Diamond Materials

Diamond Materials for Quantum Application

23. September 2014: The DFG research group FOR 1493 “Diamond Materials and Quantum Applications” goes into its second funding period. FOR1493 is a national research consortium funded by the Deutsche Forsch-ungsgemeinschaft.

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ERC Advanced Grant


Electrically driven photon antibunching from a single molecule

Single-photon emitters have been considered for applications in quantum information processing, quantum cryptography and metrology. For the sake of integration and to provide an electron photon interface, it is of great interest to stimulate single-photon emission by electrical excitation as it was demonstrated for quantum dots in 2002. Because of low exciton binding energies, it has so far not been possible to detect sub-Poissonian photon statistics of electrically driven quantum dots at room temperature. However, organic molecules possess exciton binding energies on the order of 1 eV, thereby facilitating the development of an electrically driven single-photon source at room temperature in a solid-state matrix. However, the choice of an appropriate molecular dopant for electrical excitation experiments is a non-trivial issue. In contrast to molecular photoexcitation experiments in which one usually chooses molecules with a high fluorescence quantum yield and low intersystem crossing probabilities (e.g. Terrylene in p-Terphenyl), in electroluminescence it is necessary to employ a molecular emitter which is able to emit photons using phosphorescence. This requirement results due to the underlying recombination statistics in organic light emitting devices which lead to a probability of 75% to excite the molecule’s triplet state and of 25% to excite the respective singlet state. For a molecule to be able to generate efficient phosphorescent emission, a heavy metal ion needs to be inserted into the molecular structure thereby increasing spin-orbit coupling and reducing the molecule’s triplet state radiative lifetime down to 1 µs. In this work, the organometallic complex Ir(piq) 3 emitting at 615 nm was used as phosphorescent dopant.

By applying low work function barium metal contacts, oxygen-free processing and efficient encapsulation techniques, we were able to design an organic light emitting device with spatial and temporal stable electroluminescence characteristics enabling the demonstration of non-classical electroluminescent emission originating from a single, electrically driven molecule at room temperature.

Electrically driven photon antibunching from a single molecule at room temperature
Nature Communications 10.1038/NCOMMS.1637

M. Nothaf t 1, S. Höhla 2, F. Jelezko 3, N. Frühauf 2, J. Pflaum 4 and J. Wrachtrup 1

1 3rd Physics Institute and Research Center SCoPE, University of Stuttgart, 70550 Stuttgart, Germany
2 Institute for Large Area Microelectronics and Research Center SCoPE, University of Stuttgart, 70550 Stuttgart, Germany
3 Institute for Quantum Optics, University of Ulm, 89069 Ulm, Germany
4 Experimental Physics VI, University of Würzburg and ZAE Bayern, 97074 Würzburg, Germany