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

doi:10.7517/j.issn.1674-0475.2016.04.355

Abstract

Abstract:

A novel phosphorescent host material functionalized with bicarbazole and phosphine oxides, 6,6'-Bis(diphenyl-phosphinoyl)-9,9'-dihexyl-3,3'-bicarbazole (DPDBC), was designed and synthesized. The structure was characterized by means of ¹HNMR, ¹³CNMR, IR and HRMS. The photophysical properties and energy level structure of DPDBC were studied by ultraviolet-visble (UV-Vis) absorption, fluorescence, phosphorescent spectroscopies at 77 K, cyclic voltammetry (CV), thermogravimetric analysis(TGA), differential scanning calorimetry (DSC) and density functional theory(DFT). The results show that it has two absorption lands in dilute CH₂Cl₂ solution. The maximum absorption wavelength locates at 306 nm. DPDBC can emit blue photofluorescence at 420 nm in dilute CH₂Cl₂ solution, and exhibit phosphorescent emission at 447 nm from the highest energy vibronic subband at 77 K, from which the triplet state energy (E_T) is estimated to be 2.77 eV. DPDBC can be used as host material for the blue emitter FIrpic in PhOLED. Cyclic voltammetry measurement shows that the HOMO energy level of DPDBC locates at -5.48 eV, which matches the energy levels of ITO; the LUMO energy level of DPDBC locates at -2.36 eV, which is close to the energy level of PBD (-2.82 eV). So as a host material for blue phosphorescent organic light-emitting diodes, DPDBC possesses bipolar properties of hole and electron transport, and has good thermal stability.

Key words: bicarbazole, phosphine oxide, bipolar, blue phosphorescent

CHEN Yu, ZHANG Qiang, LIU Yajing, YANG Shuangshuang, ZHAO Xin. Synthesis and Properties of Bicarbazole Derivatives as Bipolar Host Materials for Blue Phosphorescent Organic Light-emitting Diodes[J]. Imaging Science and Photochemistry, 2016, 34(4): 355-363.

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