Exciton Transport and Interfacial Charge Transfer in Semiconductor Nanocrystals and Heterostructures

Quantum confined semiconductor nanocrystals (NCs), in particular, zero-dimensional (0D) quantum dots, one-dimensional (1D) nanorods, and two-dimensional (2D) nanoplatelets, possess properties that differ significantly from their bulk counterparts and have been widely used as light harvesting and charge separation materials in photocatalytic applications, such as light-driven H2 generation. An efficient NC-based photocatalytic system requires both efficient exciton dissociation by charge transfer from NCs to adsorbed acceptors or catalysts and slow charge recombination. This chapter provides a review of recent studies of fundamental exciton and carrier dynamics in cadmium chalcogenide NCs and their effects on the light-driven H2 generation performances. The review starts with an introduction of the electronic structure of 0D-2D NCs, the band alignments of NC heterojunction or interfaces, and the exciton transport behaviors of 1D and 2D NCs. It is followed by a discussion of the mechanisms of single exciton dissociation, multi-exciton Auger recombination, and multi-electron transfer from NCs. The charge separation and recombination properties in NC-metal heterostructures and their light-driven H2 generation performances are summarized. The chapter concludes by discussing key remaining challenges for efficient solar-to-H2 conversion using colloidal quantum confined nanostructures.