Using an Atomically Thin Layer of Hexagonal Boron Nitride to Separate Bound Charge-Transfer Excitons at Organic Interfaces

Wanigasekara, Shanika; Rijal, Kushal; Rudayni, Fatimah; Panth, Mohan; Shultz, A.; Wu, Judy; Chan, Wai‐Lun

doi:10.1103/physrevapplied.18.014042

Cited by 4 publications

(2 citation statements)

References 55 publications

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“…A band of excited states centered at an energy ∼0.2 eV above the Fermi level E f is observed. Very similar TR-TPPE spectra can be found in ZnPc films deposited on various substrates. − Following our previous works, we assigned this peak to the ZnPc’s S 1 exciton. The S 1 population is not immediately quenched by the metal layer (Al) because the ZnPc is separated from Al by the native oxide layer on the Al surface (Figure a).…”

Section: Resultssupporting

confidence: 52%

Ultrafast and Long-Range Energy Transfer from Plasmon to Molecular Exciton

et al. 2023

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By using a model interface consisting of a metallic grating and zinc phthalocyanine (ZnPc) molecules, we temporally and spatially resolve the energy transfer process from plasmon to molecular exciton via the plasmon-induced resonance energy transfer mechanism. It is found that the energy transfer can occur within 30 fs for a distance of 20 nm. The energy transfer range is much larger than that of typical hot carrier transfer and molecule-to-molecule energy transfer processes. Hence, this ultrafast and long-range plasmon-induced energy transfer channel is especially useful for boosting the exciton/free carrier generation yield in semiconductor layers. Moreover, the enhancement in the exciton production yield does not diminish even when the photon energy is lowered toward the optical absorption edge of ZnPc. Therefore, the observed energy transfer process can extend the optical absorption to frequencies below the optical bandgap of the molecule.

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Section: Resultssupporting

confidence: 52%

Ultrafast and Long-Range Energy Transfer from Plasmon to Molecular Exciton

et al. 2023

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“…To further understand how the electron delocalization across the organic film would affect the IX trapping, we study the IX’s dynamics as a function of the organic film thickness. Because the TR-TPPE technique is only sensitive to electrons residing near the sample surface (for organic materials, the probe depth is ∼1–3 nm − ), the thickness-dependent measurement can probe the spatial localization/delocalization of the electron in the IX along the surface normal direction, , which is parallel to the π-stacking direction of the molecules. Figure a,b shows the temporal evolution of the IX’s peak intensity for different film thicknesses for PTCDI/MoS 2 and PTCDA/MoS 2 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Nanoscale Periodic Trapping Sites for Interlayer Excitons Built by Deformable Molecular Crystal on 2D Crystal

et al. 2023

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The nanoscale moirépattern formed at 2D transition-metal dichalcogenide crystal (TMDC) heterostructures provides periodic trapping sites for excitons, which is essential for realizing various exotic phases such as artificial exciton lattices, Bose−Einstein condensates, and exciton insulators. At organic molecule/TMDC heterostructures, similar periodic potentials can be formed via other degrees of freedom. Here, we utilize the structure deformability of a 2D molecular crystal as a degree of freedom to create a periodic nanoscale potential that can trap interlayer excitons (IXs). Specifically, two semiconducting molecules, PTCDI and PTCDA, which possess similar band gaps and ionization potentials but form different lattice structures on MoS 2 , are investigated. The PTCDI lattice on MoS 2 is distorted geometrically, which lifts the degeneracy of the two molecules within the crystal's unit cell. The degeneracy lifting results in a spatial variation of the molecular orbital energy, with an amplitude and periodicity of ∼0.2 eV and ∼2 nm, respectively. On the other hand, no such energy variation is observed in PTCDA/MoS 2 , where the PTCDA lattice is much less distorted. The periodic variation in molecular orbital energies provides effective trapping sites for IXs. For IXs formed at PTCDI/MoS 2 , rapid spatial localization of the electron in the organic layer toward the interface is observed, which demonstrates the effectiveness of these interfacial IX traps.

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Modulation of Electrostatic Potential in 2D Crystal Engineered by an Array of Alternating Polar Molecules

Fuller,

Rudayni,

Amos

et al. 2024

Nano Lett.

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The moiré potential in rotationally misfit two-dimensional (2D) heterostructures has been used to build artificial exciton and electron lattices, which have become platforms for realizing exotic electronic phases. Here, we demonstrate a different approach to create a superlattice potential in 2D crystals by using the near field of an array of polar molecules. A bilayer of titanyl phthalocyanine (TiOPc), consisting of alternating out-of-plane dipoles, is deposited on monolayer MoS2. Time-resolved two-photon photoemission spectroscopy reveals a pair of interlayer exciton states with an energy difference of ∼0.1 eV, which is consistent with the electrostatic potential modulation induced by the TiOPc bilayer as determined by density functional theory calculations. Because the symmetry and the period of this potential superlattice can be changed readily by using molecules of different shapes and sizes, molecule/2D heterostructures can be promising platforms for designing artificial exciton and electron lattices.

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Using an Atomically Thin Layer of Hexagonal Boron Nitride to Separate Bound Charge-Transfer Excitons at Organic Interfaces

Cited by 4 publications

References 55 publications

Ultrafast and Long-Range Energy Transfer from Plasmon to Molecular Exciton

Ultrafast and Long-Range Energy Transfer from Plasmon to Molecular Exciton

Nanoscale Periodic Trapping Sites for Interlayer Excitons Built by Deformable Molecular Crystal on 2D Crystal

Modulation of Electrostatic Potential in 2D Crystal Engineered by an Array of Alternating Polar Molecules

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