Design,Synthesis And Electroluminescent Performance Based On Spiro-acridine-fluorene Blue Emitting Materials

In this paper,five blue light-emitting materials containing spiro[acridine-9,9’-fluorene],phenanthroimidazole or cabazole,two blue-green emitting materials based on hydroxyl-substituted pyrene-imidazole,as well as two tunable emissionβ-diketone derivatives,were designed and synthesized.These compounds were characterized by infrared spectroscopy（IR）,nuclear magnetic resonance（NMR）spectroscopy,mass spectrometry（MS）or elemental analysis.Their molecular structure-property relationships were evaluated by means of thermal,electrochemical,photophysical,frontier orbital distribution and carrier transporting studies.Subsequently,these disciplines will enlighten us how to design highly efficient blue light-emitting materials.And the organic light-emitting diodes（OLEDs）based on these emitters were investigated.Three deep-blue emitters,namely SAF-Cz B,SAF-2Cz B and F-2Cz B,were designed and synthesized.The carbazole serve as the blue-light chromophore.The spiro[acridine-9,9’-fluorene]（SAF）or 9,9’-dimethylfluorene apply as the core.Introduction of SAF into fluorene-based materials could simultaneously reduce intermolecular aggregation,improve hole injection and transport ability,as well as prevent the fluorenone defect.The decomposition temperature（T_d）of the three compounds are 429,534 and 488℃,respectively.Their melting point（T_m）are 302,390 and 243℃,respectively.The single-hole device demonstrated that the compound SAF-2Cz B possesses the best hole-transporting ability.Non-doped blue OLEDs based on SAF-Cz B,SAF-2Cz B,F-2Cz B as emitting layer shows maximum current efficiency of 3.03,4.07 and 3.14 cd A^-1,power efficiency of 1.08,1.83 and 1.23 lm W^-1,Commission International de L’Eclairage（CIE）coordinate of（0.20,0.16）,（0.16,0.11）and（0.16,0.11）,respectively.The biplolar blue light-emitting material SAF-BPI,incorporating phenanthroimidazole（BPI）as acceptor part and spiro-acridine-fluorene（SAF）as donor part,was designed and synthesized.The phenanthroimidazole is used as electron-transporting unit and spiro-annulated triphenylamine is utilized as hole-transporting unit.Owing to the rigid SAF skeleton,this compound exhibits high decomposition temperature（T_d）of 498℃and glass transition temperature（T_g）of198℃.The non-doped OLEDs based on the SAF-BPI as the emitting layer shows maximum luminance of 2122 cd m^-2,maximum current efficiency（CE）of 3.97 cd A^-1,and maximum power efficiency of 2.08 lm W^-1.The chromaticity coordinate is stable at（0.15,0.10）at the voltage of 7-11 V.The device shows a slow efficiency roll-off with CE of 3.35,2.85 cd A^-1at 100,1000 cd m^-2,respectively.The linear-arranged blue light-emitting material 27BPI-SAF,consisting of phenanthroimidazole and spiro-acridine-fluorene,was designed and synthesized.The decomposition temperature（T_d）is 571℃.In film,the maximum emission peak locates at 445 nm.The HOMO are primarily distributed on spiro-annulated triphenylamine and LUMO are mainly localized on the fluorene and bridged-linkage phenyl-ring.The non-doped blue device shows maximum luminance of 3564 cd m^-2,current efficiency（CE）of 1.48 cd A^-1,and power efficiency（PE）of 0.48 lm W^-1.Obviously,the efficiency roll-off of the device is relatively small with CE of 1.42,1.25,and 1.02 cd A^-1at 1000,2000 and 3000 cd m^-2,respectively.The blue-green emitters based-on excited state intramolecular proton transfer,namely Py I-P and Py I-TPA,was designed and synthesized.The tunable emissionβ-diketone derivatives with D-π-A-π-D structure,namely Dk-TPA and Dke-TPA,was synthesized.