Highly Efficient Phosphorescent Green Organic Light-Emitting Diodes with High Energy Gap Host Materials

We investigated the electroluminescent characteristics of three devices which were fabricated with a green phosphorescent emitter bis[2-(o-terphen-3-yl)pyridinato-C,N]iridium(III) (acetylacetonate) [(tppy)2Ir(acac)] doped in triphenylsilane-based host materials, such as 4,4′-bis(triphenylsilyl)biphenyl (BSB), 9,9′-spirobifluorene-2-yltriphenylsilane (SFS) and (4-(10-(naphthalene-2-yl)anthracen-9-yl)phenyl)triphenylsilane (ANPTPS), which have the different the triplet energy levels (E T) of 2.61 eV, 2.64 eV and <1.91 eV, respectively. Among those, two devices using BSB and SFS hosts with the suitable E T energy levels to green phosphorescent dopant exhibited the highly efficient green electrophosphorescence with the maximum luminous efficiencies of 51.3 cd/A and 46.6 cd/A, respectively, and the maximum quantum efficiencies of 13.9% and 12.4%, respectively.