低效率滚降、发光颜色稳定的磷光白色有机电致发光器件

本文采用多发光层结构,制备了高亮度下具有高发光效率,同时在较宽亮度范围内发光颜色稳定的白色磷光有机电致发光器件(WOLED).在对双发光层结构磷光OLEDs的发光机制和载流子传输过程进行系统研究的基础上,将两种磷光OLEDs的发光层结构相结合,获得的多发光层结构磷光WOLED最大电流效率和外量子效率分别为34.6 cd/A和13.5%;当亮度为1000 cd/m^2时,其电流效率和外量子效率分别为33.9 cd/A和13.3%,外量子效率滚降仅为1.5%;亮度从1000 cd/m^2增至10000 cd/m^2的过程中,其CIE色度坐标从(0.342,0.403)变化至(0.326,0.392),变化量ΔCIE为(0.016,0.011).

Highly efficient all-phosphorescent white organic lightemitting diodes with low efficiency roll-off and stable-color by managing triplet excitons in emissive layer

White organic light-emitting diodes(WOLEDs)have drawn considerable attention for next-generation lighting and display applications owing to their remarkable advantages.Phosphorescent OLED technology is crucial to realize high-efficiency white OLEDs because phosphorescent emitters enable to achieve almost 100%internal quantum efficiency(IQE)by harvesting all the excitons of 75%of triplets and 25%of singlets.However,an efficiency roll-off at high-brightness and a shift in color under various operation biases remains challenges.With the goal towards commercial applications,it requires WOLEDs should simultaneously realize high efficiency at high-brightness region over 1000 cd/m2 and good color stability over a wide electroluminescent range.In this paper,we first investigated the energy transfer process between the blue-emitting Bis 3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III)(Firpic)and the orange emitting Iridium(III)bis (4-(4-tert-butylphenyl)thieno3,2-c]pyridinato-N,C2') acetylacetonate(PO-01-TB),in addition to the behavior of the carrier trapping in the phosphorescent OLEDs with double emissive layers.Then we successfully fabricated phosphorescent WOLED with multiple emissive layers.The resulting phosphorescent WOLED achieves the maximum forward-viewing current efficiency(CE)of 34.6 cd/A and external quantum efficiency(EQE)of 13.5%,and the CE and the EQE remain 33.9 cd/A and 13.3%at 1000 cd/m2,respectively,indicating that the WOLED exhibits low efficiency roll-off.Furthermore,the WOLED shows very stable white emission with small Commission Internationale de L’Eclairage(CIE)coordinate varying range of(0.016,0.011)from 1000 to 10000 cd/m^2.The results provide a promising avenue to simultaneously achieve high efficiency,lower the efficiency roll-off at high brightness and color-stability for phosphorescent WOLEDs by carefully designing the device architecture to redistribute the charge carriers and excitons in the recombination zone.