Electroluminescence from Single-Walled Carbon Nanotubes with Quantum Defects

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Single-walled carbon nanotubes (SWCNTs) with covalent sidewall defects are tunable photon sources.
• Their optical properties depend on chirality and functionalization.

Purpose of the Study:

• To investigate electroluminescence (EL) from functionalized SWCNTs.
• To correlate EL with electrical transport and photoluminescence (PL).
• To demonstrate gate-controlled, defect-induced emissions.

Main Methods:

• Fabrication of single-tube devices using functionalized (7, 5) and (6, 5) SWCNTs with graphene electrodes.
• Electroluminescence spectroscopy and excitation mapping.
• Electrical transport measurements.
• Photoluminescence spectroscopy of pristine and functionalized nanotubes.

Main Results:

• Electrically generated, defect-induced emissions were observed and controllable by electrostatic gating.
• Emissions were strongly red-shifted compared to pristine nanotubes.
• Excitonic and trionic recombination processes were identified.
• Gate-dependent emission lines at cryogenic conditions were assigned to phonon-assisted hot-exciton EL.
• High spectral purity was achieved through gate control of defect-state emission.

Conclusions:

• Electroluminescence excitation selectively targets neutral defect states with low transition energy.
• Gate control allows differentiation between neutral and charged defect emissions.
• Functionalized SWCNTs offer a pathway to highly pure, tunable light sources.