THE CARNOT FACTOR IN SOLAR-CELL THEORY

In a two-level system the open circuit voltage or difference between t he electro-chemical potentials at the contacts, is related to the ener gy gap E-g by a Carnot factor; V = (1 - T-s/T-p)E-g. Here, T-s and T-p are the absolute temperatures of the ambient (surroundings) and of th e incident blackbody radiation (''pump''), respectively. A simple two- step statistical thermodynamic argument is given here which makes this result plausible. Its standing in a more general context is also disc ussed. (C) 1998 Elsevier Science Ltd. All rights reserved.