Investigation Of Non-energy Transfer WOLEDs Utilizing ESIPT Materials With TADF Characteristics

Organic light-emitting devices?OLEDs?have been widely used in advanced display field,and they are likely to become the core products of display industry in the future.White light organic light-emitting devices?WOLEDs?have attracted much attention because of their great potential applications in solid-state lighting and full-color display.In order to achieve the white light,researchers usually adopt two methods:two-complementary-colors or three-primary-colors.The white emission is based on the incomplete energy transfer between the different-colared luminescent components.However,due to the difficulty of precisely controlling the degree of energy transfer,the obtained white light is often not ideal.Although the multi-luminescent-layer structure can reduce the energy transfer among the luminescent components,the ideal white light also cannot be obtained due to the complex structure and inconsistent decay life of the materials in each luminescent layer.Moreover,the efficiency of white-light organic light-emitting devices fabricated by ordinary fluorescent materials is not ideal.In order to obtain organic light-emitting devices with simple structure,higher device performance and ideal white light emission,a yellow light-emitting material SPDDBD-1 and a green light-emitting material SPDDBD-2 based on excitation intramolecular proton transfer and delayed fluorescence have been designed and synthesized,respectively.In the solution state,the lifetime of the product increases obviously after the sample was degassed by nitrogen.After theoretical calculation,the minimum energy gap(?E_st)of the singlet and triplet states is only 0.02 eV.Both above phenomenon confirm the characteristics of delayed fluorescence.The structure of ITO/NPB?40 nm?/CBP:SPDDBD-1?20 nm?/TPBi/?60 nm?/LiF/Al is designed and the lifetime measurments of CBP:SPDDBD-1 hybrid film with different dopping ratios show that there is no energy transfer between host and guest components.By adjusting the doping ratio,when the doping ratio of SPDDBD-1 is 15%,the luminescent color is close to the ideal white light,with the CIE coordinates of?0.333,0.330?.The maximum current efficiency of the device is 3.2 cd/A and the maximum external quantum efficiency is 1.67%.To further improve the device performance,the blue-emitting thermally activated delayed fluorescent?TADF?material DMAC-DPS is introduced into the luminescent layer.When the ratio of blue DMAC-DPS to yellow SPDDBD-1 is 4:1,the emission color of the device is close to the ideal white light,with the CIE coordinates of?0.328,0.336?.The maximum current efficiency is14.83 cd/A and the maximum external quantum efficiency is 6.08%.