Analysis of photoluminescence from solubilized single-walled carbon nanotubes

The functional form of the photoluminescence (PL) line shape from individual single-walled carbon nanotube (SWNT) species is found to contain a significant Lorentzian component and the Stokes shift is observed to be very small $(<8\mathrm{meV})$, which suggests an excitonic dephasing mechanism that is largely decoupled from surrounding solvent and surfactant molecules. The PL quantum yield (PLQY) of two SWNT species is determined to be $\sim 5\times {10}^{-4}$, and it is suggested that this is lower than the “true” value due to quenching of the PL in bundles by metallic tubes. Time-resolved PL measurements reveal a dominant, luminescence lifetime component of $130\mathrm{ps}$ that, when combined with a predicted natural radiative lifetime of $\sim 20\mathrm{ns}$, suggests that the true PLQY is $\sim 6.5\times {10}^{-3}$. Finally, deconvoluted PL excitation spectra are produced for eight SWNT species, and the appearance of a higher-energy excitonic subband is discussed.