Triplet Excitation and Electroluminescence from a Supramolecular Monolayer Embedded in a Boron Nitride Tunnel Barrier

Svatek, Simon A.; Kerfoot, James; Summerfield, Alex; Nizovtsev, Anton S.; Korolkov, Vladimir V.; Taniguchi, Takashi; Watanabe, Kenji; Antol�n, Elisa; Besley, Elena; Beton, Peter H.

Abstract

© 2019 American Chemical Society. 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/two-dimensional hybrid tunneling diode. Electrons can tunnel 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 hν > eVSD, indicating upconversion by energies up to ∼1 eV. We show that tunneling 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 upconversion.

Citation

Svatek, S. A., Kerfoot, J., Summerfield, A., Nizovtsev, A. S., Korolkov, V. V., Taniguchi, T., Watanabe, K., Antolín, E., Besley, E., & Beton, P. H. (2020). Triplet Excitation and Electroluminescence from a Supramolecular Monolayer Embedded in a Boron Nitride Tunnel Barrier. Nano Letters, 20(1), 278-283. https://doi.org/10.1021/acs.nanolett.9b03787

• Journal Article Type: Article
• Acceptance Date: Dec 10, 2019
• Online Publication Date: Dec 10, 2019
• Publication Date: Jan 8, 2020
• Deposit Date: Jan 8, 2020
• Publicly Available Date: Feb 29, 2020
• Journal: Nano Letters
• Print ISSN: 1530-6984
• Electronic ISSN: 1530-6992
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 20
• Issue: 1
• Pages: 278-283
• DOI: https://doi.org/10.1021/acs.nanolett.9b03787
• Keywords: Mechanical Engineering; General Materials Science; Bioengineering; General Chemistry; Condensed Matter Physics
• Public URL: https://nottingham-repository.worktribe.com/output/3610841
• Publisher URL: https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.9b03787