Over the last few years organic semiconductors have seen a dramatic rise in interest from both academia and industry alike. This has been largely due to their promise of low-cost, high-throughput manufacture, combined with many other positive attributes including their: flexibility; semi-transparency and light-weight nature. This combination of factors show that organic semiconductors hold strong potential to compete with inorganic technologies in a number of existing and emerging applications. More specifically, blends comprised of a number organic semiconductors offer significant promise for devices such as organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs), as tuning the chemical nature of the constituting materials can influence the blend’s optoelectronic properties. However, during processing, such as blending, complex mixture of phases are formed which renders understanding these systems challenging.
This thesis examines the relationships between the three critical aspects that affect organic semiconducting blends, namely: the processing route selected, the resulting microstructure and, as a consequence, the induced optoelectronic properties. A more comprehensive understanding is developed of how the processing route (solution casting from common solvent vs. bilayer fabrication via lamination) can affect the structural formation processes in organic semiconductor systems, such as crystallisation, vitrification etc. Additionally, this thesis elucidates how the structural formation processes influence the mixture of phases that evolve and discusses how the microstructure that is created affects the photo-physical processes such as exciton quenching and charge generation, within these systems.
The results within this thesis highlight the sensitive interplay between the three areas of structure, property and processing. Clear insights into how to manipulate these aspects to positively impact the photo-physical processes are conferred. The findings discussed here give, thus, clear guidelines as to how to further enhance understanding and terminally improve the performance of devices such as organic solar cells.