The Electronic Structure of CdSe/CdS Core/Shell Seeded Nanorods: Type-I or Quasi-Type-II?

TL;DR

This study investigates the electronic structure of CdSe/CdS core/shell nanorods, revealing how core size influences the transition between type-I and quasi-type-II band alignments, primarily driven by volume effects rather than band alignment changes.

Contribution

The paper demonstrates that the transition from type-II to type-I in CdSe/CdS nanorods is mainly due to volume effects, providing new insights into their electronic structure.

Findings

Hole localized in the core regardless of size

Core-overlap varies with core size, affecting band type

Electron-hole interactions increase core-overlap

Abstract

The electronic structure of CdSe/CdS core/shell seeded nanorods of experimentally relevant size is studied using a combination of molecular dynamics and semiempirical pseudopotential techniques, with the aim to address the transition from type-I to a quasi-type-II band alignment. The hole is found to be localized in the core region regardless of its size. The overlap of the electron density with the core region depends markedly on the size of the CdSe core: For small cores, we observe little overlap, consistent with type-II behavior. For large cores, significant core-overlap of a number of excitonic states can lead to type-I behavior. When electron-hole interactions are taken into account, the core-overlap is further increased. Our calculations indicate that the observed transition from type-II to type-I is largely due to simple volume effects, and not to band alignment.