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Exciton

About: Exciton is a research topic. Over the lifetime, 31603 publications have been published within this topic receiving 810642 citations.


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Journal ArticleDOI
TL;DR: This work addresses common features of CT excitons at both types of van der Waals interfaces and emphasizes the competition between localization and delocalization in ensuring efficient charge separation at the molecular donor/acceptor interface.
Abstract: The van der Waals interfaces of molecular donor/acceptor or graphene-like two-dimensional (2D) semiconductors are central to concepts and emerging technologies of light-electricity interconversion. Examples include, among others, solar cells, photodetectors, and light emitting diodes. A salient feature in both types of van der Waals interfaces is the poorly screened Coulomb potential that can give rise to bound electron–hole pairs across the interface, i.e., charge transfer (CT) or interlayer excitons. Here we address common features of CT excitons at both types of interfaces. We emphasize the competition between localization and delocalization in ensuring efficient charge separation. At the molecular donor/acceptor interface, electronic delocalization in real space can dictate charge carrier separation. In contrast, at the 2D semiconductor heterojunction, delocalization in momentum space due to strong exciton binding may assist in parallel momentum conservation in CT exciton formation.

256 citations

Journal ArticleDOI
TL;DR: In this paper, the electronic structure and properties of the orthorhombic phase of the perovskite are computed with density functional theory, and the structure, optimized using a van der Waals functional, reproduces closely the unit cell volume.
Abstract: The electronic structure and properties of the orthorhombic phase of the $\mathrm{CH}{}_{3}\mathrm{NH}{}_{3}\mathrm{PbI}{}_{3}$ perovskite are computed with density functional theory. The structure, optimized using a van der Waals functional, reproduces closely the unit cell volume. The experimental band gap is reproduced accurately by combining spin-orbit effects and a hybrid functional in which the fraction of exact exchange is tuned self-consistently to the optical dielectric constant. Including spin-orbit coupling strongly reduces the anisotropy of the effective mass tensor, predicting a low electron effective mass in all crystal directions. The computed binding energy of the unrelaxed exciton agrees with experimental data, and the values found imply a fast exciton dissociation at ambient temperature. Also polaron masses for the separated carriers are estimated. The values of all these parameters agree with recent indications that fast dynamics and large carrier diffusion lengths are key in the high photovoltaic efficiencies shown by these materials.

255 citations

Journal ArticleDOI
TL;DR: The absence of band-gap renormalization in the laser emission indicates a marked increase in the stability of the exciton in one dimension.
Abstract: Stimulated optical emission from the lowest exciton state in atomically smooth semiconductor quantum wires is observed for the first time. The wires are formed by the ssT intersection of two 7 nm GaAs quantum wells. The optical emission wavelength is nearly independent of pump levels. This absence of band-gap renormalization in the laser emission indicates a marked increase in the stability of the exciton in one dimension.

255 citations

Journal ArticleDOI
TL;DR: In this article, an exact correspondence between Coulomb blockade in the device's vertical transport properties and Pauli blocking in the transmission spectra is established, and substantial shifts, up to 20 meV, in the energies of higher excitations on occupation of the electron ground state are observed.
Abstract: Interband excitations of an ensemble of InAs self-assembled quantum dots have been directly observed in transmission experiments. The dots are embedded in a field-effect structure allowing us to load the dots electrically. We establish an exact correspondence between Coulomb blockade in the device's vertical transport properties and Pauli blocking in the transmission spectra. We observe substantial shifts, up to 20 meV, in the energies of the higher excitations on occupation of the electron ground state. We argue that this is a consequence of an exciton-electron interaction.

254 citations

Journal ArticleDOI
TL;DR: In this article, the authors derived the ratio between mobility and diffusion parameters for a Gaussian-like density of states for a wide range of organic materials (polymers or small molecules) and showed that there is an inherent dependence of the transport in trap-free disordered organic materials on the charge density.
Abstract: The ratio between mobility and diffusion parameters is derived for a Gaussian-like density of states. This steady-state analysis is expected to be applicable to a wide range of organic materials (polymers or small molecules) as it relies on the existence of quasiequilibrium only. Our analysis shows that there is an inherent dependence of the transport in trap-free disordered organic materials on the charge density. The implications for the contact phenomena and exciton generation rate in light emitting diodes as well as channel width in field-effect transistors is discussed.

253 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,269
20222,623
20211,045
20201,157
20191,096
20181,057