Figure 1
From: The Molecular Photo-Cell: Quantum Transport and Energy Conversion at Strong Non-Equilibrium

Schematic illustration of the minimal model for a molecular PV cell.
The system consists of a molecule donor and an acceptor molecule, characterized by their HOMO and LUMO levels and coupled to each other via electron hopping. The D-molecule is coupled only to the left electrode and the A-molecule only to the right electrode. Electrons in the donor interact with both photons (wiggly line) and phonons (broken line).