Locality of conical intersections in semiconductor nanomaterials

Area of Science:

• Materials Science
• Quantum Chemistry
• Solid-State Physics

Background:

• Designing semiconductor nanomaterials for optoelectronics requires understanding electron recombination rates.
• Theoretical studies of conical intersections offer a pathway to predict these rates based on atomic structure.

Purpose of the Study:

• To review recent work on conical intersections in nanomaterials.
• To establish and illustrate the concept of 'locality' in low-energy conical intersections.
• To explore the implications of locality for predicting and controlling recombination.

Main Methods:

• Theoretical study of conical intersections.
• Analysis of electron excitation between localized orbitals.
• Investigation of geometric distortions influencing orbital energies.
• Case studies on silicon defects and silicon nanocrystals.

Main Results:

• Low-energy conical intersections in nanomaterials are characterized by locality.
• Locality is defined by spatially localized orbitals and geometry-tuned orbital energies.
• Demonstrated locality in silicon with dangling bond defects, pristine silicon nanocrystals, and systems with multiple defects.
• The lowest energy intersection in a two-defect system localized to a single defect.

Conclusions:

• The locality of conical intersections is a common feature in nanomaterials.
• This locality has significant implications for predicting electron recombination rates.
• Exploiting locality could enable experimental studies using molecular models for new insights into recombination processes.