Exciton dynamics and binding energy relation in crystal-cocrystal system

Area of Science:

• Materials Science
• Quantum Chemistry
• Solid-State Physics

Background:

• Understanding light-matter interactions is crucial for developing novel electronic and optical materials.
• Crystal and cocrystal structures offer unique platforms for tuning material properties.
• Charge transfer (CT) and local excitation (LE) phenomena govern electronic behavior in condensed matter.

Purpose of the Study:

• To theoretically investigate light-matter interactions in CuCl2-4-aminoacetophenone crystal and cocrystal systems.
• To identify charge transfer pathways and analyze exciton dynamics.
• To elucidate the relationship between exciton descriptors and binding energy.

Main Methods:

• Density Functional Theory (DFT) calculations were employed for theoretical exploration.
• Natural Bond Orbital (NBO) analysis was used to study electronic interactions.
• Density of States (DOS) analysis quantified electronic state accumulation.
• Exciton descriptors (e.g., D_index, H_index, Sr, t_index) were utilized to assess exciton dynamics.

Main Results:

• Realistic charge transfer (CT) channels were identified in both crystal and cocrystal systems.
• Copper atoms form lone pair interactions and pi-conjugated pathways with ligands.
• The cocrystal exhibited a greater accumulation of electronic states compared to the parent crystal.
• Charge transfer (CT) was found to be dominant over local excitation (LE).
• Exciton binding energy decreases with increasing excitation states, with strong binding observed.

Conclusions:

• The study validates the theoretical coexistence of Frenkel-CT excitons with significant binding energy.
• Exciton descriptor values effectively illustrate exciton binding energy strength.
• The findings provide insights into the electronic and optical properties of copper-based materials for materials science applications.