Publication date: 17th July 2025
II-VI and III-V core-only colloidal quantum dots (QDs) often suffer from surface defects that create deep trap states, severely limiting photoluminescence efficiency and device performance. These traps typically originate from undercoordinated anions at anion-rich facets, promoting non-radiative recombination. While surface passivation strategies can help, achieving complete and stable passivation remains challenging and highly material-dependent. Core@shell architectures provide an alternative by isolating the optically active core, but can introduce new complications at the core-shell interface. In particular, core@shell systems combining materials from different families, such as III-V@II-VI heterostructures commonly used to shell III-V QDs, face charge imbalances due to bonding differences and lattice mismatch, which can in turn create interfacial traps.
To address these challenges, we present a computational framework based on density functional theory and Bader charge analysis to investigate how covalency and ionicity together influence the energetic positions of molecular orbitals (MOs) at the valence and conduction band edges. Using InAs as a reference core QD model, we compare combinations of zinc-blende materials used as shells from both III-V and II-VI families. We examine the impact of different facets on the electronic structure, focusing on the emergence of facet-specific, localized trap states at these interfaces. Our analysis breaks down the contributions of covalency and ionicity to MO stability, providing guidance for the design of more robust and efficient QD heterostructures.
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