Quantum coherence controls the charge separation in a prototypical artificial light-harvesting system

Abstract

The efficient conversion of light into electricity or chemical fuels is a fundamental challenge for sustainable development. In artificial photosynthetic and photovoltaic devices this conversion is generally thought to happen on the femtosecond time scale and to involve an incoherent electron transfer process. In some natural biological systems, however, there is now growing evidence that the coherent motion of electronic wavepackets is an essential primary step, raising questions about the role of quantum coherence in artificial devices. Here we investigate the primary charge transfer process in a supramolecular triad, a prototypical artificial reaction center. Combining high time-resolution femtosecond spectroscopy and time-dependent density functional theory, we provide compelling evidence that the driving mechanism of the photoinduced current generation cycle is a correlated wavelike motion of electrons and nuclei on the timescale of few tens of femtoseconds. We highlight the fundamental role of the interface between chromophore and charge acceptor in triggering the coherent wavelike electron-hole splitting.