Excimer Formation in the Non-Van-Der-Waals 2D Semiconductor Bi₂ O₂ Se.

Area of Science:

• Materials Science
• Condensed Matter Physics
• 2D Materials

Background:

• Bismuth oxyselenide (Bi2O2Se) is a novel layered semiconductor with electrostatic interlayer forces, distinct from van der Waals interactions.
• Its non-van der Waals nature and inherent electric field offer a unique platform for studying photoexcited carrier dynamics.

Purpose of the Study:

• To experimentally investigate the dynamics of photoexcited excitons in multilayer Bi2O2Se nanosheets.
• To identify and characterize the presence and behavior of excimers in this material.

Main Methods:

• Transient absorption spectroscopy was employed to probe the photoexcited carrier dynamics.
• Excitation-fluence-dependent measurements were conducted to understand excimer formation mechanisms.

Main Results:

• Experimental evidence confirmed the observation of excimers in multilayer Bi2O2Se nanosheets.
• Excimer formation was identified as the primary decay pathway for photoexcited excitons.
• A three-stage excimer dynamic with distinct time scales was established, indicating diffusive behavior.

Conclusions:

• The study reveals that excitons in Bi2O2Se relax into an excimer geometry, a process that can be simply described.
• The unique excitonic processes in Bi2O2Se highlight its potential for novel device applications.
• This research underscores the significance of non-van der Waals 2D materials in exploring fundamental photophysics.