| White organic light emitting diodes is regarded as the new generation of lighting source due to the advantages of uniform luminescence,spontaneous light and plane light source.The realization of white light depends on the emission of three primary colors or complementary colors,which also need the highly efficient monochromatic emission.The exciplex formed from intermolecular charge transfer between donor and acceptor could achieve 100%internal quantum efficiency in theory due to the efficient triplet excitons reverse intersystem crossing（RISC）process with intrinsic smallΔEST.Moreover,the natural wide full width at half maximum（FWHM）of exciplex emission is beneficial to improve the color quality of WOLED.However,there are still some problems in all exciplex WOLED,such as complicated device structure and low efficiency.Here,the thesis studies monochromatic and white OLED based on all exciplex emission.The WOLED with high efficiency/luminance/color quality are expected to achieve with complementary color strategy through selecting high-efficiency monochromatic exciplex,controlling exciton recombination zone,balancing carrier injection/transport and designing rational device structure.The main research contents are as follows:1.A series of monochromatic exciplex OLED were designed according to the HOMO/LUMO energy level by utilizing different donor materilas and one acceptor matrial of PO-T2T,respectively,finally a full spectra coverage in visible light range was achieved with exciplex emission.The influence of energy level barrier on radiative transition and emission color is analyzed by combining the molecular structure of donor and the band gap of donor/acceptor.The maximum external quantum efficiency（EQE）of blue exciplex of26DCz PPy:PO-T2T and yellow exciplex of DMAC-MPM:PO-T2T are 6.47%and 10.47%,respectively,which is contribute to construct efficient WOLED in the following chapters with complementaty color strategy.2.WOLED with yellow（orange）exciplex/spacer/blue exciplex as the emitting layer structure was designed and fabricated.The effects of spacer materials with different properties on luminescence properties and exciton recombination zone were studied systematically.The spacer of donor material of DMAC-MPM and 26DCz PPy,acceptor material of PO-T2T and inert material of DPEPO were selected,respectively,to modulate the exciton recombination zone by optimizing the spacer thickness.Finally,WOLED with 4 nm spacer of 26DCz PPy achieved the low turn-on voltage of 3.3 V,high luminance of 8153 cd/m2,high EQE of 7.9%and CIE at（0.28,0.44）.On this basis,the device structure and energy level arrangement were further optimized,and the yellow exciplex of DMAC-MPM:PO-T2T was replaced with orange exciplex of TAPC:PO-T2T.When the spacer of 26DCz PPy in 4 nm,the CIE of the device are stable at（0.32,0.43）,and the maximum luminance,current efficiency（CE）,power efficiency（PE）and EQE were 5788 cd/m2,19.3 cd/A,16.9 lm/W and 7.6%,respectively.3.The single-emitting layer（S-EML）structure WOLED based all exciplex emission through ternary donor/acceptor system were designed in this section.The complementary color strategies of m CP:PO-T2T:m-MTDATA（1:1:x wt%）,26DCz PPy:PO-T2T:m-MTDATA（1:1:x wt%）and TAPC:TPBi:PO-T2T（1:1:x wt%）were designed for the S-EML structure.The white emission could be constructed by the simultaneous emission of blue and orange exciplex through adjusting the concentration of dopant and changing the ratio of double exciplexes.Finally,the first all exciplex WOLED based on S-EML structure were achieved successfully with the optimized maximum luminance of～3500 cd/m2 and maximum EQE of～3%,respectively.Besides,the CRI could reach～80 with the two complementary colors exciplex emission. |
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