You are currently viewing the abstract.
View Full TextLog in to view the full text
AAAS login provides access to Science for AAAS members, and access to other journals in the Science family to users who have purchased individual subscriptions.
Register for free to read this article
As a service to the community, this article is available for free. Existing users log in.
More options
Download and print this article for your personal scholarly, research, and educational use.
Buy a single issue of Science for just $15 USD.
Pull, pull, pulling electrons along
Organic photovoltaics operate by transferring charge from a light-absorbing donor material to a nearby acceptor. Falke et al. show that molecular vibrations smooth the way for this charge transfer to proceed. A combination of ultrafast spectroscopy and theoretical simulations revealed an oscillatory signal in a model donor/acceptor blend that implicates carbon-carbon bond stretching in concert with the electronic transition. This vibrational/electronic, or vibronic, process maintains a quantum-mechanical phase relationship that guides the charge more rapidly and directly than an incoherent migration from donor to acceptor.
Science, this issue p. 1001
Abstract
Blends of conjugated polymers and fullerene derivatives are prototype systems for organic photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, we elucidate the initial quantum dynamics of this process. Experimentally, we observed coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with first-principle theoretical simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-femtosecond period matching that of the observed vibrational modes. Our results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound reference system.