Competition among recombination pathways in single FAPbBr3 nanocrystals

Area of Science:

• Materials Science
• Nanotechnology
• Photophysics

Background:

• Photoluminescence (PL) intermittency in nanocrystals (NCs) is crucial for understanding their optical properties.
• Investigating single NCs reveals complex blinking behaviors and underlying mechanisms.

Purpose of the Study:

• To elucidate the processes governing photoluminescence intermittency in FAPbBr3 NCs at the single-particle level.
• To analyze blinking patterns and their dependence on excitation conditions.

Main Methods:

• Single-particle level microscopy of immobilized FAPbBr3 NCs.
• Fluorescence Lifetime Intensity Distribution (FLID) analysis.
• Change-Point Analysis (CPA) and probability distribution analysis of PL trajectories.
• Investigation across different excitation fluences and wavelengths (400 nm, 440 nm).

Main Results:

• Observed four distinct photoluminescence blinking patterns across over 100 NCs.
• FLID plots revealed interplay of exciton, trion, and hot carrier (HC) trapping.
• Neutral excitons, trions, and hot carriers contribute to different PL intensity-lifetime components.
• Truncated power law distribution better describes on/off events than power law or lognormal.
• Trapping rate (kT) dominates at higher power densities for both excitation wavelengths.

Conclusions:

• Multiple intermediate states are involved in PL intermittency, as shown by CPA.
• Competition exists between hot carrier and trion-assisted blinking pathways.
• The relative contribution of these mechanisms is modulated by excitation wavelength and fluence.