Optionally substituted bipyridine compounds, optionally substituted phenylbipyridine compounds, or optionally substituted bis-phenylbipyridine compounds may be useful in light-emitting devices. Some examples include, but are not limited to, optionally substituted 4-(5-(6-(4-(diphenylamino)phenyl)pyridin-3-yl)pyridin-2-yl)-N,N-diphenylbenzenamine, optionally substituted 9-(4-(5-(6-(4-(9H-carbazol-9-yl)phenyl)pyridin-3-yl)pyridin-2-yl)phenyl)-9H-carbazole, optionally substituted 4-(5-(6-(benzo[d]thiazol-2-yl)pyridin-3-yl)pyridin-2-yl)-N,N-diphenylbenzenamine, optionally substituted 4-(5-(6-(benzo[d]oxazol-2-yl)pyridin-3-yl)pyridin-2-yl)-N,N-diphenylbenzenamine, optionally substituted N,N-diphenyl-4-(5-(6-(1-phenyl-1H-benzo[d]imidazol-2-yl)pyridin-3-yl)pyridin-2-yl)benzenamine, optionally substituted 4-(5-(6-(4-(9H-carbazol-9-yl)phenyl)pyridin-3-yl)pyridin-2-yl)-N,N-diphenylbenzenamine, optionally substituted 2-(5-(6-(benzo[d]thiazol-2-yl)pyridin-3-yl)pyridin-2-yl)benzo[d]thiazole, optionally substituted 2-(5-(6-(benzo[d]thiazol-2-yl)pyridin-3-yl)pyridin-2-yl)benzo[d]oxazole, optionally substituted 9-(4-(5-(6-(benzo[d]thiazol-2-yl)pyridin-3-yl)pyridin-2-yl)phenyl)-9H-carbazole, optionally substituted 9-(4-(5-(6-(benzo[d]oxazol-2-yl)pyridin-3-yl)pyridin-2-yl)phenyl)-9H-carbazole, optionally substituted 9-(4-(6′-(1-phenyl-1H-benzo[d]imidazol-2-yl)-3,3′-bipyridin-6-yl)phenyl)-9H-carbazole, and 6,6′-bis(9-phenyl-9H-carbazol-3-yl)-3,3′-bipyridine.