A comparison of 3rd generation solar cell efficiencies using thermodynamic transfer functions: Which method is best?

Exceeding the Shockley-Queisser efficiency limit for a single junction solar cell has been theorized using various means. Specifically, up- and down-conversion, carrier multiplication and intermediate band transitions have been posited as methods of improving the efficiency. Here, we compare these methods using a thermodynamic approach with a newly devised pseudo-linear system model. This method allows a schematic interpretation of the internal processes of efficiency enhancement techniques. In particular, we demonstrate that down-conversion is thermodynamically preferable to carrier multiplication, and that splitting the sun's spectrum before impinging upon the solar cell is preferable to attempting to do this within the solar cell itself.