高效白色磷光有机电致发光器件

采用真空热蒸镀方法以4,4'-bis (carbazol-9-yl) biphenyl (CBP)为主体材料、以bis[2-(4-tert-butylphenyl) benzothiazolato-N,^C2] iridium (acetylacetonate) [(t-bt)₂Ir(acac)]磷光染料为掺杂剂构成黄色发光层, 制备了高效白光的有机电致发光器件(OLEDs). OLEDs的器件结构为indiumtin oxide (ITO)/N,N’-bis-(1-naphthyl)-N,N’-biphenyl-1,1’-biphenyl-4,4’-diamine (NPB)/CBP: (t-bt)₂Ir (acac)/NPB/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/8-hydroxy quinoline aluminum(Alq₃)/Mg:Ag, 从ITO阳极开始的第一层NPB为空穴传输层, 第二层超薄的NPB为蓝色发光层, BCP为空穴阻挡层和激子阻挡层, Alq₃为电子传输层. 结果表明, 器件电压在3 V启亮, 在16.5 V时, 器件的最高亮度达到15460 cd·m^-2; 在4 V时, 器件达到最大流明效率为7.5 lm·W^-1, 器件启亮后所发出的白光光谱在低电压时随电压变化有稍微的移动, 但是都在白光范围内变化. 在电压达到8 V后Commission Internationale I’Eclairage(国际照明委员会) (CIE)色坐标为(0.33, 0.32), 并且光谱及色坐标稳定, 不随电压变化而改变, 与最佳的白光坐标(0.33, 0.33)几乎重合. 同时, 从机理上解释了光谱移动和效率衰减的原因, 并探讨了载流子陷阱和能量传递的关系.

High-efficiency White Phosphorescent Organic Light-Emitting Diodes

High-efficiency white organic light-emitting devices (WOLEDs) based on phosphorescent dye bis[2-(4-tert-butylphenyl)benzothiazolato-N,C^2’]iridium (acetylacetonate) [(t-bt)₂Ir (acac)] doped 4,4’-bis (carbazol-9-yl) biphenyl (CBP) as a yellow emitting layer were fabricated. The structure of the devices is indium tin oxide (ITO)/N,N’-bis-(1-naphthyl)-N,N’-biphenyl-1,1’-biphenyl-4,4’-diamine (NPB)/CBP: (t-bt)₂Ir(acac)/NPB/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/8-hydroxyquinoline aluminum(Alq₃)/Mg:Ag, and the second NPB layer fromthe anode was used as a blue fluorescent emitter and the first NPB layer was used as a hole transporting layer, the BCP and Alq₃ were used as hole blocking and electron transporting layers, respectively. The turn-on voltage of the device was 3 V with a maximumluminance of 15460 cd·m^-2 at 16.5 V and maximumluminance efficiency of 7.5 lm·W^-1 at 4 V, respectively. The Commission Internationale de I’Eclairage (CIE) coordinates located at (0.33, 0.32) remained stable at the driving voltage higher than 8 V, which is almost consistent with the optimum white CIE of (0.33, 0.33). The purity of white light could be adjusted by doping concentration. The effect of charge carrier trapping and energy transfer on the device performance were also discussed.