Transient Monolayer Structure of Rubrene on Graphite: Impact on Hole–Phonon Coupling

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• 作者：Yang He ; Fabio Bussolotti ; Qian Xin ; Jinpeng Yang ; Satoshi Kera ; Nobuo Ueno ; Steffen Duhm
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：July 14, 2016
• 年：2016
• 卷：120
• 期：27
• 页码：14568-14574
• 全文大小：422K
• 年卷期：0
• ISSN：1932-7455

文摘

Charge transport in molecular thin films is often dominated by incoherent hopping processes, and charge-carrier phonon coupling plays a major role in defining mobilities. Our high resolution angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) study reveals the influence of molecular configuration and packing on the hole-phonon coupling in vacuum-sublimed thin films of rubrene on graphite and allows determining charge reorganization energies. In the contact layer to the substrate rubrene is well-ordered with, for low coverages, the tetracene backbone being almost parallel to the graphite surface forming a loose-packed monolayer. Increasing the coverage leads to an orientational transition and a more tilted orientation of rubrene in a close-packed monolayer. This transition results in dramatic changes of spectral features in ARUPS including the photoelectron angular distribution of the highest occupied molecular orbital derived intensity. The charge reorganization energy, however, only changes slightly. The transient monolayer structure of rubrene on graphite allows us, thus, to demonstrate that hole-phonon coupling in organic thin films does not depend very critically on the packing structure.