First-Principles Calculations of Luminescence Spectra of Real-Scale Quantum Dots

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Chemistry

Background:

• Semiconductor quantum dots (QDs) are crucial for optical applications, with luminescence line shape significantly impacting performance.
• Predicting the luminescence spectrum of large QDs (thousands of atoms) remains a challenge.

Purpose of the Study:

• To develop a first-principles method for accurately predicting the luminescence spectrum of large semiconductor quantum dots.
• To elucidate the role of exciton-phonon coupling (EPC) in determining QD spectral line shapes.
• To provide guidelines for designing high-performance core/shell QDs with ultrasharp emission spectra.

Main Methods:

• Combined neural network potential calculations with density functional theory (DFT) to model exciton-phonon coupling (EPC).
• Evaluated luminescence spectra using the Franck-Condon approximation based on calculated EPC.
• Applied the method to a large InP/ZnSe core/shell quantum dot (3406 atoms).

Main Results:

• Achieved excellent agreement between predicted and experimental luminescence line shapes for a large core/shell QD.
• Revealed that coupling to both acoustic and optical phonons is critical for spectral line shapes in core/shell QDs.
• Identified key factors influencing spectral line shapes, contrasting with previous studies.

Conclusions:

• The developed first-principles method accurately predicts luminescence spectra for large QDs.
• A comprehensive understanding of EPC is essential for controlling QD optical properties.
• The findings offer a pathway for designing advanced core/shell QDs with tailored, sharp emission characteristics.