Exploring Structure-Property Relationships in Conjugated Organic Materials
In order to accelerate independence from fossil fuels, it is imperative to develop clean and renewable energy sources that can support increasing worldwide demands. Conjugated organic polymers and oligomers can be used as materials in organic photovoltaic (OPV) devices, also known as organic solar cells, which convert sunlight into electricity. In contrast to currently available inorganic solar cells, these devices are promising because of low cost, ease of manufacturing, and flexibility of the resulting solar cell. However, current OPV devices are not efficient enough to compete with inorganic cells, and a significant cause of the lagging efficiency of OPV devices is the inability to design them using theoretical methods.
This dissertation describes the development and initial groundwork of a new computational methodology to predict the device properties and efficiency of any oligomer-based OPV device from only the molecular structure of the materials that make it up. Chapter 1 provides an introduction to the problems facing this work, and Chapter 2 describes the methodology in detail. The methodology is multiscale; it takes place at the molecular scale where atomic properties are calculated, at the mesoscale where morphology, or molecular packing, properties are calculated, and at the device scale, where the device properties are calculated. Chapter 3 describes work that explains why existing methods are inadequate for accurate prediction of device properties from molecular structure. Chapter 4 examines in depth the ways in which small changes to the molecular structure of an OPV material profoundly influences the morphology of the material and properties of the OPV device. In Chapters 5 and 6, properties of two other conjugated systems are studied. Chapter 5 discusses structure-property relationships in ligand-protein binding, specifically how changes to the molecular structure of a green fluorescent protein chromophore affects the extent of fluorescence upon binding to human serum albumin, a protein linked to important human diseases. In Chapter 6, discussion follows the work performed to analyze how swapping the positions of two atoms in a series of small conjugated molecules results in flipping a reactivity switch for a Diels-Alder reaction.