Spectral features due to dark exciton in photoluminescence map of single-walled carbon nanotubes

Features in Photoluminescence Map of SWNTs Over the past seven years photoluminescence (PL) spectroscopy has emerged as an important characterization tool for determining the (n, m) chirality and population of semiconducting SWNTs. This technique is essential for the chirality selective growth and/or the separation depending on chirality. Under excitation with the appropriate wavelength of light, SWNTs exhibit characteristic peaks with well-defined emission from their corresponding excitonic states. Besides the quantum yield of the photoluminescence, sound understanding of extra features mainly due to dark exciton are necessary, in order to use this PL map for the determination of chirality population of SWNTs. Such features are shown in Fig. 1, where the sample contains only (7,5) and a trace of (6,5); at least within PL spectroscopic measure. Optical absorption by excitonic phonon sideband due to mixing of dark exciton and K phonon (marked as E11+K and E22+K) is well discussed [1]. And, the cross-polarized absorption marked as E12 is confirmed [2]. Here, the phonon sideband in emission (E11K) and quasi-dark exciton in cross-polarized excitation (E12) are discussed.