Understanding the excitation wavelength dependent spectral shift and large exciton binding energy of tungsten disulfide quantum dots and its interaction with single-walled carbon nanotubes

Single-layer MoS 2 has been reported to exhibit strong excitonic and trionic signatures in its photoluminescence (PL) spectra. Here, we report that the emission spectra of MoS 2 QDs strongly depend on the dielectric constant of the solvent and the relative difference in the electronegativity between the solvent and QDs. Due to the difference in electronegativity, electrons are either added to the QD or withdrawn from it. Consequently, depending upon the dielectric permittivity and the electronegativity of the surrounding medium, the signature peaks of excitons and trions exhibit a significant change in the PL spectra of MoS 2 QDs. Our findings are helpful to understand the effect of the surrounding environment on the optical properties of QDs and the importance of the selection of solvent since MoS 2 QDs are potential candidates for valleytronics applications.

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“… 29 However, when QDs are formed, due to the addition of quantum confinement, it will likely increase the trion binding energy. 39 − 41 …”

Section: Resultsmentioning

confidence: 99%

Excitons and Trions in MoS₂ Quantum Dots: The Influence of the Dispersing Medium

Thomas

Jinesh

2022

ACS Omega

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“…Tungsten disulfide quantum dots (QDs) and its interaction with single walled carbon nanotubes were prepared. 10 High optical band gap, large exciton binding energy and high fluorescence quantum yield were mentioned. Mechanical properties of tungsten disulfide monolayer for machine learning were studied.…”

Section: Introductionmentioning

confidence: 99%

The WS₂ dependence on the elasticity and optical band gap energies of swollen PAAm composites

Evingür

Sağlam

Çimen

et al. 2020

Journal of Composite Materials

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New generation nano-filler polymer composites have many applications including biomedical, electronic and maritime related applications because of their mechanical, electronic and optical properties. The properties of composites were investigated as a function of nano-filler content. Among these, tungsten disulfide (WS2) has the potential to be used as a component in electronic devices owing to its high electron mobility and easily tunable optical band gap energy. Tungsten disulfide (WS2)- Polyacrylamide (PAAm) composite was prepared using free radical co-polymerization and wet laboratory methods with WS2 content. Composites were characterized for mechanical and optical properties using an Elasticity Instrument and UV-vis Spectrophotometer, respectively. Elastic modulus was modeled by a statistical thermodynamics model. Tauc’s and Urbach’s Tail model for direct transition were used to model for the optical band gap. In this study, the swelling and WS2 effect on the optical band gap and elasticity of WS2 - PAAm composites were investigated. It was observed that the elasticity presented a reversed behavior of optical band gap energies with respect to WS2 content. For the applications of nano-filler doped polymer composites in flexible electronic devices, WS2 content strongly influences the mechanical and optical properties.

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“…The emission was selected at 540 nm to examine the effect of Au NPs on excitonic decay. Each decay spectrum fits well with a biexponential decay function Here, τ 1 and τ 2 are the carrier lifetimes for the fast and the slow recombination processes, respectively, , and A 1 and A 2 are the respective strengths. We evaluate the average carrier lifetime (τ av ) for both the cases using the relation .…”

Section: Results and Discussionmentioning

confidence: 96%

“…The movement and loss of charges in opposite directions avoiding recombination effectively gives rise to faster decay of PL in the Au-incorporated system. It may be noted that the recombination lifetime of WS 2 QDs/Si is lower than that of standalone WS 2 QDs, which is also attributed to charge separation at the junction between QDs to Si …”

Section: Results and Discussionmentioning

confidence: 99%

“…About 80 mg of high-purity (99%) WS 2 powder (Sigma-Aldrich) was dispersed in 80 mL of N -methyl-2-pyrrolidinone (NMP) (Alfa Aesar, 95%), and liquid exfoliation was carried out using a probe sonicator (Sonic Ruptor 250, Omni International) at a frequency of 20 kHz for 15 h. The solution was then centrifuged at 12 000 rpm for 45 min at 4 °C ambient temperature. The supernatant, which contained the as-prepared WS 2 QDs, was separated from the settled residue or the centrifugate . The excess solvent from the supernatant was then allowed to be evaporated with constant magnetic stirring at 750 rpm.…”

Section: Methodsmentioning

confidence: 99%

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Highly Suppressed Dark Current and Fast Photoresponse from Au Nanoparticle-Embedded, Si/Au/WS₂ Quantum-Dot-Based, Self-Biased Schottky Photodetectors

Bora

Mawlong

Giri

2021

ACS Appl. Electron. Mater.

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Two-dimensional semiconductor-based heterojunction photodetectors with ultralow dark current and fast photoresponse are highly desirable for cutting-edge optoelectronic applications. Herein, we study the role of embedded plasmonic Au nanoparticles (NPs) in the photoresponse characteristics of heterojunction photodetectors (PDs) consisting of n-type WS2 quantum dots (QDs) decorated on a p-type Si substrate. The Si/WS2 photodetector without the Au NPs has a fast response/recovery time of ∼55.1/139.8 μs and a photocurrent-to-dark current ratio (I on/I off) of ∼227. By integrating the Au NPs sandwiched between the Si/WS2 QD junctions, the device showed outstanding photodetection performance compared to the Si/WS2 PD. The Si/Au/WS2 Schottky heterojunction device exhibits an astounding I on/I off ratio of ∼1.3 × 105 due to the decrease in the dark current by about 2 orders of magnitude as well as an increase in photocurrent by about 1 order of magnitude and significantly faster rise/fall times of ∼4.4/43.5 μs. The underlying mechanism behind the ultralow dark current and high on/off ratio is investigated in detail. The faster photoresponse is attributed to hot electron transfer as well as carrier tunneling from Au NPs to WS2 QDs. The peak responsivity and detectivity of the fabricated Si/Au/WS2 detector are estimated at ∼276 A/W and ∼4.3 × 1013 Jones, respectively, at an applied bias of 5 V and under 405 nm illumination. Notably, both the devices function as self-powered PDs. Moreover, the Au NP-incorporated hybrid system exhibits an ∼6-fold enhancement in the photoluminescence (PL) as compared to bare WS2 QDs owing to the surface plasmon resonance. We use a theoretical model to calculate the field enhancement factor in the vicinity of WS2 QDs due to the Au NPs and show that the experimental data match very well with the theoretical value at the chosen excitation wavelength. These results indicate that integrating plasmonic nanoparticles with the Si/WS2 QD PD holds great potential for applications in future high-performance optoelectronic devices.

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Understanding the excitation wavelength dependent spectral shift and large exciton binding energy of tungsten disulfide quantum dots and its interaction with single-walled carbon nanotubes

Cited by 37 publications

References 58 publications

Excitons and Trions in MoS₂ Quantum Dots: The Influence of the Dispersing Medium

Excitons and Trions in MoS₂ Quantum Dots: The Influence of the Dispersing Medium

The WS₂ dependence on the elasticity and optical band gap energies of swollen PAAm composites

Highly Suppressed Dark Current and Fast Photoresponse from Au Nanoparticle-Embedded, Si/Au/WS₂ Quantum-Dot-Based, Self-Biased Schottky Photodetectors

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Understanding the excitation wavelength dependent spectral shift and large exciton binding energy of tungsten disulfide quantum dots and its interaction with single-walled carbon nanotubes

Cited by 37 publications

References 58 publications

Excitons and Trions in MoS2 Quantum Dots: The Influence of the Dispersing Medium

Excitons and Trions in MoS2 Quantum Dots: The Influence of the Dispersing Medium

The WS2 dependence on the elasticity and optical band gap energies of swollen PAAm composites

Highly Suppressed Dark Current and Fast Photoresponse from Au Nanoparticle-Embedded, Si/Au/WS2 Quantum-Dot-Based, Self-Biased Schottky Photodetectors

Contact Info

Product

Resources

About

Excitons and Trions in MoS₂ Quantum Dots: The Influence of the Dispersing Medium

Excitons and Trions in MoS₂ Quantum Dots: The Influence of the Dispersing Medium

The WS₂ dependence on the elasticity and optical band gap energies of swollen PAAm composites

Highly Suppressed Dark Current and Fast Photoresponse from Au Nanoparticle-Embedded, Si/Au/WS₂ Quantum-Dot-Based, Self-Biased Schottky Photodetectors