Heterojunction organic photovoltaic cells as molecular heat engines: A   simple model for the performance analysis
  Organic heterojunction solar cells are analyzed within a minimal model that includes the essential physical features of such systems. The dynamical properties of this model, calculated using a master equation approach, account for the qualitative behavior of such systems. The model yields explicit results for current-voltage behavior as well as performance characteristics expressed in terms of the thermodynamic efficiency as well as the power conversion efficiency at maximum power, making it possible to evaluate the optimal setup for this device model. 
Mario Einax, Marcel Dierl, Abraham Nitzan
cond-mat.mtrl-sci cond-mat.mes-hall