Abstract
This contribution gives an overview of our recent study of phonon driven exciton dissociation at semiconductor polymer heterojunctions, using a quantum dynamical analysis based on a linear vibronic coupling model parametrized for three electronic states and 20-30 phonon modes. The decay of the photogenerated exciton towards an interfacial charge transfer state is an ultrafast (femtosecond to picosecond scale) process which initiates the photocurrent generation. We consider several representative interface configurations, which are shown to exhibit an efficient exciton dissociation. The process depends critically on the presence of intermediate states, and on the dynamical interplay between high-frequency (C=C stretch) and low-frequency (ring-torsional) modes. The dynamical mechanism is interpreted in terms of a hierarchical electron-phonon model which allows one to identify generalized reaction coordinates for the nonadiabatic process. This analysis highlights that the electron-phonon coupling is dominated by the high-frequency modes, but the low-frequency modes are crucial in mediating the transition to a charge-separated state. The ultra-fast, highly nonequilibrium dynamics is in accordance with spectroscopic observations.
Original language | English |
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Pages (from-to) | 138-143 |
Number of pages | 6 |
Journal | AIP Conference Proceedings |
Volume | 1102 |
DOIs | |
Publication status | Published - 2009 May 12 |
Event | Theory and Applications of Computational Chemistry, TACC 2008 - Shanghai, China Duration: 2008 Sep 23 → 2008 Sep 27 |
Keywords
- Excitons
- Optoelectronics
- Semiconducting polymer materials
- Vibronic coupling
ASJC Scopus subject areas
- Physics and Astronomy(all)