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
