Suppression of green emission in a new class of blue-emitting polyfluorene copolymers with twisted biphenyl moieties
Suppression of green emission in a new class of blue-emitting polyfluorene copolymers with twisted biphenyl moieties
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DOI：
10.1002/adfm.200400457
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发表时间：
2005-06-01
影响因子：
19
通讯作者：
Cacialli, F
中科院分区：
文献类型：
--
作者：
Lim, SF;Friend, RH;Cacialli, F
基于聚芴的蓝色发光聚合物的颜色纯度通常被“长波长”绿色发射带损害，这首先归因于聚合物链间物质，最近归因于发射性芴酮检测物的形成。在这里，我们研究的性质和抑制这样的频带通过表征一类新的聚芴衍生物的改性通过插入官能团在桥接点（位置C9），以增加环间扭转角。我们发现，改性聚芴和均聚物的无规共聚物的固态光致发光光谱显示出一个渐进的减少，他的长波长发射。电致发光光谱还显示出在具有40%或更大的“扭曲”共聚单体单元的浓度的共聚物中有效抑制这样的谱带。模型低聚物的量子化学计算解决的影响的桥接单元上的扭转角，和由此产生的激发态的属性，对分子堆积的影响也探讨了力场计算。我们的结论是内联苯扭转角的增加是一个可行的策略，抑制长波长发射带的聚芴。
The color purity of polyfluorene-based blue-emitting polymers is often compromized by "long-wavelength" green emission bands, attributed to polymer interchain species first and more recently to formation of emissive fluorenone detects. Here we study the nature and the suppression of such bands via characterization of a new class of polyfluorene derivatives modified by insertion of functional groups at the bridging points (position C9), so as to increase inter-ring torsion angles. We find that the solid-state photoluminescence spectra of random copolymers of the modified polyfluorenes and the homopolymer display a progressive decrease of he long-wavelength emission. Electroluminescence spectra also show efficient suppression of such bands in the copolymers with a concentration of 'twisted' comonomer units of 40% or greater. Quantum-chemical calculations on model oligomers address the influence of the bridging unit on the torsion angles, and the resulting excited-state properties, the impact on molecular packing is also explored with force-field calculations. We conclude that increase of intra-biphenyl torsion angles is a viable strategy for suppression of long-wavelength emission bands in polyfluorenes.