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arXiv · 1909.08488

Triplet excitation and electroluminescence from a supramolecular monolayer embedded in a boron nitride tunnel barrier

Simon A. Svatek·James Kerfoot·Alex Summerfield·Anton S. Nizovtsev·Vladimir V. Korolkov·Takashi Taniguchi·Kenji Watanabe·Elisa Antolín·Elena Besley·Peter H. Beton
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Abstract

We show that ordered monolayers of organic molecules stabilized by hydrogen bonding on the surface of exfoliated few-layer hexagonal boron nitride (hBN) flakes may be incorporated into van der Waals heterostructures with integral few-layer graphene contacts forming a molecular/2D hybrid tunneling diode. Electrons can tunnel from through the hBN/molecular barrier under an applied voltage VSD and we observe molecular electroluminescence from an excited singlet state with an emitted photon energy > eVSD, indicating up-conversion by energies up to ~ 1 eV. We show that tunnelling electrons excite embedded molecules into singlet states in a two-step process via an intermediate triplet state through inelastic scattering and also observe direct emission from the triplet state. These heterostructures provide a solid-state device in which spin-triplet states, which cannot be generated by optical transitions, can be controllably excited and provide a new route to investigate the physics, chemistry and quantum spin-based applications of triplet generation, emission and molecular photon up-conversion.

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Simon A. Svatek, James Kerfoot, Alex Summerfield, Anton S. Nizovtsev, Vladimir V. Korolkov, Takashi Taniguchi, Kenji Watanabe, Elisa Antolín, Elena Besley, Peter H. Beton. 2019-09-18. Triplet excitation and electroluminescence from a supramolecular monolayer embedded in a boron nitride tunnel barrier. https://doi.org/10.1021/acs.nanolett.9b03787

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