Trap Passivation in Indium-Based Quantum Dots through Surface Fluorination: Mechanism and Applications

Area of Science:

• Materials Science
• Nanotechnology
• Quantum Dot Research

Background:

• Hydrofluoric acid (HF) treatment is known to improve the photoluminescence quantum yield (PLQY) of indium phosphide (InP) colloidal quantum dots (QDs).
• Previous mechanisms involved phosphorus dissolution and indium passivation by ligands after higher HF exposure.
• This study explores a different mechanism at lower HF concentrations.

Purpose of the Study:

• To investigate the mechanism of luminescence enhancement in InP QDs at lower hydrofluoric acid (HF) exposure.
• To explore the application of fluoride passivation to other indium-based QDs, such as InAs.
• To evaluate the performance of fluorinated InAs QD-based devices.

Main Methods:

• Treatment of InP colloidal quantum dots (QDs) with varying concentrations of hydrofluoric acid (HF).
• Photoluminescence quantum yield (PLQY) measurements and spectral analysis (emission and absorption peaks).
• Density functional theory (DFT) calculations to model surface interactions.
• Fabrication and characterization of fluorinated InAs QD-based electrical devices.

Main Results:

• Lower HF exposure leads to significant luminescence enhancement in InP QDs via direct passivation of surface indium dangling bonds by fluoride ions.
• This passivation causes red shifts in emission/absorption spectra and is thermodynamically favored, as shown by DFT.
• Fluorination of InAs QDs increased PLQY by an order of magnitude, and fabricated devices showed improved switching and higher mobility, eliminating persistent photoconductivity.

Conclusions:

• Surface indium passivation with fluorides is an effective strategy for enhancing QD luminescence and performance.
• This mechanism differs from previous findings at higher HF concentrations, involving direct atomic ligand passivation.
• The findings are applicable to various indium-based QDs and demonstrate improved device characteristics.