High-Efficiency Near Ultraviolet and Blue Organic Light-Emitting Diodes Using Star-Shaped Material as Emissive and Hosting Molecules

We have investigated the fluorescent and hosting properties of a novel star-shaped material (SSM) containing carbazole/arylamine backbone. Using SSM as an emitter, we have fabricated a near ultraviolet-emitting electroluminescent device with a peak emission at λ_peak = 408 nm and achieved a maximum external quantum efficiency of 2.56%. We have also demonstrated that SSM can be employed as an effective hosting material of high-efficiency blue organic light-emitting diode, in which the maximum current and power efficiencies reached 10.37 cd/A and 8.69 lm/W, respectively. We have also found that the side-band emission of blue p-bis( p-N, N-diphenyl-amino-styryl) benzene electroluminophore could be completely suppressed with the aid of SSM being hosting matrix. Hence, SSM-based blue device has a higher color-purity than 4,4´-bis(9-carbazolyl)biphenyl-based one, of which the y-value of color coordinates and the full-width half-maximum decreased from 0.45 to 0.36, and from 62 to 37 nm, respectively.