Conjugated Macrocycles in Organic Electronics

The discipline of organic electronics encompasses the design and synthesis of molecules for use in organic field effect transistors, organic photovoltaics, organic photodetectors, single molecule electronics, sensors, and many more. The rationale for studying organic electronic materials is compelling: organics have the potential to be low cost, processable, and flexible complements to silicon technologies to combat some of the most pressing environmental issues. Organic molecules that transport carriers are used as the active layer in many device applications. Molecules that possess energy levels that allow for electron or hole transport are typically π-conjugated materials. There has been swift progress on the design and synthesis of π-conjugated materials that possess a large density of high energy electrons such as acenes. Yet there has been less growth on materials with low energy vacant orbitals to accept an electron. Fullerenes are the ubiquitous acceptor materials used in organic electronics. Over the past few years, there have been several groups, including our own, that have synthesized non-fullerene materials for use in organic field effect transistors and solar cells. In particular, the Nuckolls laboratory has pioneered the design and synthesis of a class of molecules called contorted aromatics and studied these molecules in range of organic electronic applications. Conjugated macrocycles are one sub-class of the contorted aromatic family. This Thesis describes a body of research on the design, synthesis, and application of a new class of electronic materials made from conjugated macrocycles. Each of the macrocycles comprises perylenediimide cores wound together with various electronic linkers. The perylenediimide building block endows each macrocycle with the ability to transport electrons, while the synthetic flexibility to install different linkers allows us to create macrocycles with different electronic and physical properties. We use these materials in organic photovoltaics, field effect transistors, sensors, and photodetectors. The macrocycles possess vivid colors, absorb in the visible range of the solar spectrum, and are an exemplary class of materials to study how rigidity and strain affect device performance. We find that the strained and rigid macrocyclic framework affords each macrocycle with the ability to absorb lower energy visible light with respect to acyclic counterparts and the macrocycles outperform in photovoltaic applications. Rigidity was an important concept in our organic photodetector study: we found rigidity was one of the reasons our macrocycles outperformed both fullerenes and acyclic controls. The macrocycles all possess intramolecular cavities, and our recent studies focused on using this nanospace for sensing applications. Each of the studies described in this Thesis will demonstrate how macrocyclization is a design technique to enhance organic electronic performance