| Autor: |
Svatek SA, Kerfoot J, Summerfield A, Nizovtsev AS; Nikolaev Institute of Inorganic Chemistry , Siberian Branch of the Russian Academy of Sciences , Academician Lavrentiev Avenue 3 , Novosibirsk 630090 , Russian Federation., Korolkov VV, Taniguchi T; National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Ibaraki , Japan., Watanabe K; National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Ibaraki , Japan., Antolín E; Instituto de Energía Solar , Universidad Politécnica de Madrid , Avenida Complutense 30 , Madrid 28040 , Spain., Besley E, Beton PH |
| Abstrakt: |
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 V SD , and we observe molecular electroluminescence from an excited singlet state with an emitted photon energy hν > eV SD , 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. |
