Probing Trions at Chemically Tailored Trapping Defects

Abstract

Trions, charged excitons that are reminiscent of hydrogen and positronium ions, have been intensively studied for energy harvesting, light-emitting diodes, lasing, and quantum computing applications because of their inherent connection with electron spin and dark excitons. However, these quasi-particles are typically present as a minority species at room temperature making it difficult for quantitative experimental measurements. Here, we show that by chemically engineering the well depth of sp3 quantum defects through a series of alkyl functional groups covalently attached to semiconducting carbon nanotube hosts, trions can be efficiently generated and localized at the trapping chemical defects. The exciton-electron binding energy of the trapped trion approaches 119 meV, which more than doubles that of “free” trions in the same host material (54 meV) and other nanoscale systems (2–45 meV). Magnetoluminescence spectroscopy suggests the absence of dark states in the energetic vicinity of trapped trions. Unexpectedly, the trapped trions are approximately 7.3-fold brighter than the brightest previously reported and 16 times as bright as native nanotube excitons, with a photoluminescence lifetime that is more than 100 times larger than that of free trions. These intriguing observations are understood by an efficient conversion of dark excitons to bright trions at the defect sites. This work makes trions synthetically accessible and uncovers the rich photophysics of these tricarrier quasi-particles, which may find broad implications in bioimaging, chemical sensing, energy harvesting, and light emitting in the short-wave infrared.

Efficient MoWO3/VO2/MoS2/Si UV Schottky photodetectors; MoS2 optimization and monoclinic VO2 surface modifications

“…Trion is defined as a quasi-particle that can potentially carry out more information and data than electrons for which make them useful towards different applications such as optoelectronics and quantum computing 56 . Trions are consisting of three charged particles bound together by very weak bonding energy that makes them quickly fall apart 57 . It is known that the dominated peak in Figs.…”

Interaction of Luminescent Defects in Carbon Nanotubes with Covalently Attached Stable Organic Radicals

“…Conceptually, the situation is analogous to that of defect-trapped trions in SWCNTs. 55 In both cases, the spin state does not change upon optical transition from the excited to the ground state, thus resulting in a vanishing spin Zeeman effect.…”

Photon Correlation Spectroscopy of Luminescent Quantum Defects in Carbon Nanotubes

“…In CNTs decorated with sp 3 -defects that promote localization of both neutral excitons and trions, two respective PL bands with emission energies well below the one-dimensional energy continuum of diffusive E 11 excitons have been observed at the ensemble level. 22,26 At the level of individual nanotubes, a detailed understanding of the exciton population distribution among these distinct PL states would provide guidelines for further developments of chemically functionalized CNTs for applications in optical sensing and quantum photonics.…”

“…17,22 The chemical side-wall treatment gives rise to one or more defects per tube with deep trap potentials characterized by PL bands of neutral excitons (X) and trions (T). 22,26 As covalent CNT chemistry is known to favor proximal defects 27 via defect-assisted local destabilization of the carbon lattice with subsequent formation of a second defect in immediate proximity, the enhanced probability of divalent defect formation 28 is common in functionalized nanotubes. The related PL spectra of defect-decorated CNTs are thus rich in diversity, with frequent peak multiplicity in cryogenic single-tube PL.…”

“…This scenario is shown schematically in Figure 4e, where the charge state of the neighboring defects is anticorrelated due to repulsive Coulomb interaction among the excess electrons residing on covalent hexyl chains. 22 In the level diagram of Figure 4e, this is represented by electron hopping between the two defect states.…”