pave a way for tailored design and fabrication of materials with optimized structure to achieve their superior properties.
关键词： Vertical growth,In situ,High-temperature stability,Transition metal dichalcogenides,TEM
更新于2025-09-16 10:30:52