Highly Branched Phosphorescent Dendrimers for Efficient Solution‐Processed Organic Light‐Emitting Diodes
Highly Branched Phosphorescent Dendrimers for Efficient Solution‐Processed Organic Light‐Emitting Diodes
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DOI：
10.1002/adfm.200600118
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发表时间：
2007-05
影响因子：
19
通讯作者：
R. N. Bera;N. Cumpstey;P. Burn;I. Samuel
中科院分区：
文献类型：
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作者：
R. N. Bera;N. Cumpstey;P. Burn;I. Samuel
分子间相互作用在有机发光二极管（OLED）的性能中起着至关重要的作用。在这里，我们报道了 fac-tris(2-苯基吡啶基)铱(III)核树枝状聚合物的光物理和电致发光特性，其中高度支化的联苯树枝状聚合物用于控制分子间相互作用。芴表面基团的存在提高了溶解度并提高了光致发光的效率，尤其是在固态下。该树枝状聚合物的发射峰约为 530 nm，溶液中的 PL 量子产率为 76%，薄膜中的 PL 量子产率为 25%。该树枝状聚合物的光物理性质与具有相同结构但不含芴表面基团的类似树枝状聚合物进行了比较。树枝状聚合物 LED (DLED) 是使用每种树枝状聚合物作为磷光发射体混合在 4,4'-双(N-咔唑基)联苯主体中制备的。通过加入 1,3,5-三(2-N-苯基苯并咪唑基)苯电子传输层，器件性能得到显着提高。在双层 LED 中，没有表面基团的树枝状聚合物的峰值外部量子效率为 10% (38 Cd A-1)，而具有芴表面基团的树枝状聚合物的峰值外部量子效率为 13% (49.8 Cd A-1)。
Intermolecular interactions play a crucial role in the performance of organic light‐emitting diodes (OLEDs). Here we report the photophysical and electroluminescence properties of a fac‐tris(2‐phenylpyridyl)iridium(III) cored dendrimer in which highly branched biphenyl dendrons are used to control the intermolecular interactions. The presence of fluorene surface groups improves the solubility and enhances the efficiency of photoluminescence, especially in the solid state. The emission peak of the dendrimer is around 530 nm with a PL quantum yield of 76 % in solution and 25 % in a film. The photophysical properties of this dendrimer are compared with a similar dendrimer with the same structure but without the fluorene surface groups. Dendrimer LEDs (DLEDs) are prepared using each dendrimer as a phosphorescent emitter blended in a 4,4′‐bis(N‐carbazolyl)biphenyl host. Device performance is improved significantly by the incorporation of an electron‐transporting layer of 1,3,5‐tris(2‐N‐phenylbenzimidazolyl)benzene. A peak external quantum efficiency of 10 % (38 Cd A–1) for the dendrimer without surface groups and 13 % (49.8 Cd A–1) for the dendrimer with fluorene surface groups is achieved in the bilayer LEDs.