| White organic light-emitting diodes have drawn tremendous attention and areexpected to dominate the next-generation flat-panel display and solid-state lightingdue to their merits of ultra-thin, light weight, and environmental friendliness. Whiteorganic light-emitting diodes should possess the characteristics of high efficiency,high color stability, low roll-off, high Color Rendering Index for theircommercialization. In order to fulfill the demands above, the selection of thematerials used in white organic light-emitting diodes and the optimization of devicestructures would be necessary. Our works mainly focus on enhancing the colorstability and improving Color Rendering Index of white organic light-emittingdiodes, reducing the roll-off of the device efficiency. We have done the followingwork which aimed at improving the performance of white organic light-emittingdiodes:Firstly, we demonstrated hybrid white organic light-emitting diodes byintroducing the combination of fluorescence material and phosphorescence material.We took the PO-01doped CBP as the yellow emission layer and the DSA-ph dopedMADN as the blue emission layer，and then the Ir(ppz)3was introduced as theinterlayer between the yellow emission layer and the blue emission layer to balancethe carriers among the emission layers. The structure of the optimized device isITO/m-MTDATA (45nm)/Ir(ppz)3(10nm)/CBP: PO-01(5nm,6wt.%)/Ir(ppz)3(1nm)//MADN: DSA-ph (25nm,5wt.%)/BPhen (50nm)/LiF (1nm)/Al (100nm),high color stability device with negligible efficiency roll-off is finally obtained afteroptimization. The corresponding device shows high current efficiency of21.0cd/Aat2,300cd/m2and20.1cd/A at9,300cd/m2with CIE coordinates change marginallyfrom (0.41,0.46) to (0.40,0.46) over103–104cd/m2.Nextly, we demonstrated a series of color stable Multi-Emission Layer whiteorganic light-emitting diodes based on all-phosphor emitters using Ir(ppz)3as interlayer, The results prove that less than2nm thickness of Ir(ppz)3interlayer notonly can control exciton distribution in the Emission layer, but also can improve thespectra stability. In particular, an efficient four-color device shows an excellentColor Rendering Index above90with idea Correlated Color Temperature valuesover the illumination-relevant luminance of100cd/m2and1,000cd/m2, making itwell suited for lighting applications. High color quality device with excellent colorand efficiency stability is eventually implemented by further manipulating carriertransport with appropriate host material to balance carrier injection. |
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