Charge and energy transfer in the context of colloidal nanocrystals

As the number of hybrid systems comprising quantum-confined semiconductor nanocrystals and molecules continues to grow, so does the need to accurately describe interfacial energy and charge transfer in these systems. The earliest work often successfully captured at least qualitative trends in the rates of these processes using well-known results from Forster, Dexter, and Marcus theories, but recent studies have showcased how unique properties of nanocrystals drive interfacial energy transfer (EnT) and charge transfer (CT) to diverge from familiar trends. This review first describes how the nanocrystal-ligand system fits, at least superficially, into conventional models for EnT and CT, and then gradually introduces individual properties of nanocrystals that complicate our understanding of EnT and CT mechanisms. The review then explores instances in which features of nanocrystals that seem detrimental, such as trap states that introduce non-radiative recombination pathways and strong spin-orbit coupling, can be controlled or used synergistically to produce a wider range of functionality than available in all-molecular donor-acceptor systems.