Selective triplet exciton formation in a single molecule

Kimura, Kaname; Miwa, Kuniyuki; Imada, Hiroshi; Imai-Imada, Miyabi; Kawahara, Shota; Takeya, Jun; Kawai, Maki; Galperin, Michael; Kim, Yousoo

doi:10.1038/s41586-019-1284-2

Cited by 183 publications

(116 citation statements)

References 43 publications

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“…There have been several recent reports of OLEDs that exploit triplet fusion, whereby two triplets annihilate and produce an emissive singlet. [75][76][77] Although this limits IQE to a maximum of 50% (if only triplets are injected), it could allow for low driving voltages and may offer blue emitters with greater photostability than present compounds. There is a need to improve the chemistry used to synthesize organic semiconductors.…”

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confidence: 99%

The role of chemical design in the performance of organic semiconductors

et al. 2020

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Organic semiconductors are solution-processable, lightweight and flexible, such that they are increasingly being used as the active layer in a wide range of new technologies. The versatility of synthetic organic chemistry enables the materials to be tuned such that they can be incorporated into biological sensors, wearable electronics, semi-transparent photovoltaics and flexible displays. These devices can be improved not only by developing their synthetic chemistry but also by improving the analytical and computational techniques that enable us to understand the factors that govern material properties. Judicious molecular design provides control of the semiconductor frontier molecular orbital energy distribution and guides the hierarchical assembly of organic semiconductors into functional films where we can control the properties and motion of charges and excited states. This Review describes how molecular design plays an integral role in developing organic semiconductors for electronic devices in present and emerging technologies. [H1] Molecular orbital design considerations The energies of frontier molecular orbitals and the distribution of the orbitals in a π-conjugated molecule play critical roles in intra-and intermolecular charge transport, light absorption/emission, charge injection/extraction/trapping and electrochemistry. This is true for organic small molecules and conjugated polymers alike. In each case, the energy of the highest occupied molecular orbital (HOMO) largely depends on the electron density and delocalization of the π electrons throughout a π-conjugated backbone. Substituents that donate electron density mesomerically (for example, lone pair donation from N, O or S heteroatoms) or inductively (for example, alkyl chains) can contribute to raising the HOMO energy EHOMO, decreasing the solid-state ionization potential (IP, Box 1). Conversely electronwithdrawing groups, such as-F,-C(O)R or-C≡N groups, can act to lower both the HOMO and lowest unoccupied molecular orbital (LUMO) energy, leading to an increase in the solid-state electron affinity (EA). BOX 1 | Energy levels in an isolated organic molecule and a molecular crystal or polymer.

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confidence: 99%

The role of chemical design in the performance of organic semiconductors

et al. 2020

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“…In this context, electroluminescence from single molecules has been recently established through self-decoupling ( 24 ) or by introducing ultrathin insulating layers ( 25 ) between the molecule and a noble metal substrate. In addition, STML has enabled vibronic spectroscopy with submolecular resolution ( 25 , 26 ), imaging molecular orbitals through photon emission maps ( 27 , 28 ), studying charge and exciton dynamics ( 24 , 29 , 30 ), and stimulating spin-selective optical transitions ( 31 ). STML on indium tin oxide–supported MoSe 2 has also been recently reported and attributed to radiative decay of the A exciton in this material ( 32 ).…”

Section: Resultsmentioning

confidence: 99%

Electrically driven photon emission from individual atomic defects in monolayer WS ₂

et al. 2020

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Quantum dot–like single-photon sources in transition metal dichalcogenides (TMDs) exhibit appealing quantum optical properties but lack a well-defined atomic structure and are subject to large spectral variability. Here, we demonstrate electrically stimulated photon emission from individual atomic defects in monolayer WS2 and directly correlate the emission with the local atomic and electronic structure. Radiative transitions are locally excited by sequential inelastic electron tunneling from a metallic tip into selected discrete defect states in the WS2 bandgap. Coupling to the optical far field is mediated by tip plasmons, which transduce the excess energy into a single photon. The applied tip-sample voltage determines the transition energy. Atomically resolved emission maps of individual point defects closely resemble electronic defect orbitals, the final states of the optical transitions. Inelastic charge carrier injection into localized defect states of two-dimensional materials provides a powerful platform for electrically driven, broadly tunable, atomic-scale single-photon sources.

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“…allows to identify a finite subset, which is enough for first principles simulation of experimental data for realistic systems. [54][55][56][57][58] Contacts (baths) are assumed to be reservoirs of free charge carriers each at its own equilibrium.…”

Section: Modelmentioning

confidence: 99%

Electron Transfer Methods in Open Systems

Bergmann

Galperin

2019

J. Phys. Chem. B

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Utilization of electron transfer methods for description of quantum transport is popular due to simplicity of the formulation and its ability to account for basic physics of electron exchange between system and baths. At the same time, necessity to go beyond simple golden rule-type expressions for rates was indicated in the literature and ad hoc formulations were proposed. Similarly, kinetic schemes for quantum transport beyond usual second order Lindblad/Redfield considerations were discussed. Here we utilize recently introduced by us nonequilibrium Hubbard Green's functions diagrammatic technique to analyze construction of rates in open systems. We show that previous considerations for rates of second and fourth order can be obtained as a particular case of zero and second order Green's function diagrammatic series with bare diagrams.We discuss limitations of previous considerations, stress advantages of the Hubbard Green's function approach in constructing the rates and indicate that standard dressing of the diagrams is a natural way to account for additional baths/degrees of freedom when formulating generalized expressions for the rates.

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Selective triplet exciton formation in a single molecule

Cited by 183 publications

References 43 publications

The role of chemical design in the performance of organic semiconductors

The role of chemical design in the performance of organic semiconductors

Electrically driven photon emission from individual atomic defects in monolayer WS ₂

Electron Transfer Methods in Open Systems

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Selective triplet exciton formation in a single molecule

Cited by 183 publications

References 43 publications

The role of chemical design in the performance of organic semiconductors

The role of chemical design in the performance of organic semiconductors

Electrically driven photon emission from individual atomic defects in monolayer WS 2

Electron Transfer Methods in Open Systems

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Electrically driven photon emission from individual atomic defects in monolayer WS ₂