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Title: Electronic structure simulations of energy materials : chalcogenides for thermoelectrics and metal-organic frameworks for photocatalysis
Author: Aziz, Alex
ISNI:       0000 0004 7233 5838
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2018
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A theoretical investigation of the electronic structure of chalcogenides for thermoelectric applications and metal organic frameworks (MOFs) for photocatalytic applications is presented in this thesis. The development of chalcogenide materials for thermoelectric applications presents an opportunity to move away from tellurium based materials, which are not cost-effective. Their mainstream realization is dependent on an increase in their efficiency. A combination of density functional theory and Boltzmann transport theory are used to investigate the electronic and phonon transport properties of chalcogenide materials. In the shandite family, the transport properties of Ni3Sn2S2 provide a useful rationalization of their behaviour. In Co3Sn2S2 indium substitutes tin preferentially at the interlayer sites, and leads to a compositionally induced metal-tosemiconductor-to-metal transition which is critical to its thermoelectric properties. Cu2ZnSnSe4 is the most promising of the quaternary chalcogenides and is investigated for thermoelectric applications. It is a p-type semiconductor and a combined theoretical and experimental analysis shows how its ZT can be optimized through doping. In the second part of this thesis, two classes of MOFs are investigated for their photocatalytic properties, porphyrin based MOFs (PMOFs) and zeolitic imidazolate frameworks (ZIFs). In both materials, DFT calculations are used to obtain the electronic band structure, which is then aligned with a vacuum reference. In these MOFs, as in chalcogenides, chemical substitution can be used to engineer the band structure for their optimal properties. In PMOFs metal substitution at the octahedral metal centre is able tune the band edge positions. Optimal properties were found by partial substitution of Al by Fe at the octahedral sites, while keeping Zn at the porphyrin centres. In ZIFs the band edge positions are mainly determined by the molecular linker and intrinsic photocatalytic activity can be achieved by mixing different linkers.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral