Synthesis and Properties of Triazine Derivatives as Bipolar Host Materials for Blue Phosphorescent Organic Light-emitting Diodes

doi:10.7517/j.issn.1674-0475.2015.06.479

Abstract

Abstract:

A novel phosphorescent host materials, 9-(4-(4,6-di-α-naphthoxy-1,3,5-triazin-2-yl) phenyl) carbazole (NOTPC), was designed and synthesized, and its structure was characterized by means of IR,¹HNMR, ¹³CNMR and elemental analysis. The photophysical properties and energy-level structure of NOTPC were studied by ultraviolet-visble (UV-Vis) absoption, fluorescence, phosphorescent spectroscopies at 77 K, cyclic voltammetry (CV), thermogravimetric analysis(TGA), differential scanning calorimetry (DSC) and calculated by density functional theory(DFT). The results show that the maximum absorption wavelengths are located at about 290 nm, 340 nm in dilute CH₂Cl₂solution. NOTPC can emit blue fluorescence at 390 nm, 472 nm in dilute CH₂Cl₂solution, and exhibits blue phosphorescent emission at 452 nm and its triplet state energy (E_T) is estimated to be 2.80 eV. NOTPC can be used as host material for the blue emitter bis(4,6-difluorophenylpyridine)(picolinate)(Ⅲ) (Firpic) in PhOLED. DFT theoretical calculation reveals that the highest occupied molecular orbital (HOMO) of NOTPC is mainly distributed on N-phenly carbazole moiety, while the lowest unoccupied molecular orbital(LUMO) is mainly dispersed over the triazine moiety. Cyclic voltammetry measurement shows that HOMO energy level of NOTPC is located in -5.40 eV, which matches with the energy levels of ITO(-4.5--5.0 eV); LUMO energy level of NOTPC is located in -2.32 eV, which is close to the energy level of PBD (-2.82 eV). So NOTPC possesses bipolar properties of hole and electron transport, and has good thermal stability.

Key words: triazine, host material, biplor, blue phosphorescent OLEDs

CHEN Yu, LIN Hailang, LIN Zhaoyang, LIU Yajing, ZHAO Xin. Synthesis and Properties of Triazine Derivatives as Bipolar Host Materials for Blue Phosphorescent Organic Light-emitting Diodes[J]. Imaging Science and Photochemistry, 2015, 33(6): 479-486.

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