Nanorod Heterostructures Showing Photoinduced Charge Separation

Graphical Abstract

Supramolecular analogs of donor–acceptor pairs in nanorod heterostructures are reported. The charge-transfer band position and respective photoluminescence decay times depend on the segmental nanorod dimensions (see image). A PL lifetime almost an order of magnitude higher than the respective band-edge emissions of constituting nanorods is measured.

Abstract

Size- and shape-dependent property modifications of semiconductor nanocrystals have been a subject of intense interest because of their potential for future engineering devices. The bandgap and related optical-property tuning of these materials are mainly governed by the nature of their band edges. In addition, fusing one type of nanocrystal over another enables further control of material properties that are dependent on the relative alignments of their energy levels. On a molecular scale, the synthesis of supramolecular compounds has inspired advances in theories for photoinduced charge transfer. Heterostructured nanocrystals potentially provide a nanoscale analog of such systems. A method for preparing heterostructured nanocrystals of complex morphologies showing photoinduced charge separation is presented. It is shown that the energy and lifetime of the charge-transfer photoluminescence band can be tuned by changing the relative alignment of band edges in CdSe/CdTe heterostructure nanorods. The long-lived charge transfer states in these type II semiconductors may make them attractive for photovoltaic applications.