3D naphthalene and perylene diimide derivatives as non-fullerene acceptors for organic solar cells
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Non-fullerene acceptor (NFA) have great potential to replace fullerene materials and overcome their limitations such as relatively weak light absorption, poor morphological stability, and synthetic complexity of introducing structural diversity to fine tune energy levels. A series of naphthalene and perylene diimide (NDI and PDI, respectively) based 3D-shaped non-fullerene acceptors were synthesized and their optical and electronic properties were studied as described in this thesis. Chapter 2 focuses on four NDI-based NFAs with different non-planar central core units. It was found that these materials have broader absorptions compared to typical fullerenes, and the strong tendency of planar NDIs to aggregate was hindered by the non-planar structure that arises when four naphthalene diimides are connected to a core. These materials have comparable estimated reduction potentials to PC61BM, and exhibit multi-electron reductions. Upon blending with a low optical gap crystalline donor polymer, these materials are electron acceptors and produce average device efficiencies, specifically PCEs, between 1.3-2.6 %. In chapter 3, an analogue of the best performing NFA in chapter 2 was synthesized in which NDIs were replaced by PDIs. These PDI-based NFAs have broader and stronger light absorptions in the visible region of the spectrum in comparison with NDI analogs, while maintaining similar electrochemical properties. Device fabrication and optimizations of these PDI materials is ongoing.