High-efficiency saturated red light-emitting polyelectrolytes and their neutral precursors: aminoalkyl-substituted polyfluorenes (PFN) with different 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DBT) contents were synthesized by Suzuki coupling reaction. Their quaternized ammonium polyelectrolyte derivatives were obtained through a post-polycondensation treatment on the terminal amino groups. The resulting copolymers are soluble in polar solvents. Narrow band-gap (NBG) DBT units incorporated into the polymer backbone act as exciton traps. As a result, all the polymers emit red light specific to the DBT segments under UV excitation in the solid state. It was found out that the PFN–DBT copolymers show good device performance when high work-function metals, such as Al, are used as the electron-injection cathode replacing conventional low work-function cathodes such as Ca and Ba. It has been shown that these polymers also can be used as electron injection layers (ETL) in double layer structures in polymer light-emitting diodes (PLEDs). Double layer devices, with PFN–DBT as an electron injection layer on top of conventional RGB light-emitting polymers, with high work-function metal cathodes emit light exclusively from the RGB polymers and show high external quantum efficiency.
通过铃木偶联反应合成了高效饱和红色发光聚电解质及其中性前体:具有不同 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DBT) 含量的
氨基烷基取代聚
芴 (PFN)。通过对末端
氨基进行缩聚后处理,得到了它们的季
铵化聚电解质衍
生物。所得共聚物可溶于极性溶剂。聚合物骨架中的窄带隙(NBG)DBT 单元可作为激子陷阱。因此,在固态紫外线激发下,所有聚合物都会发出 DBT 段特有的红光。研究发现,当使用 Al 等高功函数
金属取代 Ca 和 Ba 等传统低功函数阴极作为电子注入阴极时,PFN-DBT 共聚物显示出良好的器件性能。研究表明,这些聚合物还可用作聚合物发光二极管(PLED)双层结构中的电子注入层(ETL)。在传统的 RGB 发光聚合物上使用 PFN-DBT 作为电子注入层的双层装置,其高功函数
金属阴极只从 RGB 聚合物发光,并显示出很高的外部量子效率。