超低效率滚降顶发射白光有机电致发光器件

Ultra-low Efficiency Roll-off Top-emitting White Organic Light-emitting Diodes

利用Ag/tris-(8-hydroxyquinoline)aluminum(Alq_(3))/Ag/Alq_(3)/Ag这一金属/有机半导体多层结构作为阳极,实现了超低效率滚降的顶发射白光器件。在该器件中,我们在蓝光和橙光发光单元之间引入一个薄的4,4′-bis(9-carbazolyl)-2,2′-biphenyl(CBP)层,从而减少橙光发光层与蓝光发光层的Dexter能量传递,用以改善白光器件发光光谱及效率。通过优化微腔设计,实现了对橙光磷光材料发射的调控。最终,我们获得了在60000 cd/m^(2)亮度下效率滚降仅为17%的顶发射白光器件。在效率方面,虽然顶发射白光器件与底发射白光器件不相上下,但由于微腔效应的存在,顶发射白光器件的效率滚降却远低于底发射白光器件的效率滚降。

White top-emitting organic light-emitting devices(TEOLEDs)with very low efficiency roll-off are obtained by utilizing Ag/Alq_(3)/Ag/Alq_(3)/Ag as an anode.A neat bipolar transport 4,4′-bis(9-carbazolyl)-2,2′-biphenyl(CBP)layer is introduced between the blue fluorescent and the orange phosphorescent emission layers in order to reduce the Dexter energy transfer between the two emissive units,which can improve the emission spectrum and device efficiency.The yellow emission from bis(2-(2-fluorphenyl)-1,3-benzothiozolato-N,C2′)iridium(acetylacetonate)is manipulated by optimizing the microcavity effect of the TEOLED.As a result,we demonstrate that a very low roll-off of 17%for the current efficiency can be obtained at a super high luminance of 60000 cd/m^(2).The efficiencies of the white TEOLEDs are comparable to those of the corresponding conventional bottom-emitting OLED.In comparison,the efficiency roll-off of the TEOLEDs is much lower than that of the corresponding conventional bottom-emitting device due to the microcavity effects.