This thesis is focused on applying direct heteroarylation as an efficient and sustainable synthetic route to access high-performance pi-conjugated molecular materials for use as non-fullerene acceptors as part of the active layer component of organic solar cells. Chapter One introduces pi-conjugated materials, organic solar cells and the importance of developing sustainable and efficient methods to access high-performance materials. In Chapter Two, the discussion is focused on the optimization

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... f cross-coupling reactions catalyzed by a robust and reusable silica-supported palladium catalyst for the synthesis of pi-conjugated materials (SM-1–3) following both traditional Stille or Suzuki couplings and highlighting the advantages of direct heteroarylation over these methods. Chapter Three focuses on expanding the substrate scope to more complicated building blocks, while also comparing direct heteroarylation to Sonogashira couplings and their respective influences on synthetic accessibility and optoelectronic properties (SM-4–5). Chapter Four applies the synthetic methods developed in Chapters Two and Three and extends these principles to the design and synthesis of a non-fullerene acceptor based on the organic dye isoindigo (SM-6). Chapter Five is a direct follow-up on the derivatization of the parent compound disclosed in Chapter Four and how synthetic modification through the versatile direct heteroarylation coupling can lead to improved device performance (SM-7–9). Chapter Six is focused on identify the most promising organic dye core structure to include between flanking perylene diimide units, an extension of previous designs utilizing isoindigo and phthalimide-flanking units (SM-10–14). Chapter Seven follows the optimization of the most promising non-fullerene acceptor from Chapter Six, with a diketopyrrolopyrrole dye core (SM-13), which was able to achieve a high power conversion efficiency of 5.6 %, which is among the best in its class. Chapter Eight explores a series of scalable donor materials that were [...]