Thermodynamic limit on the open circuit voltage of solar cells

A new thermodynamic limit for the open circuit voltage of solar cells that includes thermalization is obtained in terms of photon entropy. A simple graphical construction makes it possible to link this limit to the existing limits for single junction cells due to Trivich and Flinn, Shockley and Queisser and W\"urfel, and the thermodynamic Carnot-type limit for hot-carrier solar cell. At the fundamental level, this limit points to similarity between photovoltaic and thermoelectric energy conversion.