Host-guest systems in organic electroluminescent (EL) devices have bee
n studied. Organic EL cells doped with blue to red guest emitters were
prepared and their characteristics and the energy bands of the materi
als were measured. A green EL cell doped with 2,3-quinacridone showed
a maximum efficiency of 18.1 Im/W. A yellow EL cell doped with 5,6,11,
12-tetraphenylnaphthacene (rubrene) showed a maximum efficiency of 14.
4 Im/W and a half-decay time of 25000 h from 130 cd/m(2), The energy-b
and schemes of those cells were analyzed and requirements for the sche
me and a guest emitter are discussed.