Organic semiconductors have several advantages over their inorganic counterparts. For example, the solution processability allows for the fabrication of flexible, lightweight and low-cost semiconducting devices. However, much work is needed to compete with the high-performance of inorganics.
The first half of this work focuses primarily on nucleophilic aromatic substitution (SNAr) reactions with molecules and polymers containing the fluorinated 2,1,3-benzothiadiazole (BT) unit. Chapter 2 explores the effect the type of heteroatom on the BT unit (N, O and S) of a carbazole-based polymer has on the optical properties and organic photovoltaic (OPV) performance. The following chapter focuses on post-polymerisation SNAr reactions, in which thiols were found to displace fluorine groups on a variety of polymers, including polymers containing fluorinated benzotriazole (BTz) and thienothiophene (TT) units instead of BT. The reaction was then taken a step further, by substituting fluorine atoms on P(F8fBT) with a diverse range of end-functionalised thiols, thioacetates and alcohols. It was also found that the amount of thiol substitution could be finely tuned, which led to the development of multifunctionalised polymers.
The second half of this thesis explores the possible applications of the BT SNAr reaction towards semiconducting polymer nanoparticles (SPN) and OPVs. In Chapter 4, SPNs from polymers functionalised with azide and carboxylic groups were synthesised and the surface was found to be reactive to strained-alkynes and amines, respectively. In the final chapter, a trimethoxysilane-functionalised OPV polymer was synthesised and was found to increase the thermal stability of devices via cross-linking, with no additives required.