Excited-state carrier lifetime in single-walled carbon nanotubes

We measured the near-infrared photoluminescence decay time in several different-chirality single-walled carbon nanotubes by time-resolved picosecond luminescence spectroscopy. Together with the results of resonant pump-and-probe spectroscopy this leads to a carrier lifetime in the first excited state of semiconducting nanotubes exceeding 30 ps, which is one order of magnitude larger than the carrier dynamics observed in nanotube bundles. Our findings show that the absence of photoluminescence in nanotube bundles is due to a tunneling of the free carriers from semiconducting into metallic nanotubes.