Identity of the reversible hole traps in InP/ZnSe core/shell quantum dots

Area of Science:

• Materials Science
• Quantum Dot Research
• Solid-State Physics

Background:

• Quantum dots (QDs) are crucial in optoelectronics, but defects can limit their performance.
• Reversible hole trapping in InP/ZnSe/ZnS QDs affects their photoluminescence properties.
• Understanding defect sites is key to improving QD stability and efficiency.

Purpose of the Study:

• To identify the specific defect responsible for reversible hole trapping in InP/ZnSe/ZnS QDs.
• To correlate experimental observations with theoretical calculations for defect identification.
• To elucidate the mechanism of hole trapping and its impact on QD behavior.

Main Methods:

• Combined density functional theory (DFT) calculations with time-resolved photoluminescence experiments.
• Investigated excess indium in the shell of InP/ZnSe/ZnS QDs.
• Analyzed the effect of additives like zinc oleate, acetate, and carboxylic acids on trapping.

Main Results:

• Identified a substitutional indium adjacent to a zinc vacancy (In³⁺/V_Zn²⁻) as the most likely hole trapping species.
• Demonstrated that excess indium is necessary for trapping, and its extent is modulated by additives.
• Calculations showed this defect's energy levels are suitable for trapping quantum-confined holes.

Conclusions:

• The In³⁺/V_Zn²⁻ defect is the primary cause of reversible hole trapping in these QDs.
• This finding provides critical insights into defect engineering for enhanced QD performance.
• The study clarifies the role of specific atomic configurations in QD photophysics.