Quantum Energy and Charge Transfer at Two-Dimensional Interfaces

Bradac, Carlo; Xu, Zai‐Quan; Aharonovich, Igor

doi:10.1021/acs.nanolett.0c04152

Cited by 36 publications

(48 citation statements)

References 65 publications

(138 reference statements)

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“…[ 30 ] Alternatively, the photocarriers relaxation in HS can be understood as an excitonic state transition [ 30,31 ] or bilateral charge exchange rather than a net charge transfer, which is like the Dexter type transfer process. [ 32,39–41 ] This is supported by our observation that both electrons and holes show a cooling process after charge separation. On the other hand, the valley polarization of electron and hole is also fundamentally important to understand the charge transfer mechanism, because only it can give direct information about the state‐to‐state transition.…”

Section: Resultssupporting

confidence: 65%

“…The exchange rate is given by k exchange = KJe −2R/L , where R is the donor−acceptor distance, L is the sum of their van der Waals radii, J is the normalized spectral overlap integral, and K is a parameter related to the orbital overlap. [39][40][41] Since the Dexter-type process is not sensitive to driving force, dielectric environments, and temperature, the robust charge transfer in TMD HSs could be easily understood. [24][25][26] The Dexter-type transfer is a short-range process, and the rate exponentially depends on the donor−acceptor distance.…”

Section: Resultsmentioning

confidence: 99%

“…[24][25][26] The Dexter-type transfer is a short-range process, and the rate exponentially depends on the donor−acceptor distance. [39][40][41] It is worth to testify whether the same mechanism is held for the energy transfer between interlayer excitons. We designed a trilayer-HS MoS 2 -WSe 2 -WS 2 that combines two well-studied bilayer-HS MoS 2 -WSe 2 and WSe 2 -WS 2 (Figure 1 shows the Raman spectra and steady absorption spectra of MoS 2 -WSe 2 -WS 2 ).…”

Section: Resultsmentioning

confidence: 99%

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Dexter‐Type Exciton Transfer in van der Waals Heterostructures

Zheng

Wang

et al. 2022

Adv Funct Materials

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Van der Waals (vdW) heterostructures (HSs) built on 2D materials provide an ideal platform for research of energy migration at the nanoscale. However, the underlying charge transfer mechanism in type II vdW HSs is still not well understood. Here, ultrafast exciton dynamics are investigated in trilayer-WS 2 -MoS 2 -WSe 2 and trilayer-MoS 2 -WSe 2 -WS 2 HSs by broadband pump-probe spectroscopy. A two-step process of exciton transfer in trilayer-WS 2 -MoS 2 -WSe 2 is directly observed when the band edge exciton of WSe 2 is excited. The electrons in WSe 2 are initially transferred to the high lying electronic state of MoS 2 -WS 2 on a time scale of tens of femtoseconds, and then electrons eventually relax into the conduction band minimum of MoS 2 within 1 ps. Furthermore, the transfer of interlayer excitons is observed for the first time in trilayer-MoS 2 -WSe 2 -WS 2 . Both transfer processes can be better understood by the Dexter charge exchange model. Due to the nature of Dexter type transfer that the exchange rate exponentially depends on the donor−acceptor distance, the interlayer exciton transfer rate is nearly a hundred times slower than that of exciton transition in bilayer HSs. The results deepen the understanding of charge transfer in 2D vdW HSs and also indicate that the exciton effect and orbital hybridization make HS a strong coupling system.

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Section: Resultssupporting

confidence: 65%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Dexter‐Type Exciton Transfer in van der Waals Heterostructures

Zheng

Wang

et al. 2022

Adv Funct Materials

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“… 70 , 84 Consequently, in BNP and CCP , a charge carrier transport between the pyrene planes should be possible. 68 , 70 , 85 , 86 While the overlap area of two stacked molecules of BNP is 35%, it is largely elevated in CCP (58%), which is comparable with unsubstituted pyrene (60%) and a number of substituted pyrenes that throughout exhibit excimer formation in the solid state. 68 We will discuss the consequences of this overlap angle on the optical properties later in the article.…”

Section: Resultsmentioning

confidence: 97%

BN-Substitution in Dithienylpyrenes Prevents Excimer Formation in Solution and in the Solid State

et al. 2022

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Boron–nitrogen substitutions in polycyclic aromatic hydrocarbons (PAHs) have a strong impact on the optical properties of the molecules due to a significantly more heterogeneous electron distribution. However, besides these single-molecule properties, the observed optical properties of PAHs critically depend on the degree of intermolecular interactions such as π–π-stacking, dipolar interactions, or the formation of dimers in the excited state. Pyrene is the most prominent example showing the latter as it exhibits a broadened and strongly bathochromically shifted emission band at high concentrations in solution compared to the respective monomers. In the solid state, the impact of intermolecular interactions is even higher as it determines the crystal packing crucially. In this work, a thiophene-flanked BN-pyrene ( BNP ) was synthesized and compared with its all-carbon analogue ( CCP ) in solution and in the solid state by means of crystallography, NMR spectroscopy, UV–vis spectroscopy, and photoluminescence (PL) spectroscopy. In solution, PL spectroscopy revealed the solvent-dependent presence of excimers of CCP at high concentrations. In contrast, no excimers were found in BNP . Clear differences were also observed in the single-crystal packing motifs. While CCP revealed overlapped pyrene planes with centroid distances in the range of classical π-stacking interactions, the BNP scaffolds were displaced and significantly more spatially separated.

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“…[4][5][6] Recently, vertical stacks of monolayer (1L) TMDCs have gained a growing attention as van der Waals (vdW) heterostructures with unmatched characteristics suitable for dynamic control over the essential aspects of the interlayer coupling and energy transfer channels. [7][8][9][10] The geometric arrangement, layer charge polarization, and valley polarization endow interlayer excitons with intriguing physics and applications. [11][12][13][14] Up to now, most studies on the interlayer energy transfer are focused on Förster energy transfer and charge transfer when the separation distance is <20 nm or one tenth of the wavelength.…”

Section: Introductionmentioning

confidence: 99%

Engineering Radiative Energy Transfer and Directional Excitonic Emission in van der Waals Heterostructures

Mao

Yang

Taghinejad

et al. 2022

Laser & Photonics Reviews

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Controlling excitonic energy transfer in 2D van der Waals (vdW) heterostructures is crucial for photonic and optoelectronic applications. Recent studies suggest that the interlayer energy transfer in vdW heterostructures is strongly correlated with the vertical interlayer spacing. However, the interlayer coupling with large separations (>20 nm) when the radiative energy transfer is dominant has not been studied yet. In this case, excitons as radiative dipole sources are able to control the light field. Here, the thickness dependency of radiative energy transfer in vertical vdW heterostructures of WS2 (tungsten disulfide)/hBN (hexagonal boron nitride)/WS2 is studied. The excitonic emission of WS2/hBN and WS2/hBN/WS2 heterostructures is engineered with the intensity ratios of heterostructures to monolayers ranging from 5% to 250%. More importantly, by changing the stacking order to control whether forward or backward emission is collected, a controllable directivity of the excitonic emission from 0.6 to 6.0 is achieved. In theory, the tunability to high‐index/mid‐index interferences and dipole–dipole far‐field coupling is attributed. The outcomes of the study on the radiative energy transfer of vdW heterostructures containing 1Ls (monolayers) with excitonic effects and MLs (multilayers) with high refractive indices will pave the way toward the realization of all vdW nanophotonics.

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Quantum Energy and Charge Transfer at Two-Dimensional Interfaces

Cited by 36 publications

References 65 publications

Dexter‐Type Exciton Transfer in van der Waals Heterostructures

Dexter‐Type Exciton Transfer in van der Waals Heterostructures

BN-Substitution in Dithienylpyrenes Prevents Excimer Formation in Solution and in the Solid State

Engineering Radiative Energy Transfer and Directional Excitonic Emission in van der Waals Heterostructures

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