Triplet excitations in carbon nanostructures

Abstract

We show that the energy differences between the lowest optical singlet exciton and the lowest triplet exciton in semiconducting single-walled carbon nanotubes with diameter $\sim 1$ nm and graphene nanoribbons with widths $\sim 2$ nm are an order of magnitude smaller than in the $\pi$-conjugated polymer poly(para-phenylenevinylene). Our calculated energy gaps between the singlet and triplet excitons are in excellent agreement with the measured values in three different nanotubes with diameters close to 1 nm. The spatial extent of the triplet exciton is nearly the same as that of the singlet exciton in wide nanotubes and nanoribbons, in contrast to that in $\pi$-conjugated polymers, in which the triplet exciton exhibits strong spatial confinement. Weakly confined behavior of the triplet state begins in nanoribbons with widths as narrow as 2.5 times the graphene unit lattice vector. We discuss possible consequences of the small singlet-triplet energy difference in the carbon nanostructures on device applications.

9 pages, 2 tables, 4 figures

References in corpus (12)

• Peculiar Width Dependence of the Electronic Property of Carbon Nanoribbons
• Quantum spin-liquid emerging in two-dimensional correlated Dirac fermions
• Electron-electron interaction effects on optical excitations in semiconducting single-walled carbon nanotubes
• Optical properties of graphene nanoribbons: the role of many-body effects
• Magnetic Brightening of Carbon Nanotube Photoluminescence through Symmetry Breaking
• Triplet absorption in carbon nanotubes: a TD-DFT study
• Defect Induced Photoluminescence from Dark Excitonic States in Individual Single-Walled Carbon Nanotubes
• Universal properties of quasi-one-dimensional excitons in semiconducting single-walled carbon nanotubes and $\pi$-conjugated polymers
• Theory of Electro-Optical Properties of Graphene Nanoribbons
• Quantitative calculations of the excitonic energy spectra of semiconducting single-walled carbon nanotubes within a $\pi$-electron model
• pi-Electron theory of transverse optical excitons in semiconducting single-walled carbon nanotubes
• Excitonic Effects in the Optical Spectra of Graphene Nanoribbons

Cited by in corpus (1)

• Inter-valley scattering induced by Coulomb interaction and disorder in carbon-nanotube quantum dots