| 초록 |
Herein we report a new host material for blue electrophosphorescence devices, 1,2-Di(9H-carbazol-9-yl)cyclobutane (DCz). DCZ has the 1,2-trans configuration between adjacent carbazole units, which effectively suppresses the formation of carbazole-excimers. In addition, this molecular structure enables much greater concentration of carbazole moiety, giving higher charge transporting ability. From the photophysical study, we found that excimer formation of carbazole units was efficiently suppressed to give the exclusive monomer emission. It was also found that the T1 level of DCz (2.88eV) was higher than the blue guest phosphor, Firpic, to bring about the exothermic energy transfer. A preliminary electrophosphorescent device (ITO/NPB/Host:FIrpic/BAlq/LiF/Al) showed an improved device efficiency (max. ηext=9.8%, max. ηpow=15.0 lm/W, max. ηL=21.5 cd/A) compared to those using mCP as a comparative host (max. ηext=9.3%, max. ηpow=13.2 lm/W, max. ηL=20.4 cd/A). |
