Synthesis And Electroluminescent Properties Of Solution-processable Organic Blue Fluorescent Materials

This paper design and preparation of a series of blue light emitting materials can solution processing and study their electroluminescent performance.A series of novel bipolar compounds consisting of 4-?9H-carbazole-9-yl?aniline moiety as the electron-donating unit and the isomers of meta-or para-linked S,S-dioxidedibenzothiophene?SO?unit as the electron-withdrawing unit were designed and synthesized.These compounds exhibited obvious intramolecular charge transfer effects as observed in the photoluminescent spectra.All compounds exhibited good thermal properties with glass transition temperatures higher than 110 ?.The UV-vis absorption and photoluminescent spectra,and electrochemical properties can be dramatically affected by the isomers of the SO unit and the incorporated alkylfluorene unit between the SO unit and N-atoms in the 4-?9H-carbazole-9-yl?aniline moiety.These compounds exhibited moderated electroluminescent properties with the best device performances attained based on compound M-3,which exhibited a peak luminous efficiency of 5.6 cd A–1 and a luminescence of 16390 cd m^-2 with a turn on voltage of 2.4 V and CIE coordinates of?0.31,0.58?.By physical doping method,the polymer PFSO50 was doped into polymer PFO,doping ratios were 0.1%,0.5%,1%,3% and 5%,We hope that through physical doping method can introduve more ?-phase.Through the UV-vis absorption spectra and PL spectra in film,we found that the UV-vis absorption spectrum of blend film were not observed at 437 nm ?-phase which is the characteristic absorption peak of ?-phase.At the same time,the PL spectra of blend film also can not observed at 436,462 and 497 nm which is the characteristic emission peak of ?-phase.According to physical doping method,we failed to induce the ?-phase of PFO.Two novel fluorene-based blue-light emitting copolymers consisting of aromatic carbazole or dibenzothiophene-S,S-dioxide?SO?moiety in side chain are designed and synthesized based on a palladium-catalyzed Suzuki polymerization.The UV-vis absorption,photoluminescence characteristics and X-ray diffraction measurement of the resulting copolymers demonstrate that the incorporation of such aromatic units can promote the formation of the ?-phase.The resulting copolymers consisting of aromatic units exhibit improved electroluminescence properties relative to the pristine PFO film.A maximum luminous efficiency of 2.25 cd A^-1 with Commission Internationale de l'Eclairage coordinates of?0.17,0.09?is obtained from the light-emitting device based on the copolymer consisting of SO unit?PFO-SO?.A series of small molecules were made based on naphthalene-indene-fluorene?NIF?unit,compound BD1 due to the o-methyl in amino,which make it a large dihedral angle between diphenylamine and naphthalene and the emission spectra is blue shift.Compound BD1,BD2,BD3 and BD4 decomposition temperature?Td,loss of weight 5%?are more than 400 ?,which shows that the target compounds have a good thermal stability.Device structure: ITO/MeO-TPD:F4-TCNQ?1500 ?,4%?/NPB?200 ??/ADN:BD3?250 ?,x%?/Bebq2?250 ??/Li F?10 ??/Al.The device with 7% BD3 as dopant has the best device performance,maximum lumen efficiency 11.0 cd A^-1,commission Internationale del' Eclairage coordinates of?0.14,0.22?,the power efficiency 9.2 lm/w.A series of solution processing polymers PPF-F,PPF-IF and PPF-NF based on luxuriant,indene-fluorene and naphthalene-indene-fluorene were designed and synthesized,and device structure: ITO/PEDOT:PSS?40 nm?/Emitter?80 nm?/CsF?1.5 nm?/Al?80 nm?,the polymers of PPF-F,PPF-IF and PPF-NF were uced as light emitting layer of electroluminescent devices,the polymer PPF-F has the best device performance,the maximum lumen efficiency 1.5 cd A^-1,commission Internationale del' Eclairage coordinates of?0.14,0.16?,the maximum brightness of 5765 cd m^-2.