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 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 similar to 5x10(-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 ps that, when combined with a predicted natural radiative lifetime of similar to 20 ns, suggests that the true PLQY is similar to 6.5x10(-3). Finally, deconvoluted PL excitation spectra are produced for eight SWNT species, and the appearance of a higher-energy excitonic subband is discussed.