The Study Of The Blue Organic Light Emitting Didoe Performance Based On Connecting Layer

As the new generation display technology in21st century, organic light-emittingdiode （OLED） is known as ‘dream display’, and has tremendous potential application infull color display and white lighting illumination due to its quick response, light weight,ultrathin, large viewing angle and low energy consumption.Most of full color OLEDs and white lighting source consist of red, green, bluecolor emitters. But the researches of blue phosphorescent are still relatively backward.To make a breakthrough in full color and white light, the most important thing isimproving the efficiency of blue phosphorescent OLED. So the effort of the work wasfocused on how to improve the brightness and efficiency of blue OLED and specificcontents are as follows:（1） After choosing host material TCTA, and the best hole transporting layerthickness, the doping concentration radio of blue phosphorescent guest material FIrpicwas optimized. The OLED structure is ITO/TAPC（50nm）/TCTA:FIrpic（30nm, x%）/Bphen （50nm）/Mg:Ag （60nm）. The result demonstrate that when the doping radio is6%,device has better performance, e.g. the max brightness is8981cd/m², max currentefficiency is4.85cd/A, and max power efficiency is1.74lm/W. Compared with deviceswith optimized hole transport layer thickness, the luminance of OLED is increased by100%, and the current efficiency is increased by24%, and power efficiency is increasedby60%.（2） In order to prevent the triplets offset, two emitting layers structure isintroduced.The device of ITO/TAPC（20nm）/TAPC:FIrpic（30nm,6%）/TCTA:FIrpic （30nm,6%）/Bphen（50nm）/Mg:Ag（60nm） was fabricated, and the max brightness reaches15517cd/m², max current efficiency is6.18cd/A, and max power efficiency is2.07lm/W. Compared with single emitting layer OLED, the luminance is increased by72%,and the current efficiency is increased by27%, and power efficiency is increased by19%.（3） To restrict the triplets into emitting layers more effective, green phosphorescentultrathin layer Ir（ppy）₃was insert between emitting layers, Meanwhile, about0.1eV, 0.4eV hole injecting barrier is formed between the HOMO energy levels of Ir（ppy）₃andthose of two hosts, respectively. Therefore, Ir（ppy）₃acts as hole trap, and slows downthe hole transportation, and balances the carriers injection, which could restrict theexciton formation in emitting layers. and the structure was ITO/TAPC（20nm）/TAPC:FIrpic（30nm,6%）/Ir（ppy）₃（1nm）/TCTA:FIrpic（30nm,6%）/Bphen（50nm）/Mg:Ag （60nm）.The device has the max brightness of20323cd/m², max current efficiency of13.18cd/A,and max power efficiency of4.18lm/W. Compared with double emitting layer structuredevices, this device has a31%increase on luminance, a100%increase on the currentefficiency, and a100%increase on power efficiency.（4） Based on two emitting layers structure, orange phosphorescent materialIr（2-phq）₂（acac） is doped in TCTA, then white phosphorescent device could obtained,and doping radio of orange phosphorescent material is optimized. The OLED structureis ITO/TAPC（20nm）/TAPC:FIrpic （30nm,6%）/Ir（ppy）₃（0.5nm）/TCTA:Ir（2-phq）₂（acac）（30nm,x%）/Bphen （50nm）/Mg:Ag（60nm）. When x is5%, the device has the maxbrightness of6995cd/m², max current efficiency of4.76cd/A, and max powerefficiency of1.86lm/W, the color coordinates of the device at8V is （0.34，0.39）.In summary, the research began from the basic OLED structure, then, further studyof introducing double emitting layers and Ir（ppy）₃ultrathin layer was used to limit thetriplets offset with the aim of obtaining better blue phosphorescent devices. This workhas certain reference value in solving the problem of blue phosphorescent OLED.Finally, by adding orange phosphorescent material, white OLED device which colorcoordinates close to white color coordinates （0.33,0.33） were obtained.