Synthesis And Characterization Of Blue Fluorescent Materials Based On Anthracene Derivative With Cyclic Phosphazenes Cores

Organic electroluminescent materials are the basis of OLED devices.The properties of electroluminescent materials can largely determine the color purity,luminous efficiency,lifespan and stability of electroluminescent devices.Among the primary-color luminescent materials,the blue emitters generally show a noticeably inferior electroluminescence(EL)performance with regard to efficiencies,lifespan and color quality.Therefore,the design and preparation of high efficiency,high color purity and high stability blue emitters is of great significance for the development of OLED technology.Two novel solution processable anthracene derivatives(HCCPAn and HCCPAnT)based on cyclic phosphazenes cores have been designed and synthesized to be used as deep-blue emitters in blue OLED devices.The structures of these emitters were well confirmed by proton nuclear magnetic resonance(~1H NMR)and MALDI-TOF-MS.These two compounds show very high decomposition temperatures at 430.9?and342.9?,respectively.Especially,the glass transition temperature(Tg)of the compound HCCPAnT is increased up to 252?.Both the starburst materials exhibit good film-forming capabilities and display deep blue emission both in solution and in the thin solid film.The PL quantum yield of the compound HCCPAn and HCCPAnT were determined both to be 49%,using quinine sulphate as the standard.To investigate the electrochemical properties of compound HCCPAn and HCCPAnT,cyclic voltammetry was carried out.The HOMO levels for compound HCCPAn and HCCPAnT were determined both to be-5.561eV,the LUMO levels were-2.591eV and-2.491eV,respectively.And,From the difference between the HOMO level and the LUMO level,the band gaps for HCCPAn and HCCPAnT were determined to be2.97eV and 3.07eV respectively,which indicates both HCCPAn and HCCPAnT are wide band gap semiconducting materials.The excellent solubility,deep blue emission,and good film-forming ability enable the compound HCCPAn and HCCPAnT to be used as the blue emitters in electroluminescent devices.To investigate the electroluminescence properties of compound HCCPAn and HCCPAnT as emissive layer materials for fluorescence OLEDs,non-doping electroluminescent devices with the simple configuration of ITO/PEDOT/PVK/emitter:compound HCCPAn or HCCPAnT/TPBI/CsF/Al were fabricated and characterized.The device based on HCCPAn shows a maximum brightness of 566cd/A,current efficiency(CE)of 0.18 cd/A and the turn-on voltage of4V.The device based on HCCPAnT shows a maximum brightness of 553cd/A,current efficiency(CE)of 0.16 cd/A and the turn-on voltage of 4V.The CIE coordinates for the devices based on compound HCCPAn and HCCPAnT are(0.15,0.06)and(0.15,0.07)respectively,which is close to the blue standards(0.14,0.08)of NTSC.