(608f) Substitutional Doping in Nanocrystal Superlattice

Doping, a process in which atomic impurities are intentionally added to modify the electronic properties of a semiconductor, has revolutionized our world, making computers, transistors, detectors, solar cells and other devices possible. Artificial atoms, nanocrystals (NC) with electronic properties dictated by their size and shape, have also emerged as technologically important materials. In this contribution, we introduce the concept of nanocrystal (NC) doping by merging the two above mentioned concepts. We show that, by matching the size of monodisperse gold nanocrystals (Au NCs) with that of semiconducting nanocrystals of cadmium selenide (CdSe) or lead selenide (PbSe) quantum dots (QDs), it is possible to purposely dope the semiconductor superlattices and induce novel properties in these self-assembled materials. We demonstrate that, comparably to the case of atomic doping, the Au NCs take random positions in the superlattice and their concentration can be tuned over a wide range. We show that the electronic and optical properties of the superlattices are affected by the presence of the Au dopants, which increase the conductivity and the photoconductivity of bare CdSe films by several orders of magnitude. We anticipate that this approach can originate a wide variety of NC-doped structures with applications in several fields including electronic materials, solar cells, sensors and catalysis.