Organic semiconductors are expected to be applied to photoelectric conversion materials such as transistors, OLEDs, and OPVs by adjusting the HOMO-LUMO gap. We are working on the synthesis of these organic semiconductor materials. For example, acene is a type of aromatic hydrocarbon consisting of linearly fused benzene rings. Notable features of these molecules include an extended flat structure and a narrow gap between the HOMO and His LUMO energy levels. However, these molecules are relatively unstable and have low solubility in common solvents. We have developed a new synthetic route for higher acenes using stable and soluble “precursors.” This precursor quantitatively generates an acene structure upon heating or irradiation with light. By applying this method, it is possible to develop organic semiconductor materials.

Most of the components of sunlight are visible light and near-infrared/infrared light, and there is a need for methods to efficiently utilize these components. Since the energy gap of organic semiconductors can be easily adjusted, it is possible to develop materials tailored to the photochemical reaction potential in the visible to near-infrared region. We are researching the interface chemistry of organic-inorganic semiconductors, such stabilization, and formation of charge separation states between interfaces created by developing targeted organic semiconductors and combining them with inorganic semiconductors. Using organic/inorganic semiconductor composite photocatalysts, we are developing water splitting, hydrogen peroxide synthesis, carbon dioxide reduction, or photoelectrochemical reactions.