Band Alignment in Core-Shell Nanocrystals by Estimating Wave Function Tunneling Probabilities

Area of Science:

• Materials Science
• Quantum Chemistry
• Nanotechnology

Background:

• Core-shell colloidal semiconducting nanocrystals (NCs) offer significant optoelectronic potential.
• Complex interfaces in NCs complicate the quantification of electron and hole confinement and band offsets.
• Existing theoretical and experimental methods face challenges in accurately characterizing these properties.

Purpose of the Study:

• To develop a reliable and user-friendly density functional theory (DFT)-based approach for estimating wave function tunneling probabilities in core-shell NCs.
• To quantify electron and hole confinement and band offsets in II-VI core-shell heterostructures.
• To investigate the factors influencing level alignment and wave function delocalization.

Main Methods:

• Utilized a novel DFT-based approach for first-principle atomistic simulations.
• Estimated wave function tunneling probabilities between core and shell materials.
• Investigated electron/hole confinement in Type-I, Type-II, and quasi-Type-II II-VI core-shell nanocrystal heterostructures.

Main Results:

• Band offsets in different heterostructure types qualitatively align with bulk trends.
• Quantitative level alignment is sensitive to lattice match, nanocrystal shape, and shell thickness.
• Significant wave function tunneling of electrons and holes across the core-shell interface was observed.

Conclusions:

• The developed DFT approach provides a reliable method for assessing confinement in core-shell NCs.
• Wave function tunneling across interfaces is substantial and must be considered for effective passivation.
• Findings have implications for designing and optimizing core-shell heterostructures for optoelectronic applications.