Exciton lifetimes play a critical role in the performance of organic optoelectronic devices. In this work, we investigate how the presence of multiple rotational domains, and therefore grain boundaries, impacts exciton dynamics in thin films of C60/Au(111) using time and angle-resolved photoemission spectroscopy (TR-ARPES). We find that films with multiple rotational domains exhibit shorter exciton lifetimes and evidence of exciton-exciton annihilation, even when one domain predominates. Scanning tunneling microscopy (STM) measurements reveal electronic structure changes resulting from a locally reduced dielectric constant at grain boundaries, providing a mechanism for lifetime reduction through exciton funneling and other additional decay channels. These findings highlight the critical role of film quality in determining intrinsic exciton lifetimes, and show that minuscule amounts of disorder that are nearly undetectable by ensemble measurements can significantly impact dynamics. These results imply that precise structural control is essential for optimize the performance of organic optoelectronic devices.
@article{arxiv.2507.00323,
title = {Quenching of excitons at grain boundaries in C60 thin films},
author = {Rysa Greenwood and Bradley G. Guislain and MengXing Na and Alexandra B. Tully and Sergey Zhdanovich and Jerry Icban Dadap and Sydney K. Y. Dufresne and Vanessa King and Jiabin Yu and Giorgio Levy and Arthur K. Mills and Matteo Michiardi and Andrea Damascelli and Sarah A. Burke and David J. Jones},
journal= {arXiv preprint arXiv:2507.00323},
year = {2025}
}