Fluorescent Carbon Nanotube Defects Manifest Substantial Vibrational Reorganization

Abstract

Fluorescent defects have opened up exciting new opportunities to chemically tailor semiconducting carbon nanotubes for imaging, sensing, and photonics needs such as lasing, single photon emission, and photon upconversion. However, experimental measurements on the trap depths of these defects show a puzzling energy mismatch between the optical gap (difference in emission energies between the native exciton and defect trap states) and the thermal detrapping energy determined by application of the van ’t Hoff equation. To resolve this fundamentally important problem, here we synthetically incorporated a series of fluorescent aryl defects into semiconducting single-walled carbon nanotubes and experimentally determined their energy levels by temperature-dependent and chemically correlated evolution of exciton population and photoluminescence. We found that depending on the chemical nature and density of defects, the exciton detrapping energy is 14–77% smaller than the optical gap determined from photoluminesce...