Entropy production in a p-n photovoltaic converter
  The case of a non-biased (light excited) p-n photo-voltaic (PV) cell working in a closed circuit with a resistive load is investigated by means of irreversible thermodynamics in the linear range. To our knowledge, this is the first time that both electronic processes, such as photo-excitations, carrier diffusions and recombinations, and electrical processes, such as current generation and the Joule effect, are considered together in the context of thermodynamics. An equation for the built-up voltage is obtained where the recombination resistance of the diode and a collection factor of the photo-carriers, depending on the thickness of the illuminated cell-side, are included in a natural way.depending on the thickness of the illuminated cell-side, are included in a natural way. The case of a biased PV-cell is also considered concerning the empirical parallel resistance introduced in realistic models. Some insights into its real meaning have been obtained. 
M. Salis, P. C. Ricci, F. Raga, F. Quarati