Dynamics of recombination via conical intersection in a semiconductor nanocrystal

Area of Science:

• Materials Science
• Quantum Chemistry
• Nanotechnology

Background:

• Conical intersections are known to facilitate nonradiative decay in molecules.
• Their role in nonradiative recombination in materials is a recent area of investigation.

Purpose of the Study:

• To investigate nonradiative recombination pathways in defective silicon nanocrystals.
• To identify the role of dangling bond defects in these processes.

Main Methods:

• Excited-state *ab initio* molecular dynamics simulations.
• Multireference electronic structure calculations.
• Simulations performed on silicon nanocrystals (up to 1.7 nm) with dangling bond defects.

Main Results:

• Dangling bond defects induce conical intersections between ground and excited electronic states.
• These defect-induced conical intersections are accessible at visible light energies (2.4-2.7 eV).
• Ultrafast recombination (40-60 fs) occurs due to Jahn-Teller distortion driving the system towards conical intersections.

Conclusions:

• Defective silicon nanocrystals possess accessible, ultrafast nonradiative recombination pathways.
• Dangling bonds are key to enabling these pathways via defect-induced conical intersections.
• This finding has implications for understanding energy dissipation in nanomaterials.