Impact of threshold energy of multiple exciton generation solar cells

The threshold energy (E_th) over 100% quantum yield (QY) is a key factor to determine the performance of multiple exciton generation (MEG) solar cells. By investigating non-idealities of MEG models, it is critical to consider non-idealities in E_th for the onset of MEG processes. Detailed balance calculations show that despite a large experimental emphasis on the maximum quantum yield, the threshold energy has a substantial and significant effect. The first effect is that at threshold energies between 2 and 3Eg (for one sun) or 3 and 4Eg for maximum concentration, even theoretical benefits of the MEG process disappear. Since measured values are within this range, this is an important effect to consider. The second effect is that the inclusion of non-ideal threshold energies increases the optimum band gap, moving to values consistent with silicon.