Emergent Above-Gap Photoluminescence in Molecularly Engineered Hybrid Bilayer Crystals

Bilayer crystals, built by stacking two-dimensional (2D) covalent monolayers, give rise to coupled excitonic states whose properties are constrained by fixed lattice symmetry and orientation. Replacing one covalent monolayer with a 2D molecular crystalheld together by noncovalent forcesovercomes t...

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Հիմնական հեղինակ:	Tomojit Chowdhury (6285287) (author)
Այլ հեղինակներ:	Aurélie Champagne (15213726) (author), Patrick Knüppel (22676009) (author), Zehra Naqvi (20934322) (author), Ariana Ray (7651370) (author), Mengyu Gao (5545958) (author), David A. Muller (1568509) (author), Nathan P. Guisinger (1383159) (author), Kin Fai Mak (1901236) (author), Jeffrey B. Neaton (1262847) (author), Jiwoong Park (1661347) (author)
Հրապարակվել է:	2025
Խորագրեր:	Biophysics Cell Biology Biotechnology Ecology Computational Biology Astronomical and Space Sciences not elsewhere classified Chemical Sciences not elsewhere classified Physical Sciences not elsewhere classified strong polarization anisotropy perfectly linear power peak 120 mev directly growing single based bilayer platform atomically thin optoelectronic ab initio </ plane lattice geometry fixed lattice symmetry delocalized excitonic states fully quenches pl demonstrating molecular control 7 </ sup 2 </ sub gap emission  excitonic emission lattice scale gap emission excitonic phenomena ∼ 10 work introduces stacking two robust photoluminescence report four quantum materials ptcda monolayer powerful knob law dependence intermolecular spacing interlayer coupling give rise gap photoluminescence exciton engineering excitation density excellent agreement coexisting localized calculations reveal
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Ամփոփում:	Bilayer crystals, built by stacking two-dimensional (2D) covalent monolayers, give rise to coupled excitonic states whose properties are constrained by fixed lattice symmetry and orientation. Replacing one covalent monolayer with a 2D molecular crystalheld together by noncovalent forcesovercomes this limitation, as molecular functional groups afford tunable in-plane lattice geometry, intermolecular spacing, and interlayer coupling, providing a powerful knob for exciton engineering. Here, we report four-atom-thick hybrid bilayer crystals (HBCs) synthesized by directly growing single-crystalline PDI molecular crystal atop WS<sub>2</sub> monolayers, which exhibit a robust photoluminescence (PL) peak 120 meV above the WS<sub>2</sub> optical band gap alongside a below-gap emission. Both peaks display strong polarization anisotropynearing unity for the above-gap emissionand maintain a perfectly linear power-law dependence up to an excitation density of ∼10<sup>7</sup> mW/cm<sup>2</sup>, indicative of coexisting localized and delocalized excitonic states. Substituting PDI with a PTCDA monolayer on WS<sub>2</sub> fully quenches PL, demonstrating molecular control over excitonic emission. Lattice scale <i>ab initio</i> GW and Bethe–Salpeter equation (BSE) calculations reveal a significantly hybridized bilayer band structure in PDI/WS<sub>2</sub> that supports interlayer excitonic species both above and below the WS<sub>2</sub> gap with strong polarization anisotropy, in excellent agreement with experiment. Our work introduces a molecule-based bilayer platform for the bottom-up design and control of excitonic phenomena in atomically thin optoelectronic and quantum materials.

Emergent Above-Gap Photoluminescence in Molecularly Engineered Hybrid Bilayer Crystals

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