We report the site-specific probing of charge-transfer dynamics in a prototype system for organic photovoltaics (OPV) by picosecond time-resolved X-ray photoelectron spectroscopy. A layered system consisting of approximately two monolayers of C60 deposited on top of a thin film of Copper-Phthalocyanine (CuPC) is excited by an optical pump pulse and the induced electronic dynamics are probed with 590 eV X-ray pulses. Charge transfer from the electron donor (CuPC) to the acceptor (C60) and subsequent charge carrier dynamics are monitored by recording the time-dependent C 1s core level photoemission spectrum of the system. The arrival of electrons in the C60 layer is readily observed as a completely reversible, transient shift of the C60 associated C 1s core level, while the C 1s level of the CuPC remains unchanged. The capability to probe charge transfer and recombination dynamics in OPV assemblies directly in the time domain and from the perspective of well-defined domains is expected to open additional pathways to better understand and optimize the performance of this emerging technology.
@article{arxiv.1503.05353,
title = {Site-specific probing of charge transfer dynamics in organic photovoltaics},
author = {Tiberiu Arion and Stefan Nepp and Friedrich Roth and Andrey Shavorskiy and Hendrik Bluhm and Zahid Hussain and Oliver Gessner and Wolfgang Eberhardt},
journal= {arXiv preprint arXiv:1503.05353},
year = {2015}
}