Efficient organic blue fluorescent light-emitting devices with improved carriers' balance on emitter molecules by constructing supplementary light-emitting layer

• Pure blue electroluminescent devices were designed and fabricated.
• Matched energy levels help to facilitate the trapping of carriers.
• The presence of supplementary light-emitting layer broadens the recombination zone.
• Improved carriers' trapping suppresses the emission of host material.

In this work, we demonstrated an efficient device design strategy in improving the electroluminescent performances of blue fluorescent emitter 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl (BCzVBi) by constructing predominant and supplementary light-emitting layers. 4,4′,4″-tris(carbazole-9-yl)triphenylamine (TcTa) and 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) were selected as host materials. Experimental results revealed BCzVBi doped TcTa film functions as predominant light-emitting layer, while BCzVBi doped 26DCzPPy film functions as supplementary light-emitting layer, which helps to broaden the recombination zone, improve the trapping of carriers and balance the distribution of holes and electrons on emitter molecules. Finally, the 15 wt% doped device with the Commission Internationale de 1′Eclairage coordinates of (0.143, 0.189) obtained the maximum current efficiency, power efficiency, external quantum efficiency and brightness up to 11.99 cd/A, 10.91 lm/W, 8.0% and 36,060 cd/m2, respectively. Even at the high brightness of 1000 cd/m2, current efficiency as high as 9.76 cd/A can be retained by the same device.

Highly efficient blue electroluminescent (EL) devices were designed and realized by doping fluorescent emitter 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl (BCzVBi) into 4,4′,4″-tris(carbazole-9-yl)triphenylamine (TcTa) and 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) films as predominant and supplementary light-emitting layers, respectively.Figure optionsDownload as PowerPoint slide