Quinacridone dyes were originally used as red pigments having clear color and durability. They are useful for painting of automobiles, printing ink and coloring of plastics. In the research field of organic electronics, quinacridone dyes are applied to solar cells and organic light-emitting diodes (OLED). Quinacridones easily show intermolecular stacks in face-to-face mode and form strong intermolecular hydrogen bondings (NH•••O). Thus, these facts indicate that quenching of emission occurs under a concentrated condition. On the other hand, quinacridone dyes are strongly luminescent in solution, and are useful for luminescent dopant materials even if they are used in the solid state. In fact, they are green luminescent dopants for an OLED device. In order to decrease intermolecular hydrogen bonding, we can introduce a group on the nitrogen to avoid intermolecular quenching. Introduction of alkyl groups enhances solubility, because quinacridones usually are poorly soluble.
