Defect Induced Photoluminescence from Dark Excitonic States in Individual Single-Walled Carbon Nanotubes

TL;DR

This study demonstrates that defect-induced mixing in single-walled carbon nanotubes enables dark excitonic states to emit photoluminescence, revealing new low-energy PL bands and altered exciton dynamics.

Contribution

It introduces a method to generate PL from dark excitons in nanotubes via defect-induced state mixing, expanding understanding of excitonic behavior.

Findings

New low-energy PL bands observed in nanotubes

Dark excitons can be brightened through defects

Dark state lifetimes are longer and not thermally equilibrated

Abstract

We show that new low-energy photoluminescence (PL) bands can be created in semiconducting single-walled carbon nanotubes by intense pulsed excitation. The new bands are attributed to PL from different nominally dark excitons that are "brightened" due to defect-induced mixing of states with different parity and/or spin. Time-resolved PL studies on single nanotubes reveal a significant reduction of the bright exciton lifetime upon brightening of the dark excitons. The lowest energy dark state has longer lifetimes and is not in thermal equilibrium with the bright state.