Auger Recombination Lifetime Scaling for Type-I and Quasi-Type-II Core/Shell Quantum Dots

Abstract

Having already achieved near-unity quantum yields, with promising properties for light-emitting diode, lasing, and charge separation applications, colloidal core/shell quantum dots have great technological potential. The shell thickness and band alignment of the shell and core materials are known to influence the efficiency of these devices. In many such applications, a key to improving the efficiency requires a deep understanding of multiexcitonic states. Herein, we elucidate the shell thickness and band alignment dependencies of the biexciton Auger recombination lifetime for quasi-type-II CdSe/CdS and type-I CdSe/ZnS core/shell quantum dots. We find that the biexciton Auger recombination lifetime increases with the total nanocrystal volume for quasi-type-II CdSe/CdS core/shell quantum dots and is independent of the shell thickness for type-I CdSe/ZnS core/shell quantum dots. In order to perform these calculations and compute Auger recombination lifetimes, we developed a low-scaling approach based on the stochastic resolution of identity. The numerical approach provided a framework to study the scaling of the biexciton Auger recombination lifetimes in terms of the shell thickness dependencies of the exciton radii, Coulomb couplings, and density of final states in quasi-type-II CdSe/CdS and type-I CdSe/ZnS core/shell quantum dots.