Energy-band schemes of highly stable organic electroluminescent devices

Host-guest systems in organic electroluminescent (EL) devices have been studied. Organic EL cells doped with blue to red guest emitters were prepared and their characteristics and the energy bands of the materials were measured. A green EL cell doped with 2,3-quinacridone showed a maximum efficiency of 18.1 lm/W. A yellow EL cell doped with 5,6,11,12-tetraphenylnaphthacene (rubrene) showed a maximum efficiency of 14.4 lm/W and a half-decay time of 25000 h from 130 cd/m/sup 2/. The energy-band schemes of those cells were analyzed and requirements for the scheme and a guest emitter are discussed.