Locally Doped Nanorods: Introducing Distance-Dependence in Excitonic Nanostructures

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In this project we aim to synthesise semiconductor nanorods that contain transition metal dopants localised to a specific region along the rod. Semiconductor nanocrystals are attractive materials to be used for energy harvesting and conversion in e.g. solar cells, lasers, and photonics. Apart from the well-understood size quantisation effect, which allows to tune optical and electronic properties of nanocrystals by controlling their size and shape, doping with impurity ions is an increasingly important method to manufacture functional nanomaterials. Transition metals, especially paramagnetic ions, are suitable dopants, because they can be detected by their magnetic moment and size-independent fluorescence. Trapping of excited charge carriers on dopants occurs extremely fast, which so far has hampered observation of the charge transfer process in doped nanocrystals. We propose a 1D structure in which a doped region of the semiconductor material is separated from a second recombination centre for charge carriers (e.g. a heterojunction) by the length of the nanorod. This will allow us to spatially decouple the dopant-related processes from excitation and charge recombination and hence elucidate the fundamental carrier dynamics at very short times after photon absorption. This project will introduce distance as a new dimension of control over doping-related processes in semiconductor nanoparticles and help to design and fabricate doped nanoparticles with control over dopant distribution beyond the current state of the art. The results will be highly relevant for energy materials and photovoltaics, spintronics, and new fluorophores.