Study On Phosphorescent Materials And Devices Of Pt₂Au₄ Complexes Linked By Aromatic Bis （acetylide） Ligands

Organic light-emitting diodes（OLEDs）are widely used in display and lighting fields due to their advantages such as self-illumination,low energy consumption,fast response,thin and flexible structure,etc.The core of OLED is luminescent material.Currently,commercial OLED green-and red-emitting materials are iridium（III）complexes.There are not only challenging problems such as high price,shortage of iridium resources and short life of blue light materials,but also monopoly of patent rights by foreign countries.Therefore,it is particularly important to develop non-Ir（III）complexes as strongly luminescent materials for ink-jet printing devices.After years of research and exploration,we have designed and synthesized several series of strongly luminescent materials with d⁸-d¹⁰ heteronuclear metal cluster structures by using phosphine ligands as supporting ligands and Pt（II）complexes with aromatic acetylide as precursors,through the strategy of assembly with d¹⁰ metal ions such as Cu（I）,Ag（I）and Au（I）.In this dissertation,a series of phosphorescent materials composed of two Pt Au₂ metal clusters linked by aromatic bis（acetylide）ligands are designed and synthesized by extending the structures of Pt（II）precursors.Solution-process OLEDs based on these phosphorescent Pt（II）-Au（I）complexes achieve high-efficiency and high color purity narrowband electroluminescence.The main work of this dissertation includes three aspects.（1）The structures of the synthons are extended to improve the phosphorescent efficiency of Pt（II）-Au（I）complexes.Bis（acetylide）-bridged dinuclear Pt（II）precursors were designed and synthesized by extending the precursor structures.Two asymmetric Pt Au₂ complexes having HC（?）CC₆H₄C（?）CH（1,4-diethynylbenzene）or HC（?）CCarb C（?）CH（2,7-diethynyl-9-（2,3,5,6-tetrafluorophenyl）-9H-carbazole）and the corresponding bis（acetylide）-linked Pt₂Au₄ complexes are prepared and characterized.Relative to Pt Au₂complexes 1 and 3,bis（acetylide）-linked Pt₂Au₄ complexes 2 and 4 not only display distinct red-shift of the emission,but also provide much higher phosphorescent efficiency.The external quantum efficiencies of the OLEDs based on Pt₂Au₄ complexes 2（11.7%）and 4（19.0%）are obviously higher than those of asymmetric Pt Au₂ complexes 1（8.4%）and 3（11.1%）,respectively.By expanding the structure of the precursors,the luminescent efficiency is significantly improved owing to the enhanced molecular rigidity and the reduced non-radiative deactivation.（2）Modulating narrow-band phosphorescence of Pt₂Au₄ complexes by different positioned bis（acetylide）-naphthalene linkers.To modulate phosphorescent characteristics of Pt₂Au₄ complexes with different positioned bis（acetylide）naphthalene as a bridging ligand,four isomeric Pt₂Au₄ complexes（M1-M4）linked by 1,4-bis（acetylide）naphthalene（M1）,1,5-bis（acetylide）naphthalene（M2）,2,6-bis（acetylide）naphthalene（M3）,and 2,7-bis（acetylide）naphthalene（M4）are elaborately designed and prepared.Depending on the positions of bis（acetylide）groups attached to naphthalene ring,the phosphorescence of Pt₂Au₄ isomers in CH₂Cl₂ solutions follows 1（640 nm）（?）2（582 nm）（?）3（567 nm）（?）4（529 nm）to show progressive blue-shifts.As demonstrated by photophysical and theoretical studies,vibronic-structured narrow-band emissions with a full width at half maxima（FWHM）of 27-36 nm is primarily ascribable to intraligand triplet states localized at bis（acetylide）naphthalene.Solution-processed OLEDs achieve high-efficiency narrow-band electroluminescence with peak external quantum efficiency（EQE）of 11.0%for red-emitting complex 1（FWHM=43 nm）,9.4%for orange-emitting complex 2（FWHM=33nm）,13.7%for yellow-emitting complex 3（FWHM=33 nm）,and 15.2%for green-emitting complex 4（FWHM=24 nm）.The change of the connection position of naphthalene-bis（acetylide）leads to a significant change in the energy gap,thus exerting a significant impact on the luminescence colors of the Pt₂Au₄ complexes.（3）Study on the effect of terminal aromatic acetylene ligands on the luminescence properties of Pt₂Au₄ complexes.Pt₂Au₄ complexes H1-H6 with different terminal alkyne ligands（4-trifluoromethylphenylacetylene,2-ethynyl fluorene or 4-（diphenylamino）phenylacetylene）were designed and synthesized.By adjusting the structure of the terminal alkyne ligand,the luminescence color was regulated.It was found that the Pt₂Au₄complexes always showed the phosphorescent emission characteristics of the organic alkyne ligand with lower energy.Combined with the theoretical calculation results,the luminous color regulation is reasonably explained,and consummate the luminous regulation strategy of Pt₂Au₄ structural complexes.