Model for the dynamics of carrier injection in a band with polaronic states: Application to exciton dissociation in organic solar cells

Abstract

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.

References in corpus (9)

• Polymer-Fullerene Bulk Heterojunction Solar Cells
• Entropy and disorder enable charge separation in organic solar cells
• Dynamical mean-field theory of the small polaron
• Polaron band formation in the Holstein model
• Electron-phonon coupling in the C60 fullerene within the many-body GW approach
• On the self-trapping problem of electrons or excitons in one dimension
• Dynamical Properties of small Polarons
• Impact of quantized vibrations on the efficiency of interfacial charge separation in photovoltaic devices
• Inhomogeneous dynamical mean field theory of the small polaron problem

Cited by in corpus (1)

• Exciton dissociation in organic solar cells: An embedded charge transfer state model