The effect of functionalisation on thermoelectric properties of molecular junctions

To better understand and develop new organic thermoelectric materials, a bottom-up approach of using molecular electronics consisting of scattering regions such as organic molecules connected between two gold electrodes was used. In the beginning of this thesis, an in-depth introduction to the history of quantum mechanics, the state-of-the-art inorganic/organic thermoelectric materials, and recent development of molecular electronics is provided. Then, a comprehensive explanation of various mathematical and computational methods that served as the backbone of all of the later theoretical investigations is outlined. Three distinct molecular junction design strategies are used to tune the quantum interference (QI) behaviours in order to find out which molecules have good potential quantum transport, electrical and thermoelectric properties such as transmission coefficient (T(E)), electrical conductance (G), Seebeck coefficient (S ), and power factor (PF). The first strategy is to incorporate various heteroatoms into polycyclic aromatic hydrocarbons (PAHs). The second strategy is then to use multiple types of anchor groups within the junction, instead of the conventional singular type. Finally, the third strategy is to employ a donor–acceptor–donor (DAD) architecture to find out what benefits it brings. In total, a total of five novel investigations are carried out and discussed in the span of two results chapters. The ultimate goal of this thesis is to progress in the development of thermoelectric materials, which has been successful since several new molecular junctions have been identified as having excellent S and PF simultaneously.