Investigation On Novel Deep Blue Materials In Organic Light-emitting Diodes

After 30 years of development,by virtue of its own advantages,organic light-emitting diode(OLED)is expected to become the next generation of display and lighting technology.To accelerate the practical application of OLED in flat panel displays and solid-state lightings,developing highly efficient blue emission is always essential.In this paper,several deep blue fluorescent materials were designed and synthesized.The UV absorption spectra,PL spectra,low temperature fluorescence and phosphorescence spectra,electrochemical and thermal properties of the composites were characterized.OLEDs based on these deep blue fluorescent materials were investigated.The device is optimized,and the other functions of the material were explored,and a series of innovative results were obtained.1.A new deep blue material DTF was designed and synthesized.Photoluminance(PL)spectral peak position is 433 nm,which is in the deep blue region.The singlet state energy level and triplet state energy level were 2.91 and 2.69 eV respectively.The OLEDs based on DTF were constructed,and the host material and doping concentration of the devices were optimized.The CIE coordinates of the device is(0.157,0.045),the maximum external quantum efficiency is 3.5 % with mild roll-off(3 % at 1000 cd/m~2).2.A new deep blue material TPAF was designed and synthesized.TPAF has good hole transport property,HOMO and LUMO energy levels were-5.4,-2.34 eV.Simple OLEDs based on TPAF with only two layer were constructed and TPAF was used as a hole transport layer and light-emitting layer.The emission of the device is in the deep blue region,the peak wavelength is 414 nm,the CIE color coordinates is(0.160,0.038),and the external quantum efficiency is 2.8%.3.TPAF:B3PYMPM exciplex was found during the investigation of TPAF double-layer fluorescent OLED.In order to further investigate the property of TPAF:B3PYMPM exciplex,doped OLEDs using TPAF:B3PYMPM exciplex as host were constructed.The green phosphorescent material Ir(ppy)2acac,the red phosphorescent material Ir(MDQ)2acac and the red fluorescent material DCJTB were used as dopants respectively,and the turn-on voltage were only 2.28,2.34 and 2.45 V and the maximum external quantum efficiency were 21.4,21.4 and 5.4%,respectively.4.The non-doped OLEDs based on PPi-Pid,PPi-Xid and PPi-Mid were constructed.The emission peak of the devices were 452,440 and 436 nm,the CIE color coordinates were in the deep blue region and the maximum external quantum efficiencies were 4.95,4.51 and 4.60%,respectively.In order to improve the color purity,the doped OLEDs were further constructed.The emission spectra of the devices were blue-shifted to 448,432 and 435 nm,and the CIE coordinates were also improved.The maximum external quantum efficiencies were 5.95,3.90 and 4.28%,respectively.This paper provides more material and device options for the research of deep blue fluorescent OLED and promotes the development of high efficiency deep blue fluorescent OLED.