Microscopic Theory of Cation Exchange in CdSe Nanocrystals

TL;DR

This paper develops a microscopic theory using DFT and kinetic Monte Carlo simulations to explain how Coulomb interactions influence cation exchange in CdSe nanocrystals, clarifying experimental observations.

Contribution

It introduces a detailed microscopic model that explains structural, optical, and electronic changes during cation exchange in CdSe nanocrystals, emphasizing Coulomb interactions.

Findings

Coulomb interactions are crucial in cation exchange processes.

The theory explains photoluminescence and electrical behavior puzzles.

Simulations match experimental observations of Ag-cation-exchanged CdSe nanocrystals.

Abstract

Although poorly understood, cation-exchange reactions are increasingly used to dope or transform colloidal semiconductor nanocrystals (quantum dots). We used density-functional theory and kinetic Monte Carlo simulations to develop a microscopic theory that explains structural, optical, and electronic changes observed experimentally in Ag-cation-exchanged CdSe nanocrystals. We find that Coulomb interactions, both between ionized impurities and with the polarized nanocrystal surface, play a key role in cation exchange. Our theory also resolves several experimental puzzles related to photoluminescence and electrical behavior in CdSe nanocrystals doped with Ag.