Using Fluorescent Materials With High Exciton Utilization To Fabricate Deep-Blue OLEDs And White OLEDs

In recent years,organic light-emitting diodes(OLEDs)have attracted much attention in the display and lighting fields due to their advantages of lightness,thinness,self-luminescence,wide color gamut,and low power consumption.With the commercialization of OLEDs,higher requirements have been placed on the efficiency,light color,and stability of luminescent materials.However,blue luminescent materials have always been the bottleneck in the development of OLEDs.To solve this problem,fluorescent materials with high exciton utilization have become the focus of the development of deep-blue OLEDs.In this thesis,we mainly study the fabrication of deep-blue fluorescent OLEDs with luminescence mechanism of TTA and HLCT,and then,we explore the preparation process of white organic light-emitting diodes(WOLEDs).Two novel deep-blue luminescent materials(CZ-TAn-DMAC and TPA-TAn-DMAC),which are composed of tert-butylanthracene,dimethylacridine and carbazole or triphenylamine groups,are successfully synthesized.Based on these two compounds,we design the device structure of monochromatic OLED.Notably,non-doped OLED based on TPA-TAn-DMAC with simple device structure achieves bright deep-blue emission(CIE_x,y=0.14,0.18)and the maximum external quantum efficiency of 4.9%.The doped OLED based on Cz-TAn-DMAC(doped into the host CBP at concentration of 10 wt%)shows a bluer emission at 431 nm(CIE_x,y=0.15,0.08),and compared with non-doped OLED,the external quantum efficiency(4.8%)is improved a lot.In addition,fluorescent-phosphorescent hybrid WOLEDs based on TPA-TAn-DMAC are fabricated.By optimizing device configurations,a series of warm WOLEDs with high luminescence stability,high efficiency and stable color emission are prepared.These WOLEDs can also maintain high luminous efficiency and spectral stability even at luminance over 30,000 cd m^-2,and have a high application prospect in the future lighting field.We study the photophysical properties of the compounds(DSIPPI and CSIPPI)modified with trimethylsilane,and explore the multifunctional uses of these two molecules in monochromatic OLEDs,phosphorescent OLEDs and WOLEDs.The CSIPPI-based non-doped OLED achieves a deep blue emission of 404 nm(CIEx,y=0.16,0.06)and a maximum external quantum efficiency of 7.13%.The DSIPPI-based doped device achieves a near-ultraviolet emission of 393 nm(CIE_x,y=0.15,0.05)and a maximum external quantum efficiency of 7.35%.Furthermore,the orange phosphorescent OLED based on the bipolar host DSIPPI realizes a maximum external quantum efficiency of 23%and a maximum power efficiency of 74.1 lm W^-1.In addition,the three-color WOLED based on CSIPPI exhibits white light emission with a high color rendering index(CRI)of 90 and high spectral stability(CIE_x,y=0.30,0.37).We study the photophysical properties of new deep-blue luminescent materials(2DPA-PhBI,2Cz-PhBI,2DPA-BI,2Cz-BI)with benzimidazole as the core.The OLED device based on 2CZ-PHBI with the doping concentration of 10 wt%achieves a maximum external quantum efficiency of 8.1%,and deep-blue emission with high color purity(CIE_x,y=0.16,0.04).