Theoretical screening of organic conjugated materials

As the urgency to address the effects of climate change increases, so does the need to discover new materials for the generation of renewable energy, to replace the environmentally dam- aging combustion of fossil fuels. Two main areas of research are focused on the design and discovery of photoactive materials for photovoltaics and for photocatalysts for water splitting. Although there are currently high-efficiency photovoltaics commercially available, there is mo- tivation to replace them with materials with non-toxic and earth-abundant compositions. As they generally meet these criteria, organic conjugated materials are very desirable candidates for these applications. Computational chemistry methods can accelerate materials discovery, eliminating the need to synthesize large libraries of molecules in the preliminary screening stages. Both high-accuracy, expensive methods and fast, cheap, lower-accuracy methods have their merits and in conjunction with one another can provide a detailed and informative description of chemical systems. The high-throughput virtual screening methodology used throughout this thesis provides the opportunity to efficiently explore property space and high- light potential candidates for given applications, such as polymeric photocatalysts, organic photovoltaics and dye sensitizers in solar cells. In this thesis this methodology is explored for a small aromatic molecules, diketopyrrolopyrrole-based dyes and both ordered and disordered polymers. Through the high-throughput virtual screening, large datasets of chemical com- pounds were investigated and analysed, highlighting the patterns in the optical and electronic properties influenced by building block sequence, conformerism and composition. The use of high-accuracy, expensive methods is also explored in this thesis, demonstrating the difficulties in pushing such methods to larger chemical structures