Abstract
Low-energy, dark excitonic states have recently been predicted to lie below the first bright () exciton in semiconducting single-walled carbon nanotubes [Phys. Rev. Lett. 93, 157402 (2004)]. Decay into such deep excitonic states is implicated as a mechanism which reduces photoluminescence quantum yields. In this study we report the first direct observation of deep excitons in SWNTs. Photoluminescence (PL) microscopy of suspended semiconducting single-walled carbon nanotubes (SWNTs) reveals weak emission satellites redshifted by and relative to the main PL emission peaks. Similar satellites, redshifted by 95–145 meV depending on nanotube species, were also found in PL measurements of ensembles of SWNTs in water-surfactant dispersions. The relative intensities of these deep exciton emission features depend on the nanotube surroundings.
- Received 11 May 2007
DOI:https://doi.org/10.1103/PhysRevLett.99.237402
©2007 American Physical Society