Exciton dissociation mediated by phonons in organic photovoltaics

Abstract

It is well known that phonons can overscreen the bare Coulomb electron-electron repulsion, turning it into the effective attraction that binds the Cooper pairs responsible for BCS superconductivity. Here, we use a simple lattice model to prove that the counterpart of this is also possible, whereby phonons overscreen the bare electron-hole attraction and may turn it repulsive at short distances, driving exciton dissociation in certain regions of the parameter space. We argue that this phonon-mediated short-range screening plays an important role in the physics of organic solar cell materials (and other materials with strong electron-phonon coupling) and could point the way to new strategies for optimizing their efficiencies.

11 pages, 6 figures

References in corpus (8)

• Green's function of a dressed particle
• The Green's Function of the Holstein Polaron
• Systematic improvement of the Momentum Average approximation for the Green's function of a Holstein polaron
• The polaron paradigm: a dual coupling effective band model
• Trapping of three-dimensional Holstein polarons by various impurities
• Exact treatment of exciton-polaron formation by Diagrammatic Monte Carlo
• Strongly bound yet light bipolarons for double-well electron-phonon coupling
• Lattice exciton-polaron problem by quantum Monte Carlo simulations