Synthesis and Exciton Dynamics of Donor-Orthogonal Acceptor Conjugated Polymers: Reducing the Singlet-Triplet Energy Gap
Synthesis and Exciton Dynamics of Donor-Orthogonal Acceptor Conjugated Polymers: Reducing the Singlet-Triplet Energy Gap
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DOI：
10.1021/jacs.7b03327
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发表时间：
2017-08-16
影响因子：
15
通讯作者：
Bronstein, Hugo
中科院分区：
文献类型：
--
作者：
Freeman, David M. E.;Musser, Andrew J.;Bronstein, Hugo
能量低的三重态的存在是有机半导体的一个标志。尽管它们呈现出丰富有趣的光物理特性，但这些光学暗态显着限制了光电器件的性能。发射电荷转移分子的最新进展开辟了减少三重态和“明亮”单线态之间能量差距的途径，允许它们之间的热人口交换，并消除了设备中的重要损失通道。在共轭聚合物中，这种间隙已被证明是耐改性的。在这里，我们介绍了一种在完全共轭聚合物中减小单线态三重态能隙的一般方法，使用供体-正交受体基序来空间分离电子和空穴波函数。这种新一代共轭聚合物可以大大降低交换能，增强三重态形成并使热激活的延迟荧光成为可能。我们发现这两个过程的机制都是由pi-pi*和电荷转移态之间的激发态混合驱动的，这为反向系统间交叉提供了新的见解。
The presence of energetically low-lying triplet states is a hallmark of organic semiconductors. Even though they present a wealth of interesting photophysical properties, these optically dark states significantly limit optoelectronic device performance. Recent advances in emissive charge transfer molecules have pioneered routes to reduce the energy gap between triplets and "bright" singlets, allowing thermal population exchange between them and eliminating a significant loss channel in devices. In conjugated polymers, this gap has proved resistant to modification. Here, we introduce a general approach to reduce the singlet triplet energy gap in fully conjugated polymers, using a donor-orthogonal acceptor motif to spatially separate electron and hole wave functions. This new generation of conjugated polymers allows for a greatly reduced exchange energy, enhancing triplet formation and enabling thermally activated delayed fluorescence. We find that the mechanisms of both processes are driven by excited-state mixing between pi-pi* and charge-transfer states, affording new insight into reverse intersystem crossing.