Spin-dependent exciton formation in π-conjugated compounds
Spin-dependent exciton formation in π-conjugated compounds
复制标题
DOI：
10.1038/35101565
复制
发表时间：
2001-10
期刊：
影响因子：
64.8
通讯作者：
Jo S. Wilson;A. S. Dhoot;Alexander J. A. B. Seeley;M. S. Khan;A. Köhler;R. Friend
中科院分区：
文献类型：
--
作者：
Jo S. Wilson;A. S. Dhoot;Alexander J. A. B. Seeley;M. S. Khan;A. Köhler;R. Friend
由有机半导体制成的发光二极管（LED）的效率由注入的电子和空穴的比例决定，所述注入的电子和空穴重新结合以形成发射性自旋单重态而不是非发射性自旋三重态。如果这些状态的形成过程是自旋无关的，那么有机LED的最大效率将被限制在25%。但是最近的报告表明，发射单重态的分数从22%到63%不等，在这里，我们确定的绝对分数的单重态中产生的含铂的共轭聚合物及其相应的单体。由铂原子引入的自旋-轨道耦合允许三重态发射，因此可以直接比较单重态和三重态的光学和电学发光。我们发现单体的平均单重态生成分数为22 ± 1%，但聚合物为57 ± 4%。这表明，重组是自旋独立的单体，但自旋依赖的过程，有利于单重态的形成，是有效的聚合物。我们认为，这一过程是交换相互作用的结果，这将在相同的聚合物链上的重叠的电子和空穴波函数在其捕获半径。
The efficiency of light-emitting diodes (LEDs) made from organic semiconductors is determined by the fraction of injected electrons and holes that recombine to form emissive spin-singlet states rather than non-emissive spin-triplet states. If the process by which these states form is spin-independent, the maximum efficiency of organic LEDs will be limited to 25 per cent. But recent reports have indicated fractions of emissive singlet states ranging from 22 to 63 per cent,,,, and the reason for this variation remains unclear. Here we determine the absolute fraction of singlet states generated in a platinum-containing conjugated polymer and its corresponding monomer. The spin-orbit coupling introduced by the platinum atom allows triplet-state emission, so optically and electrically generated luminescence from both singlet and triplet states can be compared directly. We find an average singlet generation fraction of 22 ± 1 per cent for the monomer, but 57 ± 4 per cent for the polymer. This suggests that recombination is spin-independent for the monomer, but that a spin-dependent process, favouring singlet formation, is effective in the polymer. We suggest that this process is a consequence of the exchange interaction, which will operate on overlapping electron and hole wavefunctions on the same polymer chain at their capture radius.