含铱配合物的聚对苯类电磷光聚合物

通过Suzuki聚合法合成了以聚对苯为主链的含铱配合物的电磷光共轭聚合物。部分苯环单元被β-二酮结尾的烷氧基链取代,进而与2-苯基吡啶配位形成悬垂的铱配合物侧链。宽带隙的聚对苯主链使主体与客体的能级匹配,从而有利于能量的转移。铱配合物通过长β-二酮结尾的烷氧基链悬挂在聚对苯的侧链上提高了聚合物的溶解性,有利于器件的制作。另外,由于连在氧原子上的β-二酮具有较大的旋转自由度,增大了β-二酮的反应活性有利于配位反应的进行。聚合物的EL光谱只显示客体铱配合物的发射,主体的发射已被完全猝灭。这表明聚合物主体和铱配合物客体之间发生了有效的能量转移。PPPIrPPy2聚合物发光器件的EL光谱发光波长为525nm,最大外量子效率为2.6%。

Electrophosphorescent Polymers Based on Poly(para-phenylene)s Grafted with Ir Complex on Side Chain

Electrophosphorescent light-emitting diodes,for which both singlet and triplet excitons contribute to the light emission,have attracted great scientific and commercial attention because of their high quantum efficiency.Iridium-based complexes are the popular selection as the efficient dopant due to a relatively short phosphorescent lifetime.Aseries of electrophosphorescent conjugated polymers based on substituted para-polyphenylenes are synthesized by Suzuki polycondensation.Apart of N-alkyl benzene units were replaced by di-ketone group ended to provide a ligand for the formation of Ir complexes in side chain in the presence of 2-phenylpyridine.Poly (para-phenylene) with broad band gap makes the energy level better matching between the host and the guest.Therefore,energy transfer from the host to Ir-complex becomes more efficient.The incorporation of long alkoxy group into the side-chain can substantially raise the flexibility of polymer that leads to the improvement of solubility of polymer,which is helpful for the fabrication of devices.On the other hand,the activity of β-diketone group to iridium core is raised due to more rotating freedom of β-diketone-alkyl around the oxygen atom.ELemission from the backbone of the polymers is completely quenched even though the feed content ratio of Ir-complex is as low as 1%.They all show only the emission from iridium complex,while the host emission disappeared.It indicates that efficient energy transfer from the main chain to the Ir-complex occurs.The maximum external quantum efficiency of 2.6% was achieved for PPPIrPPy2 with the feed content ratio of Ir-complex of 2% at the current density of 0.35 mA/cm².