Unveiling exciton many-body interactions in WS2 single crystal

Taank, Pravrati; Adarsh, K. V.

doi:10.1063/5.0060842

Cited by 4 publications

(4 citation statements)

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“…The TA line shape is a combination of bleach (negative) signals at the A and B exciton resonances and absorption (positive) signals on the red and blue sides of the exciton bleach. Overall, the spectroscopic features revealed by TA measurements are a combined effect of the bandgap renormalization, Stark shift, and carrier‐induced broadening 26–32 …”

Section: Resultsmentioning

confidence: 99%

“…3 First, we studied the TA spectrum of few-layer MoS 2 nanosheets with 3.10 eV pump excitation, which generates excitons and free carriers. 14,15,25 The contour plots of TA of few-layer MoS [26][27][28][29][30][31][32] To better understand the exciton and free carrier recombination mechanism at 3.10 eV pump excitation, we have plotted fluence-dependent bleach decay kinetics of A exciton, as shown in Figure 3C.…”

Section: Resultsmentioning

confidence: 99%

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Exciton recombination in few‐layer MoS₂ nanosheets: Role of free carriers and defects

Taank

Karmakar

Adarsh

2023

Surface & Interface Analysis

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A current obstacle to the development of extremely flexible and high‐performance optoelectronic devices using transition metal dichalcogenide nanosheets is the incomplete understanding of the exciton and free carrier recombination in the presence of defects. Here, taking liquid‐phase exfoliated few‐layer MoS2 nanosheets as a model system, we demonstrate the exciton and free carrier recombination mechanism by employing pump energy and fluence‐dependent ultrafast transient absorption spectroscopy. We demonstrate that 3.10 eV pump excitation, much above the lowest energy A exciton of four to six layers of MoS2 nanosheets (~1.84 eV), generates excitons and free carriers. The excitons decay quickly within ~3 ps due to the defect capture via the Shockley–Read–Hall mechanism. In contrast, free carriers show slower recombination (~1000 ps), which is an order of magnitude larger than the exciton recombination time. We verified this idea by exciting the sample with 1.94–2.22 eV pump excitations that predominantly generate excitons decaying within ~3 ps. Our systematic studies in few‐layer MoS2 nanosheets reveal crucial information on the unexplored domain of excitons and free carriers recombination in the presence of defects for several optoelectronic applications.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Exciton recombination in few‐layer MoS₂ nanosheets: Role of free carriers and defects

Taank

Karmakar

Adarsh

2023

Surface & Interface Analysis

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“…[35][36][37][38][39][40] Likewise, the TA spectra of WS2-NT in Figure 3b shows bleach at the exciton positions and PIA at ~2.0 eV originating from the blueshift of the exciton resonance due to the exciton Stark-shift and the formation of the polaritonic states. 35,[41][42][43] Strikingly, Cs4PbBr6/WS2-NT shows a complex TA spectrum consisting of a series of bleach at excitonic resonances and PIA at both sides of the bleach (Figure 3c). Notably, the excitonic positions are slightly redshifted compared to the pristine systems.…”

Section: Resultsmentioning

confidence: 99%

Enhanced photocatalytic activity of Cs4PbBr6/WS2 hybrid nanocomposite

Immanuel

Huang

Taank

et al. 2022

Preprint

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Photocatalytic processes are among the prime means for mitigating the pollution caused by toxic effluents. In this context, photocatalysis presents a promising path and undergoing rapid evolution. Halide perovskites (HPs) are excellent candidates due to their negative conduction band minimum and the low work function that are essential for photocatalysis. Interestingly, HPs performance significantly improves by introducing transitional-metal dichalcogenides as a co-catalyst, which enables suppressed charge recombination. Here we investigate the photocatalytic performance of Cs4PbBr6/WS2 nanocomposites towards organic dye degradation under visible light illumination. We found that the Cs4PbBr6/WS2 nanostructures significantly increase the degradation rate of methylene blue compared to pristine Cs4PbBr6 nanocrystals. The transient absorption measurements reveal charge transfer from Cs4PbBr6 to WS2. The results of our study imply that the boosted photocatalytic performance of the nanocomposites is due to the reduced carrier recombination. Our findings pave the way for the implementation of Cs4PbBr6/WS2 nanocomposites as superior photocatalysts.

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“…[49] Likewise, the TA spectrum of WS 2 -NTs in Figure 3b shows instantaneous bleach at the exciton positions (A exciton at ≈1.90 eV and B exciton at ≈2.27 eV) and a photo-induced absorption between A and B exciton at ≈2.00 eV originating from the blueshift of the exciton resonance due to the exciton Stark-shift and the formation of the polaritonic states. [33,[50][51][52] Strikingly, Cs 4 PbBr 6 /WS 2 -NTs hybrid nanocomposite shows temporal and spectral profile differences, see Figure 3c. We observed bleach at A exciton, initially at 1.90 eV, which was slightly redshifted ≈10 meV in the hybrid nanocomposite due to charge gained from Cs 4 PbBr 6 , indicating charge transfer from Cs 4 PbBr 6 -NCs to the WS 2 -NT.…”

Section: Ta Spectroscopymentioning

confidence: 99%

Enhanced Photocatalytic Activity of Cs₄PbBr₆/WS₂ Hybrid Nanocomposite

Immanuel,

Huang,

Taank

et al. 2023

Adv Energy and Sustain Res

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Photocatalytic processes are among the prime means for mitigating the pollution caused by toxic effluents. In this context, photocatalysis presents a promising path and is undergoing rapid evolution. Halide perovskite‐nanocrystals (HP‐NCs) are excellent candidates due to their negative conduction band minimum and low work function, essential for photocatalysis. Yet, HP‐NCs face limitations within this domain because they are prone to chemical degradation when exposed to external factors like high temperature, polar solvents, oxygen, and light. A practical approach toward stabilizing HP‐NCs involves hybridizing them with a chemically inert material that can provide steric stabilization and act as a cocatalyst. Transition‐metal dichalcogenides emerge as outstanding candidates to sterically stabilize the HPs as they are stable, chemically inert, and can serve as co‐catalysts, enabling suppressed charge recombination. Herein, the photocatalytic performance of Cs4PbBr6/WS2‐nanocomposites towards organic dye degradation in polar solvents under visible light illumination is investigated. We found that the presence of WS2 nanostructures significantly stabilizes the HP‐NCs and promotes dye degradation rate compared to pristine Cs4PbBr6‐NCs. Using transient absorption measurements, we found that the WS2‐nanostructures act as an electron transport channel, effectively reducing charge recombination in the NCs. These findings pave the way for implementing Cs4PbBr6/WS2‐nanocomposites as stable and superior photocatalysts.

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Unveiling exciton many-body interactions in WS2 single crystal

Cited by 4 publications

References 8 publications

Exciton recombination in few‐layer MoS₂ nanosheets: Role of free carriers and defects

Exciton recombination in few‐layer MoS₂ nanosheets: Role of free carriers and defects

Enhanced photocatalytic activity of Cs4PbBr6/WS2 hybrid nanocomposite

Enhanced Photocatalytic Activity of Cs₄PbBr₆/WS₂ Hybrid Nanocomposite

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Unveiling exciton many-body interactions in WS2 single crystal

Cited by 4 publications

References 8 publications

Exciton recombination in few‐layer MoS2 nanosheets: Role of free carriers and defects

Exciton recombination in few‐layer MoS2 nanosheets: Role of free carriers and defects

Enhanced photocatalytic activity of Cs4PbBr6/WS2 hybrid nanocomposite

Enhanced Photocatalytic Activity of Cs4PbBr6/WS2 Hybrid Nanocomposite

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Product

Resources

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Exciton recombination in few‐layer MoS₂ nanosheets: Role of free carriers and defects

Exciton recombination in few‐layer MoS₂ nanosheets: Role of free carriers and defects

Enhanced Photocatalytic Activity of Cs₄PbBr₆/WS₂ Hybrid Nanocomposite