Probing the energy levels in hole-doped molecular semiconductors
Probing the energy levels in hole-doped molecular semiconductors
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DOI：
10.1039/c5mh00023h
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发表时间：
2015-06
影响因子：
13.3
通讯作者：
S. Winkler;P. Amsalem;Johannes Frisch;M. Oehzelt;G. Heimel;N. Koch
中科院分区：
文献类型：
--
作者：
S. Winkler;P. Amsalem;Johannes Frisch;M. Oehzelt;G. Heimel;N. Koch
了解极化子（分子半导体中的基本电荷载体）的本质对于以上级（光）电子器件功能为目标的合理材料设计是不可或缺的。传统上设想的对应能级的图像调用半导体的能隙内的单个占据的分子状态。在这里，通过采用相结合的理论和多技术的实验方法，我们表明，这张照片需要修改。在将过量的电子或空穴引入材料中时，相应的前沿分子能级被强烈的原位库仑排斥分裂成上部未占据的子能级和下部占据的子能级，其中只有一个位于半导体带隙内。通过也包括分子离子和周围中性分子之间的位点间库仑相互作用，我们提供了一个完整的图片的电子结构的分子半导体中存在的过剩电荷。有了这样的理解，以前的结果进行了严格的重新检查，并在弱相互作用的分子系统中的极化子的性质和动力学的未来调查奠定了坚实的基础。
Understanding the nature of polarons – the fundamental charge carriers in molecular semiconductors – is indispensable for rational material design that targets superior (opto-) electronic device functionality. The traditionally conceived picture of the corresponding energy levels invokes singly occupied molecular states within the energy gap of the semiconductor. Here, by employing a combined theoretical and multi-technique experimental approach, we show that this picture needs to be revised. Upon introducing an excess electron or hole into the material, the respective frontier molecular level is split by strong on-site Coulomb repulsion into an upper unoccupied and a lower occupied sub-level, only one of which is located within the semiconductor gap. By including also inter-site Coulomb interaction between molecular ions and circumjacent neutral molecules, we provide a complete picture for the electronic structure of molecular semiconductors in the presence of excess charges. With this understanding, a critical re-examination of previous results is called for, and future investigations of the properties and dynamics of polarons in weakly interacting molecular systems are put on sound footing.