Tenopala-Carmona Francisco, Hertel Dirk, Hillebrandt Sabina, Mischok Andreas, Graf Arko, Weitkamp Philipp, Meerholz Klaus, Gather Malte C
Humboldt Centre for Nano- and Biophotonics and Institute of Physical Chemistry, Department of Chemistry, University of Cologne, Köln, Germany.
Organic Semiconductor Centre, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, UK.
Nat Commun. 2023 Oct 2;14(1):6126. doi: 10.1038/s41467-023-41841-2.
The orientation of luminescent molecules in organic light-emitting diodes strongly influences device performance. However, our understanding of the factors controlling emitter orientation is limited as current measurements only provide ensemble-averaged orientation values. Here, we use single-molecule imaging to measure the transition dipole orientation of individual emitter molecules in a state-of-the-art thermally evaporated host and thereby obtain complete orientation distributions of the hyperfluorescence-terminal emitter C545T. We achieve this by realizing ultra-low doping concentrations (10 wt%) of C545T and minimising background levels to reliably measure its photoluminescence. This approach yields the orientation distributions of >1000 individual emitter molecules in a system relevant to vacuum-processed devices. Analysis of solution- and vacuum-processed systems reveals that the orientation distributions strongly depend on the nanoscale environment of the emitter. This work opens the door to attaining unprecedented information on the factors that determine emitter orientation in current and future material systems for organic light-emitting devices.
有机发光二极管中发光分子的取向对器件性能有很大影响。然而，由于目前的测量仅提供总体平均取向值，我们对控制发射体取向的因素的了解有限。在这里，我们使用单分子成像来测量最先进的热蒸发主体中单个发射体分子的跃迁偶极矩取向，从而获得超荧光末端发射体C545T的完整取向分布。我们通过实现C545T的超低掺杂浓度（10 wt%）并将背景水平降至最低来可靠地测量其光致发光，从而实现这一目标。这种方法在与真空处理器件相关的系统中产生了1000多个单个发射体分子的取向分布。对溶液处理和真空处理系统的分析表明，取向分布强烈依赖于发射体的纳米级环境。这项工作为获取有关当前和未来有机发光器件材料系统中决定发射体取向的因素的前所未有的信息打开了大门。
