Singlet fission in chiral carbon nanotubes: Density functional theory based computation

Area of Science:

• Materials Science
• Quantum Chemistry
• Nanotechnology

Background:

• Singlet fission (SF) is a key mechanism for multiple exciton generation (MEG), crucial for advanced photovoltaic technologies.
• Chiral single-wall carbon nanotubes (SWCNTs) exhibit efficient SF within the solar spectrum, making them promising for solar energy applications.

Purpose of the Study:

• To investigate the SF exciton-to-biexciton and biexciton-to-exciton decay rates in various chiral SWCNTs.
• To explore the impact of surface functionalization, specifically with chlorine atoms, on SF and MEG efficiency in SWCNTs.

Main Methods:

• Density functional theory (DFT) simulations combined with many-body perturbation theory.
• Calculation of exciton-to-biexciton (R1→2) and biexciton-to-exciton (R2→1) decay rates for pristine and functionalized SWCNTs.

Main Results:

• Efficient SF rates (R1→2 ~ 10^14-10^15 s^-1) were predicted for chiral SWCNTs within the solar energy range.
• Biexciton-to-exciton recombination was found to be weak (R2→1/R1→2 ≤ 10^-2).
• Chlorine functionalization of (6,2) SWCNTs demonstrated potential for enhancing MEG by altering low-energy electronic states.

Conclusions:

• Chiral SWCNTs are effective platforms for SF-driven MEG.
• Surface functionalization offers a viable strategy to tune and enhance MEG performance in SWCNTs for solar energy applications.