Porphyrin-cored star polymers as efficient nondoped red light-emitting materials
Porphyrin-cored star polymers as efficient nondoped red light-emitting materials
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DOI：
10.1021/ma051610s
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发表时间：
2006
期刊：
影响因子：
5.5
通讯作者：
Binsong Li;Xinjun Xu;Minghao Sun;Yaqin Fu;G. Yu;Yunqi Liu;Zhishan Bo
中科院分区：
文献类型：
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作者：
Binsong Li;Xinjun Xu;Minghao Sun;Yaqin Fu;G. Yu;Yunqi Liu;Zhishan Bo
有机和聚合物发光二极管（OLED和PLED）由于其高亮度、低工作电压、快速响应和成本有效的溶液可加工性而在大面积平板显示器中引起了极大的兴趣。1对于全色显示器，需要三种原色，即蓝色、绿色和红色。只有绿色发光材料才能完全满足商业应用的要求。2.蓝光发光材料已经取得了很高的发光效率和亮度，但存在的主要问题是稳定性和寿命。红光发射通常通过将红色染料如卟啉、3含吡喃化合物、4和铕螯合物5掺杂到宽带隙主体材料中来实现。然而，最佳掺杂剂浓度通常很低，并且有效掺杂范围很窄。4a掺杂的红色染料在较高的掺杂浓度下容易聚集在固体膜中，这通常导致其荧光自猝灭，从而导致器件的效率降低。在较低的掺杂浓度下，从主体材料到客体（红色染料）的能量传递通常是不完全的，这导致器件的色纯度差。此外，对于实际应用，基于掺杂剂的LED比基于未掺杂的主发射器的LED更难以适应大规模生产工艺。7.在我们的前期工作中，制备了一系列结构清晰、单分散的卟啉核星形低聚物，作为一种非掺杂的红色发光分子材料，并研究了它们的吸收和光致发光性质。8这些单分散低聚物在普通有机溶剂中表现出良好的溶解性和高量子产率。然而，制备单分散的、结构清晰的星形低聚物通常是耗时的，并且在每个步骤中通常需要柱层析纯化。制备的困难限制了它们作为材料的使用。为了实际应用，迫切需要低成本的大规模合成。在这里，我们报道了一种简单的一锅法制备卟啉核星星聚合物及其光致和电致发光性能的研究。此外，为了提高卟啉核星星聚合物的空穴传输能力和热稳定性，引入了三苯胺（TPA）作为端基。9.循环伏安法测试表明，TPA封端的星星卟啉具有比芴封端的星星卟啉更高的HOMO能级。TPA末端基团的引入还降低了空穴从ITO注入到星星卟啉层的能垒。
Organic and polymeric light-emitting diodes (OLEDs and PLEDs) have attracted tremendous interest in the large-area flatpanel displays due to their high brightness, low operation voltage, fast response, and cost-effective solution processability. 1 For the full-color displays, three primary colors, ie, blue, green, and red, are required. Only the green light-emitting materials fully meet the requirements for the commercial applications. 2 For the blue light-emitting materials, high brightness and efficiency have been achieved, and the main problems are their stabilities and lifetimes. Red light-emitting is usually achieved by doping the red dyes such as porphyrins, 3 pyran-containing compounds, 4 and europium chelate complexes5 into the wideband-gap host materials. However, the optimum dopant concentration is usually very low and the effective doping range is very narrow. 4a The doped red dyes are prone to aggregation in solid film at higher doping concentration, which usually leads to self-quenching of their fluorescence and results in lower efficiency for the devices. At lower doping concentration, the energy transfer from the host materials to the guest (red dyes) is often incomplete, which brings about poor color purity for the devices. 4b, 6 Furthermore, for the practical application, LEDs based on dopant are more difficult to adapt for mass production processes than those based on a nondoped host emitter. 7 In our previous paper, a set of well-defined and monodisperse porphyrin-cored star-shaped oligomers, as a kind of nondoped red-emissive molecular materials, were prepared, and their absorption and photoluminescence properties were investigated. 8 These monodisperse oligomers exhibited good solubility in common organic solvents and high quantum yields. However, the preparation of the monodisperse, well-defined star-shaped oligomers was usually time-consuming, and the column chromatography purification was usually required in each step. The difficulty of preparation limited them to be used as materials. For practical application, a low-cost large-scale synthesis is urgently required. Here, we report a simple one-pot approach to prepare porphyrin-cored star polymers and the investigation of their photo-and electroluminescent properties. Furthermore, to improve the hole transfer ability and the thermal stability of the porphyrin-cored star polymers, triphenylamine (TPA) was introduced as the end groups. 9 The cyclic voltammetry measurements indicated that the TPA-capped star porphyrin had higher HOMO energy level than the fluorene-capped star porphyrin did. The introduction of TPA end groups also reduced the energy barrier for the hole injection from ITO to the star porphyrin layer.