ABSTRACT
Semiconductor nanocrystals (NCs) are nanometer-sized crystalline particles that contain approximately 100 to 10,000 atoms. The ability to precisely control the composition, size, and shape of NCs provides great flexibility in engineering their electronic and optical properties by directly manipulating electronic wave functions. This chapter focuses on carrier relaxation behaviors in the context of the optical gain properties of NCs and their potential applications in lasing technologies. It contains a more general overview of multiexciton phenomena in nanocrystalline materials. The chapter starts with a brief discussion of the structure of electronic states in NCs and the spectroscopic signatures of multiexcitons in transient absorption and photoluminescence. It reviews the work on single-exciton and multiexciton dynamics, including the dependence of multiexciton Auger lifetimes on NC size and exciton multiplicity, the comparison of Auger decay dynamics in NCs of direct- and indirect-gap semiconductors, and the dependence of Auger recombination rates on the energy gap tuned by hydrostatic pressure.
