High-efficiency non-doped deep-blue fluorescent organic light-emitting diodes based on carbazole/phenanthroimidazole derivatives

It is a persistent challenge to develop efficient, low roll-off, pure blue light emitting materials. Here, employing rigid carbazole (Cz) and phenyl-phenanthroimidazole (PPI) moieties to reduce the energy loss caused by non-radiative transitions, two deep-blue fluorescent emitting materials, 2-(4-(9H-carbazol-9-yl)phenyl)-1-(3,5-difluorophenyl)-1H-phenanthro[9,10-d]imidazole (2FPPICz) and 2-(4′-(9H-carbazol-9-yl)-[1,1′-biphenyl]-4-yl)-1-(3,5-difluorophenyl)-1H-phenanthro[9,10-d]imidazole (2FPPIPCz), are synthesized and fully characterized. The non-doped organic light-emitting diodes (OLEDs) with 2FPPICz and 2FPPIPCz as emitters represent deep-blue emission with Commission International de L’Eclairage (CIE) coordinates of (0.160, 0.045) and (0.150, 0.075) and an excellent maximum external quantum efficiency (EQE) of 4.3% and 5.6%, respectively. Furthermore, the OLED with 2FPPIPCz exhibits low efficiency roll-off at high luminance.