High-efficiency electroluminescence from new blue-emitting oligoquinolines bearing pyrenyl or triphenyl endgroups

New n-type conjugated oligomers bearing pyrenyl or triphenyl endgroups, 6,6'-bis(2-(1-pyrenyl)-4-phenylquinoline) (BPYPQ) and 6,6'-bis(2-(1-triphenyl)-4-phenylquinoline) (B3PPQ), were synthesized and found to be efficient blue emitters for organic light-emitting diodes (OLEDs). The oligoquinolines were thermally robust with high decomposition temperatures of 521-538 degrees C and high melt transitions (379-447 degrees C). The oligoquinolines emitted blue fluorescence in solution with high quantum yields (86-91%) and lifetimes of 1.31 ns for BPYPQ and 0.82 ns for B3PPQ. B3PPQ showed ambipolar redox properties, with a HOMO level of 5.78 eV and a LUMO level of 2.58 eV. BPYPQ had a reversible electrochemical reduction, with a HOMO level of 5.86 eV and a LUMO of 2.66 eV. Bright blue electroluminescence (3900 cd/m(2)) with high efficiency (2.6 cd/A and 3.2% external quantum efficiency) were achieved from B3PPQ as the emitter in OLEDs. Far superior device performance was achieved with BPYPQ as the emissive material, with a maximum luminance of 13885 cd/m(2), an external quantum efficiency of 3.5% (at 5375 cd/m(2)), and a luminous efficiency of 7.2 cd/A. The new triphenyl- and pyrenyl-bearing oligoquinolines are markedly thermally robust and are useful highly emissive and electron transport materials for OLEDs.