Theoretical investigation of toxic-metal-free nanocrystals for technological applications

Lead Research Organisation: University of Leeds
Department Name: Electronic and Electrical Engineering

Abstract

Context of research:
Nanotechnology centers around the ability to engineer materials at the nanoscale (that is, to manipulate structures with typical dimensions of the order of 1/100,000 of the thickness of a human hair), for technological applications. Colloidal quantum dots (QDs, aka nanocrystals, NCs) are chemically synthesised single-crystalline spherical semiconductor nanostructures with typical dimensions of a few nanometers which exhibit several characteristics that make them attractive for this field: (i) their size-tunable optical properties enable their application in very different fields such as optoelectronics (in lasers and LEDs), as well as biology and medicine (as organic molecule markers), and PV, allowing their absorption energies to be tailored to maximise solar photon absorption; (ii) their colloidal (i.e., chemical) nature enables low cost and large scale production; (iii) the very high degree of size monodispersity (less than 5%) achievable in their synthesis provides reproducibility and growth control. These properties make them also compatible with existing fibre-optic technologies and useful as building blocks for bottom-up assembly of various optical and electronic devices, including optical amplifiers, lasers and single-electron transistors. However, most of the nanocrystals exploited in such applications are made of Cd- and Pb-based materials (i.e., of CdX and PbX, where X=S, Se, Te), which are highly toxic for humans and the environment. It is therefore paramount to find non-toxic alternatives that can represent viable substitutes to such well characterised and well performing materials.
This is the aim of this project.

Aims and objectives:
To apply the atomistic semiempirical pseudopotential method (SEPM) developed in the Solid State Theory group at the National Renewable Energy Lab, Golden (CO) U.S.A., to theoretically screen different ("novel" and more conventional) Cd- and Pb-free colloidal materials and alternative topological structures for technological applications at the nanoscale, ranging from PV to nanoelectronics. Possible materials include Ga- and In- based ones (i.e., GaX and InX, where X=As, Sb and P), whereas possible structures include rods and tetrapods (potentially better suited for transport in films), as well as spherical nanocrystals.

Potential applications and benefits:
One of the many possible implications of the study on tetrapods of different materiasl could be the enhancement of miniband formation and transport in QD films, with applications ranging from PV to nanoelectronics (transistors). Others could involve the design of novel biosensors exploiting the long carrier lifetimes in Ga-based materials.
Furthermore, the student will develop a deep knowledge and competence in the use of a state-of-the-art theoretical modelling method and, through collaborations with national and international experimental groups and attendance to conferences, will start building a network of collaborators.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509681/1 01/10/2016 30/09/2021
2037499 Studentship EP/N509681/1 01/09/2017 28/02/2021 Panagiotis Rodosthenous