Design, Synthesis, and Characterization of Polymer and Small-Molecule Organic Semiconductors based on Tricyclic Heterocycles for Opto-Electronic Devices

Department of Energy EngineeringAs next-generation electronic applications, organic semiconductors based on organic small molecules and polymers with a π -conjugated backbone have shown remarkable results for past decades. In particular, unlike inorganic semiconductors, which have reached the limitation of development, they still have growth potentiality in both industry and academia because of advantages such as low cost, light weight, roll-to-roll (R2R) technology, and so on. Despite tremendous scientific progress, an efficient molecular design and optimization of the fabrication process is needed for further advancement and commercialization of organic electronics. In this work, in order to seek an optimal semiconducting system, organic small molecules/polymers that have various properties were designed and synthesized. The resulting small molecules and polymers were characterized via diverse analysis tools, including NMR, GPC, mass spectroscopy, MADI-TOF, UV-Vis spectrum, TGA, cyclic voltammetry, AFM, XRD, GIWAX. Furthermore, all synthesized organic materials were tested with electronic applications like organic photovoltaics (OPVs) and organic transistors. In the first chapter, the general background of conjugated conducting materials is described to more properly frame the present study. At the same time, essential chemical reactions, mechanisms, and electronic applications are introduced. The second chapter demonstrates synthesis and characterization of benzodipyrrolidone (BDP)-based polymer with electron rich units containing calcogen atoms for OFETs. Thirdly, by tuning the side chain, a powerful and facile control method, polymers based on benzodithiophene (BDT) are designed and synthesized. Subsequently, BDT-based polymer are characterized and applied as active layer of OPVs. Finally, a new class of n-channel semiconducting small molecules based on a BDT core unit, end-capped with the dicyanomethylene and dicyanovinyl groups (DCM-Q-BDT and DCV-B-BDT) was obtained, and their various properties fully analyzed. Furthermore, these molecules were applied as n-type organic transistors and their air stabilities measured.ope