Multicarrier Dynamics in Quantum Dots

Multicarrier dynamics play an essential role in quantum dot photophysics and photochemistry, and they are primarily governed by nonradiative Auger processes. Auger recombination affects the performance of lasers, light-emitting diodes, and photodetectors, and it has been implicated in fluorescence intermittency phenomena which are relevant in microscopy and biological tagging. Auger cooling is an important mechanism of rapid electron thermalization. Inverse Auger recombination, known as impact ionization, results in carrier multiplication which can enhance the efficiencies of solar cells. This article first reviews the physical picture, theoretical framework and experimental data for Auger processes in bulk crystalline semiconductors. With this context these aspects are then reexamined for nanocrystal quantum dots, and we first consider fundamental features of Auger recombination in these systems. Methods for the chemical control of Auger recombination and Auger cooling are then discussed in the context of how they illuminate the underlying mechanisms, and we also examine the current understanding of carrier multiplication in quantum dots. Manifestations of Auger recombination in quantum dot devices are finally considered, and we conclude the article with a perspective on remaining unknowns in quantum dot multicarrier physics.