Quantum Confinement Theory of Auger-Assisted Biexciton Recombination Dynamics in Type-I and Quasi Type-II Quantum Dots

Abstract

Use of quantum confinement as a tool to control biexciton recombination in quantum dots is investigated theoretically for a series of quasi-Type-II and Type-I CdSe/CdS core/shell spherical quantum dots. Recent experimental measurements show that in such nanostructures, the CdS shell may act as a type of an efficient retarder for biexciton recombination in the quasi-Type-II regime, but not as efficient in the Type-I regime, and that this phenomenon is achieved by a strong charge separation in the former. These findings are interpreted on the basis of Auger-assisted biexciton decay using a quantum confinement theory. We perform single-band effective mass calculations simulating the quasi-Type-II regime by a CdSe 2.4 nm core + CdS shell and the Type-I by a CdSe 3.8 nm core + CdS shell. The calculations reveal a tightly confined hole for both types of regimes. The key difference occurs in the behavior of the electron, whose wavefunction is progressively delocalized into the growing shell region in the quasi-T...