Synthesis, photophysical and electroluminescent properties of phenanthroimidazole derivatives with terminal carbazole or pyrene

New phenanthroimidazole derivatives PSC, PDC, PCC and PPP bearing terminal carbazole or pyrene unit have been synthesized. They exhibited excellent solubility in common organic solvents. It was found that the obtained phenanthroimidazole derivatives could emit strong fluorescence in cyclohexane, and the fluorescence quantum yields of the phenanthroimidazole derivatives were in the range of 0.49–0.83 using quinine sulfate (0.1 N in H2SO4) as a standard. We fabricated the organic light-emitting diode with the configuration of ITO/NPB (45 nm)/phenanthroimidazole derivatives (15 nm)/TPBI (40 nm)/LiF/Al, and a saturated blue emission with CIEx,y of (0.16, 0.17) was achieved from the device based on PSC. In addition, the devices based on other phenanthroimidazole derivatives could emit bluish green or green light. The turn-on voltage, current efficiency and maximum luminance of the devices based on PSC, PDC, PCC and PPP were 3.4 V, 3.4 V, 3.8 V, 3.4 V and 0.92 cd/A, 1.83 cd/A, 1.28 cd/A, 0.32 cd/A, as well as 1190 cd/m2, 1930 cd/m2, 1270 cd/m2, 1149 cd/m2, respectively, meaning the phenanthroimidazole derivatives might become candidates as emitting materials employed in OLEDs.