Band gap in tungsten sulphoselenide single crystals determined by the optical absorption method

Gujarathi, D. N.; Solanki, G. K.; Deshpande, M. P.; Agarwal, M. K.

doi:10.1016/j.mssp.2005.07.001

Cited by 12 publications

(6 citation statements)

References 19 publications

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“…1c. In general, four main Raman modes can be observed in the range from 225 to 450 cm -1 , including A1g(Se-W) mode (259.7 cm -1 ), E2g(S-W) mode (356.5 cm -1 ), A1g(S-W-Se) mode (380.5 cm -1 ) and A1g(S-W) mode (403.2 cm -1 ), consistent with previous reports [19][20][21][22] . The co-existence of A1g mode for W-S and W-Se indicates that there is some random distribution of the S and Se 24 , and the studied WS0.6Se1.4 is not a monolayer Janus alloy 26,45 .…”

supporting

confidence: 91%

“…The tunable optical bandgap of the alloy TMDs, therefore, facilitate valleytronics applications when the excitation light wavelength is fixed. Despite the recent surge of interest on monolayer TMD alloys [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] , the optical properties reported are limited by the quality of the sample and many questions remain open. Will the monolayer semiconductor alloy TMD still maintain the valley polarization?…”

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confidence: 99%

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Excitonic Complexes and Emerging Interlayer Electron–Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS_0.6Se_1.4

Meng

Wang

et al. 2018

Nano Lett.

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Monolayer transition metal dichalcogenides (TMDs) possess superior optical properties, including the valley degree of freedom that can be accessed through the excitation light of certain helicity. While WS2 and WSe2 are known for their excellent valley polarization due to the strong spin-orbit coupling, the optical bandgap is limited by the ability to choose from only these two materials. This limitation can be overcome through the monolayer alloy semiconductor, WS2xSe2(1-x), which promises an atomically thin semiconductor with tunable bandgap. In this work, we show that the high-quality BN encapsulated monolayer WS0.6Se1.4 inherits the superior optical properties of tungsten-based TMDs, including a trion splitting of ~ 6 meV and valley polarization as high as ~60%. In particular, we demonstrate for the first time the emerging and gate-tunable interlayer electron-phonon coupling in the BN/WS0.6Se1.4/BN van der Waals heterostructure, which renders the otherwise optically silent Raman modes visible. In addition, the emerging Raman signals can be drastically enhanced by the resonant coupling to the 2s state of the monolayer WS0.6Se1.4 A exciton. The BN/WS2xSe2(1-x)/BN van der Waals heterostructure with a tunable bandgap thus provides an exciting platform for exploring the valley degree of freedom and emerging excitonic physics in two-dimension.

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confidence: 91%

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confidence: 99%

Excitonic Complexes and Emerging Interlayer Electron–Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS_0.6Se_1.4

Meng

Wang

et al. 2018

Nano Lett.

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“…The structure of the as-prepared BHJ OSC and its corresponding energy band diagram are illustrated in Figure b,c, respectively. It is worth noting that the electronic band gap of WSe 2 is thickness dependent passing from an indirect bandgap of 0.8 eV in the bulk material to a direct bandgap of 1.3 eV in the single-layer limit. − Recent studies demonstrated that defects in WSe 2 flakes, e . g ., atomic vacancies/additions, doping, structural defects, change their electronic properties. − In particular, the edge-oxidation of WSe 2 flakes can increase the electronic bandgap up to ∼1.5 eV …”

Section: Resultsmentioning

confidence: 99%

Size-Tuning of WSe₂ Flakes for High Efficiency Inverted Organic Solar Cells

Kakavelakis

Castillo²,

Pellegrini³

et al. 2017

ACS Nano

100

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The development of large-scale production methods of two-dimensional (2D) crystals, with on-demand control of the area and thickness, is mandatory to fulfill the potential applications of such materials for photovoltaics. Inverted bulk heterojunction (BHJ) organic solar cell (OSC), which exploits a polymer-fullerene binary blend as the active material, is one potentially important application area for 2D crystals. A large ongoing effort is indeed currently devoted to the introduction of 2D crystals in the binary blend to improve the charge transport properties. While it is expected that the nanoscale domains size of the different components of the blend will significantly impact the performance of the OSC, to date, there is no evidence of quantitative information on the interplay between 2D crystals and fullerene domains size. Here, we demonstrate that by matching the size of WSe few-layer 2D crystals, produced by liquid-phase exfoliation, with that of the PCBM fullerene domain in BHJ OSCs, we obtain power conversion efficiencies (PCEs) of ∼9.3%, reaching a 15% improvement with respect to standard binary devices (PCE = 8.10%), i.e., without the addition of WSe flakes. This is the highest ever reported PCE for 2D material-based OSCs, obtained thanks to the enhanced exciton generation and exciton dissociation at the WSe-fullerene interface and also electron extraction to the back metal contact as a consequence of a balanced charge carriers mobility. These results push forward the implementation of transition-metal dichalcogenides to boost the performance of BHJ OSCs.

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“…Besides, strain engineering will alter the structural symmetry, which may give rise to the polarized characteristics of 2D materials and endow them with great prospects in future applications. As has been reported, the strained WSe 2 monolayers show obvious variation in electronic band structure [18][19][20][21][22] and demonstrate unique advantages in the applications of photoactive devices [23], valleytronics [18,24], photodetectors [25], and anode material for Li-ion battery [26]. Nevertheless, strain engineering on the electronic and optical properties, such as band evolution and optical anisotropy of 2D Janus WSSe bilayer has not yet been reported so far.…”

Section: Introductionmentioning

confidence: 99%

Strain Engineering on the Electronic and Optical Properties of WSSe Bilayer

Guo

et al. 2020

Nanoscale Res Lett

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Controllable optical properties are important for optoelectronic applications. Based on the unique properties and potential applications of two-dimensional Janus WSSe, we systematically investigate the strain-modulated electronic and optical properties of WSSe bilayer through the first-principle calculations. The preferred stacking configurations and chalcogen orders are determined by the binding energies. The bandgap of all the stable structures are found sensitive to the external stress and could be tailored from semiconductor to metallicity under appropriate compressive strains. Atomic orbital projected energy bands reveal a positive correlation between the degeneracy and the structural symmetry, which explains the bandgap evolutions. Dipole transition preference is tuned by the biaxial strain. A controllable transformation between anisotropic and isotropic optical properties is achieved under an around − 6%~− 4% critical strain. The strain controllable electronic and optical properties of the WSSe bilayer may open up an important path for exploring next-generation optoelectronic applications.

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Band gap in tungsten sulphoselenide single crystals determined by the optical absorption method

Cited by 12 publications

References 19 publications

Excitonic Complexes and Emerging Interlayer Electron–Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS_0.6Se_1.4

Excitonic Complexes and Emerging Interlayer Electron–Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS_0.6Se_1.4

Size-Tuning of WSe₂ Flakes for High Efficiency Inverted Organic Solar Cells

Strain Engineering on the Electronic and Optical Properties of WSSe Bilayer

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Band gap in tungsten sulphoselenide single crystals determined by the optical absorption method

Cited by 12 publications

References 19 publications

Excitonic Complexes and Emerging Interlayer Electron–Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS0.6Se1.4

Excitonic Complexes and Emerging Interlayer Electron–Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS0.6Se1.4

Size-Tuning of WSe2 Flakes for High Efficiency Inverted Organic Solar Cells

Strain Engineering on the Electronic and Optical Properties of WSSe Bilayer

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Product

Resources

About

Excitonic Complexes and Emerging Interlayer Electron–Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS_0.6Se_1.4

Excitonic Complexes and Emerging Interlayer Electron–Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS_0.6Se_1.4

Size-Tuning of WSe₂ Flakes for High Efficiency Inverted Organic Solar Cells