学术文献库

We develop a quantum model for the dynamics of carrier injection in a band that presents a strong carrier-vibration coupling. This coupling modifies the spectral density of the band and can even create pseudo-gaps that sign the onset of polaronic states. The injection of a carrier that interacts with many vibration modes is a complex many-body process that is treated by combining the quantum scattering theory and the Dynamical Mean-Field Theory (DMFT). For the model analysed here, which is adapted to compact phases, the number Z of neighbors of a given site is large and in this limit the DMFT becomes exact. The model is applied to the excitonic dissociation at the donor-acceptor interface for organic solar cells. The main ingredients are the electron-hole Coulomb interaction, the recombination process and the existence of polaronic states in the acceptor band. Using parameters extracted from ab-initio calculations we analyze the spectral density on the charge transfer state (CTS), the average energy transfered to phonons on the CTS and the quantum yield of the injection process. We find in particular that, even with a strong electron-vibration coupling, one can get a vibrationally cold charge transfer state with a high injection yield as often observed experimentally.