Thermodynamics of losses in photovoltaic conversion

This letter presents a thermodynamic analysis of losses in an ideal solar cell. It is shown that the maximum voltage—corresponding to the voltage produced by a hot-carrier solar cell—is equal to the energy of the incident solar photon multiplied by the appropriate Carnot factor. Voltage generated by the usual p-n junction cell is lower on account of entropy generation through kinetic losses, photon cooling, and étendue expansion of the incident beam. Simple expressions can be obtained by an approximation where the energy and entropy changes are modeled by the corresponding expressions for a two-dimensional ideal photon gas.