Abstract: 

The field of molecular electronics is an interdisciplinary field that includes physics, materials science, chemistry and engineering, where small molecules serve as the basis for electronic components. The large potential of molecular devices stem from their self-assembled device structures and excellent chemical diversity; offering unrivaled cost-efficiency at nanoscales with extensive scalability for many different devices with novel applications. The commonly used metal/molecule/metal device structure also offers excellent testing platforms for investigating charge transport mechanisms in organic molecules and at molecule-electrode interfaces. 

The material contained in this dissertation focuses on furthering the understanding of the fundamental charge transport mechanisms in one of the simplest molecular devices: the molecular rectifier. We explore novel methodologies to enhance electrical performance as well as to diversify functionality. This work encompasses the usage of novel organic materials and spans from device design to characterization to the development of new theoretical models. Specifically, we focus on utilizing devices based on molecular rectifiers for the novel application of sensing humidity both reproducibly and reversibly over a wide humidity range. Additionally, we improve the modeling of molecular rectification mechanisms in molecular ensemble junctions by including the often overlooked Stark effect as well as treating the number of conducting molecules in the junction as a function of bias. We also introduce a method of enhancing rectification by exploiting new electronic states within mixed self-assembled monolayers through a novel process of intermolecular charge transfer. Lastly, we investigate the temperature dependencies of charge transport in these devices, highlighting the intricacies of coherent and incoherent tunneling mechanisms and bringing forth evidence that entropic effects on molecular configurations contribute to high-performance molecular rectification. In summary, we expand the knowledge of the design, operation, and utility of molecular rectifiers.

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