高效率共轭聚合物主体绿光磷光发光二极管

因电致发光效率高和器件制备工艺简单，聚合物为主体的绿色磷光电致发光成为一个研究热点.共轭聚合物的三线态能级一般低于绿色磷光材料的三线态能级，易对磷光的发光引起猝灭导致低的发光效率，所以较少被用作绿色磷光材料的主体.通过增加聚乙烯基咔唑（PVK）作为空穴传输层，获得了高发光效率的共轭聚合物聚芴（PFO）作主体绿色磷光发射，甚至高于相同条件下以PVK为主体的绿色磷光发射.究其原因，PVK的电子阻挡作用使发光中心靠近PVK与PFO的界面，界面处PVK因为其高的三线态能级增强了绿色磷光的发光.当三-（2-苯基吡啶）-Ir（Ir（ppy）₃）掺杂浓度为2％时得到了最高的亮度效率24.8 cd/A，此时的电流密度为4.65 mA/cm²，功率效率为11 lm/W，最高亮度达到35054 cd/m²，色坐标是（0.39，0.56）. 关键词： 共轭聚合物 磷光 绿光发光

High efficiency phosphorescence light-emitting diodes with conjugated polymer host

Polymer hosted phosphorescent light-emitting diodes (PLEDs) were attractive because of their high efficiency light-emission and easy fabrication technology using solution process. For green phosphorescence PLEDs,non-conjugated polymer,such as poly (iV-vinylcarbazole) (PVK),were often used as host; while conjugated polymer have been proved to quench phosphorescence emission because of their low-lying triplet energy level. In this article, high efficiency phosphorescent green-emission was obtained with conjugated polymer of poly (9, 9-dioctylfluorene) ( PFO) as host using the device structure of ITO/poly (ehtlenedioxythiophene): poly (styrene sulfonic acid) (PEDOT: PSS) (50 nm)/PVK (40 nm)/emissive layer (EML) (80 nm)/ Ba (4 nm)/Al (150 nm) . The EML were PFO doped with different concentration of fac-tris (2-phenylpyridine) indium ( Ⅲ ) (Ir (ppy)_3) in weight. The PLED with 2 wt% Ir(ppy)_3 demonstrated the maximum luminous efficiency of 24.8 cd/A at current density of 4.65 mA/cm~2 and power efficiency of 11 lm/w with the peak emission at 520 nm. The luminance reached 35054 cd/ m~2 at the current density of 265 mA/cm~2. According to analyzsis, the hole transport layer PVK can play important role in obtaining highly efficient green light emissing, whose electrons blocking effect resulted in the interfacial emissing center, and then the interfacial PVK enhanced green emission through energy transfer due to its high triplet enery level.