A recalculation of the efficiency limit in crystalline Si/Si tandem solar cells

We determine the limiting efficiency for monolithic tandem solar cells that employ crystalline silicon for the topcell as well as for the bottom cell. In such a design, the top-cell extends over the region of very high generation rate that forms at the front of the device. Consequently, the design benefits from a high excess carrier density in the top-cell, resulting in a voltage in the tandem device that is more than twice the voltage of equally thick single junction solar cells. Considering Coulomb-enhanced Auger recombination coefficient, we find a maximum efficiency of 30.7% for a total device thickness of 500 mu m wherein the top cell thickness amounts to 2.15 mu m, representing gain of 1.1% (abs) with respect to the limiting efficiency of single junction devices.

Automated summary

The study determined the limiting efficiency of monolithic tandem solar cells using crystalline silicon for both the top and bottom cells, showing a significant advantage in terms of voltage and efficiency.