Merino P, Große C, Rosławska A, Kuhnke K, Kern K
Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, Stuttgart 70569, Germany.
Ecole Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland.
Nat Commun. 2015 Sep 29;6:8461. doi: 10.1038/ncomms9461.
Exciton creation and annihilation by charges are crucial processes for technologies relying on charge-exciton-photon conversion. Improvement of organic light sources or dye-sensitized solar cells requires methods to address exciton dynamics at the molecular scale. Near-field techniques have been instrumental for this purpose; however, characterizing exciton recombination with molecular resolution remained a challenge. Here, we study exciton dynamics by using scanning tunnelling microscopy to inject current with sub-molecular precision and Hanbury Brown-Twiss interferometry to measure photon correlations in the far-field electroluminescence. Controlled injection allows us to generate excitons in solid C60 and let them interact with charges during their lifetime. We demonstrate electrically driven single-photon emission from localized structural defects and determine exciton lifetimes in the picosecond range. Monitoring lifetime shortening and luminescence saturation for increasing carrier injection rates provides access to charge-exciton annihilation dynamics. Our approach introduces a unique way to study single quasi-particle dynamics on the ultimate molecular scale.
通过电荷产生和湮灭激子是依赖电荷-激子-光子转换技术的关键过程。有机光源或染料敏化太阳能电池的改进需要在分子尺度上处理激子动力学的方法。近场技术为此发挥了重要作用；然而，以分子分辨率表征激子复合仍然是一个挑战。在这里，我们通过使用扫描隧道显微镜以亚分子精度注入电流，并利用汉伯里·布朗-特威斯干涉测量法测量远场电致发光中的光子相关性来研究激子动力学。可控注入使我们能够在固态C60中产生激子，并让它们在寿命期间与电荷相互作用。我们展示了来自局部结构缺陷的电驱动单光子发射，并确定了皮秒范围内的激子寿命。监测随着载流子注入速率增加而导致的寿命缩短和发光饱和，可获取电荷-激子湮灭动力学信息。我们的方法引入了一种在最终分子尺度上研究单个准粒子动力学的独特方式。
