Study On Solution Processable Fluorescent/Phosphorescent Hybrid White OLED

White light organic light-emitting diodes?WOLEDs?have not only been well developed in the solid-state light source market,but also attracted more and more attention in the display field.The luminescent materials used in the fluorescent/phosphorescent hybrid WOLEDs have a great influence on the device performance.So among them,dendritic fluorescent materials are characteristic of the encapsulation effect on the fluorescence core,owing to the massive surrounding branches.Benefiting from this feature,the energy back-transfer from the high-lying triplet of phosphors to the low-lying triplet of fluorescent emitters can be substantially avoided in the fluorescence/phosphorescence mixing system.Based on above,a series of dendritic blue fluorescent materials with perylene as the emitting core is synthesized,and an orange phosphor composed of ruthenium and furan[3,2-c]pyridine is also obtained as needed.With both in hand,fluorescence/phosphorescence hybrid electroluminescent devices are prepared and evaluated systematically.Starting from the perylene core,oligomeric carbazoles are attached sequently according to a succession of coupling reactions to give the first and the third generation of dendritic compound?Pe-D1 and Pe-D3,respectively?.It is found that both of them have good chemical and thermal stability and excellent solubility in common organic solvents,which fulfill the requests of solution-process.In the meantime,those dendrimers have suitable HOMO/LUMO energy levels,leading to the smooth injection of charge carries in OLED devices.After that,a new furan[3,2-c]pyridine based ruthenium complex?3,5-diMeOpfu py?₂Ir?acac?is designed and synthesized.The introduction of methoxy group at the 3_rd and5_th position of the phenyl ring prevents the formation of unwanted isomers without altering the luminescent properties.At the same time,the methoxy group increases the solubility of the complex in organic solvents such as chlorobenzene,which is advantageous for the preparation of devices using the low-cost wet process.The solution-processed electroluminescent device based on?3,5-diMeOpfupy?₂Ir?acac?achieves a maximum external quantum efficiency of 8.9%,together with the maximum current efficiency of 17.1cd/A and the maximum power efficiency of 18.4 lm/W.Finally,nondoped devices are prepared using the purchased fluorescent material TBPe and the synthesized fluorescent materials Pe-D1 and Pe-D3 as the emitting layer,and among which the Pe-D3 shows the best performance.To further improve the device performance,a set of doped devices are also prepared,choosing mCP as the host material at the doping ratio of 1%,3%and 5%,respectively.And the device with the ratio of 1%obtained the best performance,the maximum current efficiency reached 7.69 cd/A.In the end,another set of hybrid devices are constructed,blending 1%Pe-D3 in mCP with?3,5-diMeOpfupy?2Ir?acac?at the doping ratio of 0.2%,0.4%and 0.6%,respectively.The device with the ratio of 0.4%gives a bright white emission,whose CIE is?0.34,0.36?,along with the maximum brightness of 3413 cd/m²,the maximum current efficiency of 6.57 cd/A and the maximum power efficiency of 3.13 lm/W.To conclude,this work provides more optimization schemes for the research of fluorescent/phosphorescent hybrid WOLEDs,and promotes the development of high-performance WOLEDs.