Light-emitting device, electronic device, and lighting device
摘要
說明書
The third aromatic ring is a substituted or unsubstituted monocyclic condensed ring or a substituted or unsubstituted bicyclic or tricyclic condensed ring. Since the refractive index tends to increase with an increase in the number of the condensed rings, using an aromatic group with a small number of condensed rings enables the refractive index to be maintained low. Similarly, an increase in the number of the condensed rings leads to absorption and emission of light in the visible region that are to be observed, and thus using an aromatic group with a small number of condensed rings can reduce the influence of the absorption and emission of light. Note that the third aromatic ring preferably has 6 to 13 carbon atoms to maintain the low refractive index. Specific examples of the aromatic group that can be used as the third aromatic group include a benzene ring, a naphthalene ring, a fluorene ring, and an acenaphthylene ring. In particular, the third aromatic ring preferably includes a fluorene ring and further preferably is a fluorene ring, in which case the hole-transport property can be favorable.
