一种苯并咪唑类双极性蓝色磷光主体材料的合成及性能

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

设计合成了一种基于苯并咪唑的新型双极性蓝色磷光主体材料1-苯基-2-[4-(N-咔唑基)苯基]苯并咪唑(PCPB),并对其结构进行了表征。通过紫外-可见、荧光、低温磷光光谱以及循环伏安法、热重分析、差热分析和密度泛函理论对其性能及结构进行了研究。结果表明,PCPB在CH2Cl2稀溶液中的吸收峰位于296和368 nm,发射峰位于401nm,属于深蓝色荧光;PCPB的低温(77K)磷光光谱的第一吸收峰位于452nm,其三线态能级为2.74e V,与蓝色磷光材料FIrpic(2.62e V)的能级相匹配;PCPB的HOMO主要分布在苯基咔唑单元,而LUMO主要定域在苯并咪唑环上。其HOMO能级为-5.54e V,与阳极ITO的功函(-4.5^-5.0 e V)相匹配,LUMO能级为-2.68e V,接近于电子传输材料PBD(-2.82e V)。PCPB表现出双极传导性能,且热稳定性良好。

A novel phosphorescent host materials,1-phenyl-2-[4-( N-carbazol-9-yl) phenyl] benzoimidazole( PCPB),was designed and synthesized,and its structure was characterized by1 H NMR and13 C NMR. The photophysical properties and energy-level structure of PCPB were studied by 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 showed that the maximum absorption wavelengths are located at about 296 and 368 nm in dilute CH2Cl2 solution. PCPB can emit navy blue photofluorescence at 401 nm in dilute CH2Cl2 solution,and exhibits blue phosphorescent emission at 452 nm from the highest-energy vibronic subband at 77 K,from which its triplet state energy( ET) is estimated to be 2. 74 e V. PCPB can be used as host material for the blue emitter bis( 4,6-difluorophenylpyridine)( picolinate)( Ⅲ)( Firpic) in Ph OLED. DFT calculation reveals that the highest occupied molecular orbital( HOMO) of PCPB is mainly distributed on N-phenly carzole moiety,while the lowest unoccupied molecular orbital( LUMO) is mainly dispersed over the benzoimidazole moiety. CV measurement shows that HOMO energy level of PCPB is located in- 5. 54 e V,which is matched with the energy levels of ITO; LUMO energy level of PCPB is located in- 2. 68 e V,which is close to the energy level of PBD(- 2. 82 e V). So PCPB possesses bipolar property of hole and electron transport,and has good thermal stability.