Blue organic light-emitting diodes based on fluorene-bridged quinazoline and quinoxaline derivatives

Two blue emitters based on fluorene-bridged quinazoline and quinoxaline derivatives were prepared via the Suzuki reaction. Their photoluminescent properties were investigated. Furthermore, theoretical studies on these materials using the density functional theory calculation were conducted. To explore their electroluminescent properties, multilayered organic light-emitting diodes were fabricated with the following device structure: indium-tin-oxide (180 nm)/4,4'-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (50 nm)/blue emitting materials (1 and 2) (30 nm)/bathophenanthroline (35 nm)/8-hydroxy-quinolinato lithium (2 nm)/Al (100 nm). Two devices showed efficient blue emission with the external quantum efficiencies of 1.58% and 1.30%, respectively, at 20 mA/cm² , and Commission Internationale dÉclairage coordinates of (0.18, 0.24) and (0.19, 0.27) at 6.0 V. These results suggest that the self-aggregation properties of emitters would have considerable effects on their photoluminescent and electroluminescent properties.